AltaFoam Monitor Optimization Chemical Engineering

Transcription

AltaFoam Monitor Optimization
Study of the repeatability of the AltaFoam Monitor testing equipment,
measuring pressure, expansion, temperature and curing of
one-component polyurethane systems dispensed out of an aerosol can
and applied by a dispensing gun or straw adapter at different ambient
conditions
Ana Filipa Ferreira da Silva Dionisio
Dissertation for obtaining the degree of Master in
Chemical Engineering
Jury
President:
Prof. Sebastião Alves
Supervisor:
Prof. João Carlos Moura Bordado
Supervisor:
Mr. Aster de Schrijver
Vogal:
Prof. António José Boavida Correia Diogo
November 2009
Acknowledgements
I would like to thank Professor João Moura Bordado, my supervisor at Instituto Superior Técnico and
Mr. Aster de Schrijver, the President of Altachem NV, for giving me the opportunity to take my
academic training in his company.
I would also like to thank Sven De Vis, chemical engineer at Altachem NV, for his hard work and
dedication to manage and stimulate my work and that of the other internees at Altachem and also for
continuing to help me during the process of writing this thesis.
A special word of gratitude to Professor José M. Cardoso de Menezes, at Instituto Superior Técnico, for
his time and enlightening me in the subject of Chemometrics.
To Ana Luísa, Andreia, Duarte, Inês, João, Maria, Pedro, Sandra e Vítor: thank you for the spiral of good
times.
To Artur, thank you for the patience and support.
Finally, I would like to thank my parents for everything.
i
Resumo
O AltaFoam Monitor é um aparelho com a forma de um molde construido para monitorizar o processo
de cura de espumas de poliuretanos de um componente. Através de sensores incorporados, mede e
monitoriza quatro variáveis: altura da espuma dispensada, pressão desenvolvida, cura e temperatura.
Com o intuito de validar estas medições, realizou-se um estudo da repetibilidade recorrendo a três
formulações diferentes, submetidas a dois períodos de maturação, em testes realizados a duas
temperaturas de lata/cura com duas larguras de molde. As variáveis analisadas são a pós-expansão,
pressão máxima desenvolvida, ângulo de cura e temperatura mínima e máxima.
Foi utilizado um método estatístico para determinar a existência de repetibilidade das variáveis
referidas, baseado no cálculo do desvio-padrão da amostra e do limite de repetibilidade.
Foi também estudada a influência de algumas variáveis químicas no processo de cura, nomeadamente
de dois catalisadores e do índice de excesso de NCO:OH, e a sua detecção pelo AltaFoam Monitor.
As formulações feitas para este propósito foram também sujeitas a testes rápidos em papel e em
molde de madeira, e os resultados destes últimos foram comparados com a análise das espumas
dispensadas no AltaFoam Monitor, com o objectivo de determinar a existência de equivalência entre
os dois moldes.
Palavras-chave: espuma de poliuretano de um componente, monitorização, altura, pressão, cura,
temperatura, repetibilidade
ii
Abstract
The AltaFoam Monitor is a mould-like apparatus that was designed to monitor the process of curing of
one-component polyurethane foams. Using built-in sensors it measures and monitors four variables:
height of the sprayed bead, developed pressure, curing and temperature.
In order to validate those measurements, a repeatability study was carried out using three different
formulations submitted to two different aging periods at two different can/curing temperatures using
two mould gap sizes. The variables analyzed were post-expansion, maximum developed pressure,
curing angle and minimum and maximum temperatures.
A statistical method was used to assess the repeatability of said variables, based on the calculation of
the sample standard deviation and of the repeatability limit.
The influence of certain chemical variables in the curing process was also studied, namely two
catalysts and the index of excess NCO:OH and its detection by the AltaFoam Monitor.
The formulations made for this purpose were also subjected to quick tests in paper and in wooden
mould, and the results of the latter ones were compared to the analysis of the beads from the
AltaFoam Monitor, to search for equivalency between the two moulds.
Keywords: one-component polyurethane foam, monitor, post-expansion, pressure, curing,
temperature, repeatability
iii
Contents
Acknowledgements .................................................................................................................................... i
Resumo ...................................................................................................................................................... ii
Abstract .................................................................................................................................................... iii
Abbreviations............................................................................................................................................. x
1
Introduction ....................................................................................................................................... 1
2
Theoretical background ..................................................................................................................... 2
3
2.1
Polyurethanes history and market ........................................................................................... 2
2.2
Basic polyurethane chemistry .................................................................................................. 3
2.3
The OCF foaming process ......................................................................................................... 5
2.4
Raw materials ........................................................................................................................... 6
2.4.1
Isocyanates .......................................................................................................................... 6
2.4.2
Polyols .................................................................................................................................. 6
2.4.3
Chain extenders and crosslinkers ........................................................................................ 8
2.4.4
Catalysts ............................................................................................................................... 8
2.4.5
Blowing agents ..................................................................................................................... 9
2.4.6
Flame retardants................................................................................................................ 10
2.4.7
Silicone surfactants ............................................................................................................ 10
Materials and methods.................................................................................................................... 12
3.1
Reagents and additives .......................................................................................................... 12
3.2
Employed formulations .......................................................................................................... 12
3.3
The AltaFoam Monitor ........................................................................................................... 13
3.3.1
Overview ............................................................................................................................ 13
3.3.2
The temperature sensor and interpretation of temperature measurements in the AFM 14
3.3.3
The distance sensor and interpretation of post-expansion measures in AFM .................. 15
3.3.4
The curing sensor and interpretation of curing measurements in AFM ............................ 16
3.3.5
The pressure sensor and interpretation of pressure measurements in AFM .................... 17
3.4
Variability in analytical measurements .................................................................................. 18
3.5
Quick tests .............................................................................................................................. 21
iv
4
3.5.1
Froth/foam output testing ................................................................................................. 21
3.5.2
Horizontal paper test ......................................................................................................... 22
3.5.3
Horizontal mould test ........................................................................................................ 23
Experimental results ........................................................................................................................ 25
4.1
Overview ................................................................................................................................ 25
4.2
Determination of outliers ....................................................................................................... 26
4.3
Sample size ............................................................................................................................. 26
4.4
Results of the repeatability trials ........................................................................................... 29
4.5
Verification of the results of the previous study of the AFM ................................................. 38
4.6
Influence of chemical variables in the curing process ........................................................... 39
4.6.1
Overview ............................................................................................................................ 39
4.6.2
Results of the NIAX series at 23/23ºC ................................................................................ 41
4.6.3
Results of the DMDEE series at 23/23ºC ........................................................................... 45
4.6.4
Results of the index of excess NCO:OH series at 23/23ºC ................................................. 48
4.6.5
Results of the NIAX series at 5/5ºC .................................................................................... 52
4.6.6
Results of the DMDEE series at 5/5ºC ............................................................................... 55
4.6.7
Results of the index of excess NCO:OH series at 5/5ºC ..................................................... 58
5
Future developments ...................................................................................................................... 60
6
Conclusions ...................................................................................................................................... 61
7
Bibliography ..................................................................................................................................... 62
8
Appendix .......................................................................................................................................... 64
Appendix 1.
Sample size for the calculation of AFM curing variables........................................... 64
Appendix 2.
Standard procedure for spraying in AltaFoam Monitor ............................................ 67
Appendix 3.
Results of the repeatability trials .............................................................................. 68
Appendix 4.
Results of the repeatability trials for previous study on the AltaFoam Monitor ...... 75
Appendix 5.
Results of quick tests of formulation 6459 GWMB3 ................................................. 76
v
Index of figures
Figure 2.1 Worldwide consumption of polyurethane products ................................................................ 2
Figure 2.2 Market share of the polyurethane consuming industries ........................................................ 2
Figure 2.3 Worldwide consumption of polyurethanes .............................................................................. 3
Figure 2.4 The carbamate functional group .............................................................................................. 3
Figure 2.5 Schematic representation of polyurethanes structure ............................................................. 4
Figure 2.6 Resonance structures of isocyanate ......................................................................................... 4
Figure 2.7 Formation of a urethane linkage from the reaction between a diisocyanate and a diol ......... 4
Figure 2.8 Prepolymer reaction with water and formation of urea groups .............................................. 4
Figure 2.9 Formation reaction of allophanate ........................................................................................... 5
Figure 2.10 Formation reaction of biuret .................................................................................................. 5
Figure 2.11 Formation reaction of isocyanate ........................................................................................... 6
Figure 2.12 Molecular structure of MDI .................................................................................................... 6
Figure 2.13 Polyether polyols: a) polypropylene glycol (PPG) and b) polyethylene glycol (PEG) .............. 7
Figure 2.14 Structure of a polyester polyol obtained by condensation of ethylene glycol and adipic acid
................................................................................................................................................................... 7
Figure 2.15 Schematic representation of a polyurethane chain ............................................................... 8
Figure 2.16 Structure of the bis-(2-dimethylaminoethyl-) ether molecule ............................................... 9
Figure 2.17 Structure of 2,2-dimorpholinodiethylether ............................................................................ 9
Figure 2.18 Molecular structure of tric-chloropropylphosphate ............................................................. 10
Figure 3.1 Temperature sensor ............................................................................................................... 14
Figure 3.2 Typical temperature profile measured with AltaFoam Monitor ............................................ 14
Figure 3.3 Distance sensor ....................................................................................................................... 15
Figure 3.4 Profile of the curing process measured with the AltaFoam Monitor ..................................... 16
Figure 3.5 Curing sensor .......................................................................................................................... 17
Figure 3.6 Pressure profile measured with AFM ..................................................................................... 18
Figure 3.7 Pressure sensor ....................................................................................................................... 18
Figure 3.8 Distribution of differences between two test results ............................................................. 20
Figure 3.9 Schematic representation of a wooden mould used in horizontal mould tests ..................... 23
Figure 4.1 Schematic representation of a box and whiskers plot............................................................ 26
Figure 4.2 Sample size for post-expansion as a function of the error ..................................................... 28
Figure 4.3 Sample size for alpha as a function of the error ..................................................................... 28
Figure 4.4 Sample size for maximum pressure as a function of the error ............................................... 29
Figure 4.5 Post-expansion as a function of liquid in can ......................................................................... 33
Figure 4.6 Curing angle alpha as a function of the initial height of the bead .......................................... 33
vi
Figure 4.7 Post-expansion as a function of liquid in can for formulation 1612 AWMB3 with 1 day of
aging, in a 2 cm mould gap and a can/curing temperature of 23/23ºC and of 5/5ºC ............................. 37
Figure 4.8 Curing angle alpha of formulation 6396 as a function of liquid in can for 2 cm and 3 cm
mould gaps .............................................................................................................................................. 37
Figure 4.9 Post-expansion of formulation 6396 as a function of liquid in can for 2 cm and 3 cm mould
gaps.......................................................................................................................................................... 38
Figure 4.10 Post-expansion as a function of %LIC for gun formulation 6396 GEMB3 and adapter
formulation 1612 AWMB3 with 5 days of aging, a can and curing temperature of 23ºC and a 3 cm
mould gap ................................................................................................................................................ 38
Figure 4.11 NIAX series at 23/23ºC.......................................................................................................... 41
Figure 4.12 Foam analysis of formulations of the NIAX series, in paper and in wooden mould, at
23/23ºC.................................................................................................................................................... 42
Figure 4.13 Foam analysis of formulations of the NIAX series, in AFM mould, with a 3 cm mould gap, at
23/23ºC.................................................................................................................................................... 43
Figure 4.14 Overal mould density (wooden mould) of formulations of the NIAX series......................... 44
Figure 4.15 DMDEE series at 23/23ºC ..................................................................................................... 45
Figure 4.16 Foam analyses of the formulations of the DMDEE series, in paper and in wooden mould, at
23/23ºC.................................................................................................................................................... 46
Figure 4.17 Foam analysis of the formulations of the DMDEE series, in AFM mould, with a 3 cm mould
gap, at 23/23ºC ........................................................................................................................................ 47
Figure 4.18 Overall density mould (wooden mould) for the formulations of the DMDEE series ............ 48
Figure 4.19 Index series at 23/23ºC ......................................................................................................... 49
Figure 4.20 Foam analysis of the formulations of the Index series in paper and in wooden mould at
23/23ºC.................................................................................................................................................... 50
Figure 4.21 Foam analysis of the formulations of the Index series in AFM mould, with a 3 cm mould
gap, at 23/23ºC ........................................................................................................................................ 51
Figure 4.22 Overall mould density (wooden mould) for the formulations of the Index series ............... 51
Figure 4.23 NIAX series at 5/5ºC.............................................................................................................. 52
Figure 4.24 Foam analysis of the formulations of the NIAX series, in paper and in wooden mould, at
5/5ºC ........................................................................................................................................................ 53
Figure 4.25 Foam analysis of formulations of the NIAX series, in AFM mould, at 5/5ºC ........................ 54
Figure 4.26 Output liquid for formulations of the NIAX series ................................................................ 54
Figure 4.27 DMDEE series at 5/5ºC ......................................................................................................... 55
Figure 4.28 Foam analysis of the formulations of the DMDEE series, in paper and in wooden mould, at
5/5ºC ........................................................................................................................................................ 56
Figure 4.29 Foam analysis of the formulations of the DMDEE series, in AFM mould, at 5/5ºC .............. 57
Figure 4.30 Output liquid for the formulations of the DMDEE series ..................................................... 57
vii
Figure 4.31 Foam analysis of the formulations of the Index series, in paper and in wooden mould, at
5/5ºC ........................................................................................................................................................ 58
Figure 4.32 Output liquid for the formulations of the Index series ......................................................... 59
Figure 5.1 Representation the three principal components of a PCA analysis of formulations 1612
AWMB3, 2631 AWB3 and 6396 GEMB3 .................................................................................................. 60
Figure 8.1 Foam analysis of the formulations of base formulation 6459 GWMB3, in paper and in
wooden mould, at 23/23ºC and at 5/5ºC ................................................................................................ 76
viii
Index of tables
Table 2.1 Boiling points of blowing agents used in OCF production ......................................................... 9
Table 3.1 Reagents and additives employed in this work ....................................................................... 12
Table 3.2 Formulations used in the repeatability trials ........................................................................... 12
Table 3.3 Formulations of the NIAX, DMDEE and Index series ................................................................ 13
Table 3.4 Description of the foam properties rating syspem used in this work ...................................... 22
Table 4.1 Results of the repeatability trials in adapter foam 1612 AWMB3: 1 day of aging; can/curing
temperature: 23ºC/23ºC; 2 cm mould gap.............................................................................................. 30
Table 4.2 Summary of the repeatability results of each trial for each analyzed variable ....................... 32
Table 4.3 Influence of initial bead height on Cstart and Cmin ..................................................................... 34
Table 4.4 Relation between curing angle Alpha and Pmax ........................................................................ 35
Table 4.5 Results of the repeatability of beads with LIC between 40% and 60% of formulation 1612
AWMB3 with 5 days of aging in a 2 cm mould gap with the previous model of the AltaFoam Monitor 39
Table 4.6 Repeatability results for beads with %LIC between 40% and 60% .......................................... 39
Table 4.7 Results of AFM measurements of NIAX, DMDEE and Index series at a can/curing temperature
of 23/23ºC ............................................................................................................................................... 40
of 5/5ºC ................................................................................................................................................... 40
ix
Abbreviations
PU – Polyurethane
OCF – One Component Foam
MDI – Diphenylmethane Diisocyanate
DME – Dimethylether
LPG – Liquefied Petroleum Gas
FCA – Foam Controlling Additives
AFM – Alta Foam Monitor
PEtot –Post-expansion
Tmin – Minimum temperature
Tmax – Maximum temperature
Pmax – Maximum pressure
%LIC – Percentage of liquid in can
NAC – Non Acceptable
AC – Acceptable
P – Paper
M – Mould
SR – Shaking Rate
SS – Surface Structure
GB – Glass Bubbles
CS – Cell Structure
V&PH – Voids and Pin Holes
BH – Base Holes
CC – Cell Collapse
SBH – Side Base Holes
ODM – Overall Density Mould
x
1 Introduction
Polyurethanes are a class of polymers that have been expanding in production volume and in range of
applications for decades. One-component polyurethane foams, and specifically their curing process,
are a very complex system, highly sensible to chemical composition and dependent of environmental
factors, such as temperature and humidity. The use of a device that can monitor several aspects of the
curing process can be very important to the development, improvement and quality control of onecomponent polyurethane foams.
The present thesis reports the research carried in order to fulfill the degree of Master of Science in
Chemical Engineering of Instituto Superior Técnico. The research intended to study the existence of
repeatability of the analyzed variables: post-expansion, curing angle, maximum developed pressure
and minimum and maximum temperatures in the AltaFoam Monitor, an apparatus that monitors the
process of curing of one-component polyurethane foams. The procedure is based on a statistical
method that assumes that the tests are carried under repeatability conditions in order to calculate a
sample standard deviation and a repeatability limit. The tests were performed at two different
can/curing temperatures on three different formulations submitted to two different aging periods,
using two mould gap sizes. The results obtained were compared to the results of a previous similar
study. The relation between some curing variables and their dependence on test settings is also object
of study.
Furthermore, the influence of certain chemical variables in the curing process was studied using the
AltaFoam Monitor and an analysis was made to the beads sprayed in the AltaFoam Monitor’s steel
mould and compared to the beads of the same formulations sprayed in the recurrently used wooden
mould in order to determine the existence of equivalency between the two moulds.
This document is divided into sections and subsections. Section 2 gives an overview of the theoretical
backgrounds of polyurethanes history, market, basic chemistry and the main compounds used in its
manufacture. Section 3 gives a detailed description of the AltaFoam Monitor and its built-in sensors, as
well as a description of the statistical method used in the determination of the existence of
repeatability. Section 4 presents and discusses the results by means of tables and figures. A different
approach on the study of the curing process is suggested in section 5 and the main conclusions
achieved are stated in section 6.
1
2 Theoretical background
2.1 Polyurethanes history and market
The fundamental addition polymerization reaction of diisocyanates with alcohols to produce high
urethane polymers was discovered in 1937 by Otto Bayer and coworkers in the laboratories of the
German I. G. Farben Industrie as a competitive response to Carothers' work on polyamides, or nylons,
at E. I. du Pont. Since then, polyurethanes have developed as a unique class of materials and have
found use in a wide variety of applications. Besides incorporating the urethane linkage, these materials
also sometimes contain several other types of linkages such as amide, urea, ether, and ester. By
controlling variables such as the functionality, chemical composition, and the molecular weight of the
different reactants, a wide class of materials with significantly varying properties can be obtained. This
flexibility has led polyurethanes to find use as synthetic polymers in foams, accounting for over half of
overall polymeric foam production, elastomers, coatings, sealants, and adhesive based products (1).
1000 ton
14000
12000
10000
8000
6000
4000
2000
0
2000
Flexible foams
2005
Rigid foams
CASE
Adhesives
Total
Figure 2.1 Worldwide consumption of polyurethane products
Figure 2.2 Market share of the polyurethane consuming industries
2
Some of the applications of polyurethanes lie in the automotive, furniture, construction, thermal
insulation, and footwear industries.
1000 ton
14000
12000
10000
8000
6000
4000
2000
0
2000
South America
China
Middle East & Africa
North America
2005
Asia Pacific
Europe
Figure 2.3 Worldwide consumption of polyurethanes
The polyurethanes world market grew from 10 million tones in the year 2000 to 13,6 million tones in
2005 at a rate of 6,7% per year. In 2005 polyurethanes were the sixth most consumed polymers, with
a 5% market share (2).
2.2 Basic polyurethane chemistry
The polymers known as polyurethanes include materials that incorporate the carbamate group, as well
as other functional groups, such as ester, ether, amide and urea. The name polyurethane is derived
from ethyl carbamate, known as urethane (3).
Figure 2.4 The carbamate functional group
Polyurethanes have the following structure, where urethane groups alternate with organic radicals:
3
Figure 2.5 Schematic representation of polyurethanes structure
Polyurethanes can be synthesized through the isocyanate reactions in the presence of a catalyst and
other additives. The electronic structure of the isocyanate group can be represented by several
resonance structures, as illustrated by figure 2.6:
Figure 2.6 Resonance structures of isocyanate
The addition reaction between an isocyanate and an alcohol with hydrogen displacement to give a
urethane has been known since 1849 (Wurtz). The principal of the polymer chemistry conceived by
Otto Bayer in 1937 is the extension of this reaction to di- and polyfunctional isocyanates and hydroxy
compounds resulting in the formation of linear, branched, or crosslinked polymers (4).
Polyurethane foams are made from isocyanate-terminated prepolymers prepared according to the
reaction below using excess diisocyanate.
Figure 2.7 Formation of a urethane linkage from the reaction between a diisocyanate and a diol
When the froth is dispensed, the prepolymer reacts with water (moisture from the air, etc), which
causes an increase in molecular weight by formation of urea groups with simultaneous loss of carbon
dioxide:
Figure 2.8 Prepolymer reaction with water and formation of urea groups
As the evolved gas causes the polymer to foam, the polymerization reaction increases the viscosity
and sets the foam before it collapses (5).
The urethane groups in the polymer chain can react further with excess isocyanate to form branched
molecules: allophanates from urethanes, biurets from ureas (6). These secondary reactions also take
4
place inside the aerosol can, although they occur to a much less extent than the primary reactions due
to the lower reactivity of the active hydrogens in ureas and urethanes. However, their importance
must not be under-estimated: the formation of allophanates, and particularly biurets, is responsible
for crosslinking and branching which has an important effect on polyurethane foam properties in
many instances (1), including the decrease of the shelf life of the product. Figures 2.9 and 2.10 show
the formation reactions of allophanates and biurets.
Figure 2.9 Formation reaction of allophanate
Figure 2.10 Formation reaction of biuret
2.3 The OCF foaming process
In a one-component foam system (OCF), the polyol, the isocyanate, catalyst, surfactants, and blowing
agents are mixed together in a closed container. When the polyol blend and the iocyanate are mixed
together, the prepolymerization reaction starts. In OCF the isocyanate compound (MDI) is not used in
the stoichiometric quantitty. The excess of it will react with the atmospheric moisture once the froth is
dispensed from the can. The froth will then expand and cure, forming polyurea and CO 2.
The foaming process is divided into four stages.
The first stage, which takes place inside an aerosol can, comprises a liquid mixture constituted by
polyol blend, isocyanate, additives and blowing agent. When these different constituents are mixed
inside a can, the pre-polymerisation reaction starts and the pre-polymer is produced.
The second stage occurs when dispensing the foam: the pre-polymer starts to expand due to the
vaporization of the blowing agent and a low-density froth is then formed.
5
The third stage arises due to the presence of water content in the surrounding environment (moisture
in air or substrate), which causes the froth to begin to cure. In the reactions that take place while the
froth is curing there is the production of CO2, which is responsible for the expansion of the foam.
The fourth stage corresponds to a low-density cured foam in the end of the foaming process (7).
2.4 Raw materials
2.4.1
Isocyanates
The isocyanate permits the NCO groups to react with functional groups from the polyol, water, and
crosslinkers in the formulation. All isocyanates used in industry today contain at least two NCO groups
per molecule. The most commercially viable methods of producing isocyanates involve amine
phosgenation (3), as shown in figure 2.11.
Figure 2.11 Formation reaction of isocyanate
The two most common sources of isocyanate functionalities in foam production come from toluene
diisocyanate (TDI) and diphenylmethane-4:4’-diisocyanate (MDI), of which the former is more
commonly used in North America, where as the latter one has a greater market demand in European
countries (8).
Figure 2.12 Molecular structure of MDI
As a general rule, the isocyanates are hard segments that impart rigidity to the polymer. The polyol is
the so-called soft segment (9).
2.4.2
Polyols
There are two main polyols used in the foam industry: polyether polyols and polyester polyols.
6
A polyether polyol is the polymeric reaction product of an organic oxide and an initiator compound
containing two or more active hydrogen atoms. The active hydrogen compound in the presence of a
base catalyst initiates ring opening and oxide addition. Oxide addition is continued until the desired
molecular weight is obtained. If the initiator has two active hydrogens, a diol is formed. If a
trifunctional initiator such as glycerine is used, oxide addition produces chain growth in three
directions originating a triol. These reactions are exothermic. The addition of propylene oxide, for
example, releases approximately 22 kcal/mol. Many initiator compounds, as well as blends of these
compounds, are used for the manufacture of flexible foam polyols (3). Among the polyether polyols,
the polypropylene glycols (PPGs) are the most commonly used.
a)
b)
Figure 2.13 Polyether polyols: a) polypropylene glycol (PPG) and b) polyethylene glycol (PEG)
Polyester polyols are produced by polycondensation of a diacid with excess diol. Depending on the
acid, the resulting polyester polyol will have different properties. The most used acids are: adipic acid,
which confers flexibility and phtalic acid or phtalic anhydride, which confers rigidity to the polyol
chains (10).
Figure 2.14 Structure of a polyester polyol obtained by condensation of ethylene glycol and adipic acid
The type of polyol defines the physical properties of the final foam. In one-component foam, with built
in resilience, it will require some stiffness of the polymer network so that overall rigidity is imparted to
the foam. The polymer properties are primarily met by the degree of crosslinking, and, in turn, this is
achieved by an appropriate choice of both molecular weight and functionality of the polyol used for
coupling with the isocyanate (11).
Historically, primary containing hydroxyl groups compounds, whether polyether or polyesters, are
avoided in one-component foam applications because they tend to yield rapid temperature increase
and high maximum exotherm (10).
7
2.4.3
Chain extenders and crosslinkers
To gain their optimum mechanical and processing properties, thermoset polymers must have a good
balance of structure of chains and linkages. The backbone structure depends on the monomers or
prepolymers but can be modified with low-molecular weight species named chain extenders. A chain
extender is a low-molecular difunctional species that can react to form a linear extended structure and
it has a direct influence on the distribution of both hard and soft segments in the polyurethane
polymer. The most commonly used chain extenders are and glycols, diamines and hydroxy amines
(12).
Diisocyanate
Chain extender
Polyol
Figure 2.15 Schematic representation of a polyurethane chain
In figure 2.15 is it possible to identify different fractions of the chain where one is predominantly the
result obtained by the reaction of diisocyanate with the chain extender and the other the sequence
obtained by the reaction of diisocyanate molecules with polyol.
The links between macromolecules are formed by reaction with crosslinkers that can react with the
functions of two separate macromolecules. Crosslinkers are tri- and other multifunctional entities that
can react to form a tridimensional network.
2.4.4
Catalysts
Virtually all commercially manufactured flexible polyurethane foams are made with the aid of at least
one catalyst. Various combinations of catalysts are used to establish an optimum balance between the
chain propagation (isocyanate with hydroxyl) reaction and blowing (isocyanate with water) reactions.
The polymer formation rate and the gas formation rate must be balanced so that gas is entrapped
efficiently in the gelling polymer and the cell walls develop sufficient strength to maintain their
structure without collapse or shrinkage. Catalysts are also important for assuring completeness of
reaction or “cure” in the finished foam (3).
Tertiary amines are the most common catalysts and are used for the catalysis of the isocyanate and
polyol reaction that forms the polyurethane and also the expansion reaction with water. An example is
bis-(2-dimethylaminoethyl-) ether, used as a mixture with 30% dipropylene glycol, known as NIAX A1.
8
Figure 2.16 Structure of the bis-(2-dimethylaminoethyl-) ether molecule
Most catalysts cause thickening and a tendency for gelation. Adding too much catalyst reduces shelf
life of the prepolymer and will originate coarse foams. The latest catalyst used in most OCF
formulations today is DMDEE (2,2-dimorpholinodiethylether).
Figure 2.17 Structure of 2,2-dimorpholinodiethylether
2.4.5
Blowing agents
Polymeric expansion results from the release of gaseous compounds during polymerization/froth
dispensing by means of chemical and physical blowing processes. In the chemical blowing process CO2
is formed by the reaction between water and isocyanate. The physical blowing process involves the
use of blowing agents, which are a mixture of low boiling solvents, inert towards chemical reactions,
producing bubbles in the froth due to their evaporation when dispensed. They create gas pressure in
the container and act as a propellant forcing the prepolymer to exit the can. Addition of a physical
blowing agent while maintaining the water/isocyanate content constant typically results in larger cells
and a greater degree of cell openness, which results in a decreased foam density generally leading to
an increase in foam softness.
Chlorofluorocarbons used to be the major blowing agents, but when it was discovered that certain
CFC´s can damage the environment, hydrochlorofluorocarbons (HCFCs) started being used as
replacements, although they too have ozone depleting potential. Today the most common gases used
are diemethylether (DME) and liquid petroleum gas (LPG), which consists of mixtures of butane, isobutane and propane. Usually the combination of polar and apolar blowing agents gives optimal
solvency power.
Table 2.1 Boiling points of blowing agents used in OCF production
Blowing agent
Boiling point (ºC)
Propane
Dimethyl ether
Iso-butane
Butane
-42
-24,8
-12
-0.5
9
2.4.6
Flame retardants
Polyurethanes, like all other organic materials, will burn in the presence of oxygen and sufficient heat.
Flame-retardants are compounds used to delay the initial ignitability, burning rate and smoke
evolution.
The physical state of the polymer is very important: low density, open cell foams, having a large
surface area and high permeability to air, are more flammable. One-component foam, for instance, is
a semi-rigid foam and due to its highly cross linkage is less flammable than flexible foams.
In PU flexible foams, the most widely used flame retardants are the chlorinated phosphate esters and
chlorinated paraffins, but other compounds containing phosphorous, halogens, boron, sulphur,
antimony and various other metals are also used.
Flammability can be reduced by two different routes. The first consists of altering the structure of the
urethane molecule basically by using polyols with certain properties such as:
•
high degree of aromaticity;
•
high molecular weight;
•
high functionality;
•
polyester instead of polyether based;
•
cyclic rather than open chain structure;
•
containing phosphorous, halogens, boron, sulphur and metal compounds.
The second method consists of using flame retardant additives such as the ones mentioned above. The
addition of these compounds has advantages, for their plasticizing properties help to make the
prepolymer components more compatible as well as the fact that it is much easier to use additives
than to develop new formulations as in the case of the first method.
The flame retardant used in this work is TCPP (tri-chloropropylphosphate).
Figure 2.18 Molecular structure of tric-chloropropylphosphate
2.4.7
Silicone surfactants
Almost all flexible polyurethane foams are made with the help of silicone based nonionic surfactants.
Surfactants lower the surface tension. They emulsify incompatible formulation ingredients, promote
the nucleation of bubbles during mixing, stabilize the rising foam by reducing stress concentrations in
10
thinning cell walls and counteract the defoaming effect of any solids added (such as fillers) or formed
(such as precipitated polyureas structures) during the foaming reaction. The stabilization of cell walls is
the most important of these functions. By doing this, the surfactant prevents the coalescence of
rapidly growing cells until those cells have attained sufficient strength through polymerization to
become self-supporting. Cell coalescence would otherwise lead to total foam collapse. Surfactants also
help to control the precise timing and the degree of cell opening (3).
Typically, one-component in the surfactant is hydrophobic (has affinity to the apolar phase) and
another is hydrophilic (has affinity to the polar phase).
The silicones used are surface active agents and can be classified in two groups depending on the type
of connection involved. If the connection is between the silicone Si and the O of polyether (Si-O-C) the
surfactant is hydrolysable, however if the connection is between the silicone Si and the C of polyether
(Si-C) it is not hydrolysable (3) (11).
11
3 Materials and methods
3.1 Reagents and additives
The reagents and additives employed in this work are listed in table 3.1
Table 3.1 Reagents and additives employed in this work
Type
Polyol
Crosslinker
Flame retarder
Silicone
Catalyst
Full name
Chemical name/specification
Functionality
GP1000
VD1000
Alfaster T401
FCA100
Cereclor S45
TCPP
B8871
DMDEE
DMDLS (high quality DMDEE)
Propylenoxide glycerol
Polypropylene glycol
3
2
1,62
2
2
-
Propane-1,2-diol
Chlorinated paraffin
Trichloropropylphosphate
Polysiloxane-polyether
2’-Dimorpholino diethyl ether
2’-Dimorpholino diethyl ether
70% bis (2-dimethylaminoethyl)
ether
Cell opener
Emulsifying agent
Rheology modifier
Methyl diphenyl diisocyanate
Dimethyl ether
Propane
Butane
Methyl propane
NIAX A1
Witco L6164
FCA 400
FCA 500
Suprasec 5025
DME
Propane
Butane
Isobutane
Additive
Isocyanate
Gases
-
3.2 Employed formulations
The composition of the formulations employed in this work is shown in Table 3.2 and Table 3.3.
Table 3.2 Formulations used in the repeatability trials
Average functionality of
compounds with OHv
Index excess NCO / OH
TCPP (pbw)
NIAX (pbw)
DMDEE (pbw)
DMDLS (pbw)
Silicone (pbw)
Gas weight as % of
(Polyol Blend + MDI)
DME (pbw)
IB (pbw)
1612 AWMB3
2631 AWB3
6396 GEMB3
2,46
2,39
2,11
4,3
40
0,2
1,2
0
8
4,3
40
0
1,3
0
8
4,8
25
0
0
1,45
3,5
33,17
19,72
23,46
22,4
17,9
12,8
10,2
50,06
40,96
12
Table 3.3 Formulations of the NIAX, DMDEE and Index series
“Mother”
formulation
compounds with OHv
TCPP (pbw)
NIAX (pbw)
DMDEE (pbw)
Silicone (pbw)
Gas weight as % of (Polyol
Blend + MDI)
DME (pbw)
IB (pbw)
compounds with OHv
TCPP (pbw)
NIAX (pbw)
DMDEE (pbw)
Silicone (pbw)
Gas weight as % of (Polyol
Blend + MDI)
DME (pbw)
IB (pbw)
DMDEE series
6459
GWMB3
6471
GWMB3
6472
GWMB3
6473
GWMB3
6474
GWMB3
6475
GWMB3
2,62
2,62
2,62
2,62
2,62
2,62
4,85
55
0,15
1,5
9,5
4,85
55
0,15
1,00
9,5
4,85
55
0,15
1,25
9,5
4,85
55
0,15
1,75
9,5
4,85
55
0,15
2,00
9,5
4,85
55
0,15
2,25
9,5
18,56
18,56
18,56
18,56
18,56
18,56
21,29
35,07
21,26
21,27
35,02
35,04
NIAX series
21,30
35,09
21,31
21,33
35,11
35,13
Index series
6465
GWMB3
6466
GWMB3
6467
GWMB3
6468
GWMB3
6481
GWMB3
6482
GWMB3
2,62
2,62
2,62
2,62
2,62
2,62
4,85
55
0
1,5
9,5
4,85
55
1
1,5
9,5
4,85
55
0,2
1,5
9,5
4,85
55
0,3
1,5
9,5
5,1
55
0,15
1,5
9,5
4,6
55
0,15
1,5
9,5
18,56
18,56
18,56
18,56
18,56
18,56
21,28
35,05
21,33
35,14
21,29
35,07
21,29
35,08
21,29
35,07
21,29
35,07
3.3 The AltaFoam Monitor
3.3.1
Overview
The AltaFoam Monitor is an apparatus composed of several moulds made of steel, with a grid that
opens to allow the placing of a covering paper, permitting also the access of humidity. This grid can
move back and forward, so that the mould gap is adjustable. The paper is cut to fit the mould,
including the areas of the curing, the pressure and the temperature sensors, which must not be
covered.
At one side, the AltaFoam Monitor is connected to the central software installed on a computer and
on the other side connected to the next mould in series. It has four measuring sensors: temperature,
height, pressure and curing and an environmental temperature and humidity sensor placed in an
exterior box and connected to the Monitor.
13
3.3.2
The temperature sensor and interpretation of temperature measurements
in the AFM
The AltaFoam Monitor uses a digital temperature sensor with an accuracy of ±2ºC in a temperature
range from -25ºC to 85ºC covered with an Erthalon tip.
Figure 3.1 Temperature sensor
Since the chemical reactions that occur in the foam are exothermal and the initial expansion of the
foam is due to the evaporation of liquid gas, the measurement of the temperature reveals a
temperature profile along the time (t=0 is when the bead is sprayed) as shown in Figure 3.2.
When the froth is dispensed, there is a temperature drop due to the gas escape. Then it rises to a
maximum associated to the exothermal polymerization reactions that can be more or less evident
depending on the reactivity of the froth and then it returns to room temperature.
Figure 3.2 Typical temperature profile measured with AltaFoam Monitor
Since the emulsification of the gases depends on the chemical characteristics of the blowing agents
used, the temperature profile can provide an indication of the kind and amount of gases used in the
system. This is given by the Average Linear Temperature drop rate (ALTdrop), as shown in equation 1:
14
𝐴𝐿𝑇𝑑𝑟𝑜𝑝 =
𝑇𝑠𝑡𝑎𝑟𝑡 − 𝑇𝑚𝑖𝑛
𝑡𝑇𝑠𝑡𝑎𝑟𝑡 − 𝑡𝑇𝑚𝑖𝑛
Equation 1
If one will take the Average Linear Temperature rise rate, starting on the minimum temperature, then
one can get an idea of the time it takes the temperature to get back to its original level because of the
exothermal chemical reactions and can indicate when these reactions have stopped:
𝐴𝐿𝑇𝑟𝑒𝑡𝑢𝑟𝑛 =
3.3.3
𝑇𝑟𝑒𝑡𝑢𝑟𝑛 − 𝑇𝑚𝑖𝑛
𝑡𝑇𝑟𝑒𝑡𝑢𝑟𝑛 − 𝑡𝑇𝑚𝑖𝑛
Equation 2
The distance sensor and interpretation of post-expansion measures in AFM
Figure 3.3 Distance sensor
At dispensing, the liquid prepolymer leaves the can and expands immediately to a low density froth,
due to the evaporation of the blowing agent. Once exposed to air the froth cures by reacting with the
moisture present in the air, which results in the formation of CO2 that consequently causes a second
expansion of the froth. The expansion of the froth due to the CO2 is called post-expansion and it is
calculated by the difference between the final and the initial height of the foam as a percentage of the
initial height, as showed in equation 3. The height of the foam is measured by a LED sensor that can
measure distances from 5 to 50 cm, with a resolution of less then 1.5 mm and an accuracy of ±8 mm.
𝑃𝐸𝑡𝑜𝑡 =
𝐻𝑚𝑎𝑥 − 𝐻0
𝐻0
Equation 3
The expansion of the foam after 10, 30 and 60 minutes is also calculated.
The rise of the froth while curing is also a very important detail depending on the main purpose of use
of a given formulation: high post-expansion is ideal for filling gaps, while lesser post-expansion is
required for filling door frames, for example.
15
3.3.4
The curing sensor and interpretation of curing measurements in AFM
The curing rate of the foam is evaluated by the measurement of the change of the dielectric properties
of the outer layer of the froth. Low-frequency dielectric measurements are applied to monitor the
evolution of the overall curing process of one-component polyurethane foams in a quantitative,
systematic and on-line fashion, without affecting the integrity of the final product.
Dielectric measurements provide a sensitive and convenient method to continuously monitor the
chemical processes responsible for the curing of polymeric products from froth to cross-linked solid.
An electric field is applied between two electrodes generating a double interaction of the polymeric
material: (a) polarization: alignment of dipoles with the electric field and (b) ionic conduction:
movement of electrically charged ions to the electrodes with opposite polarity. One of the intrinsic
properties of the curing polyurethane foam that shows distinct variations during the overall curing
process is the ion viscosity. Ion Viscosity, or electrical resistivity of the curing foam, is directly related
to the mobility of ions in the material. There is a direct link between ion viscosity and the ionic
conduction: an increase in ion viscosity obstructs the dipoles from being rearranged and impedes ions
from moving in the specimen, causing an electrical conductivity decrease. For most polymers, ion
viscosity follows closely the changes in mechanical viscosity and cure state and so it is measured
continuously throughout the curing process (13).
The sensor itself is a surface, or fringe, measurement sensor, comprised of two planar interdigitated
comb electrodes on an inert substrate. The electrode line width and the spacing between the
electrodes determines approximately how far into the material the fringe field will be measured.
The curing curve has three main parts, as shown in Figure 3.4:
Figure 3.4 Profile of the curing process measured with the AltaFoam Monitor
16
Part I represents the initial decrease in electric resistivity, where dipoles and charges move relatively
freely and it is the time when water starts to permeate the froth. When the minimum of electric
resistivity is reached, the second part of the curve begins, occurring an increase in electric resistivity
associated with the dipoles and charges moving less freely, which defines the process of curing, until it
reaches a maximum and the dipoles and charges do not move anymore. Here the process of curing is
over, which is translated visually as a stable line – part III. This sensor works by sending electric signals
to the material and reading the response. This means that this sensor can have a non-neglectible
influence in the curing process.
Since the measurement is dependant on the setup, a differential measurement is used: the time it
takes for the curing curve to reach 50% of its maximum value. This is called Creturn at tCreturn. When
tCreturn is 1 hour we say Alpha is 45 degrees. The higher the curing Alpha, the faster the foam cured at
the outer layer.
𝐴𝑙𝑝𝑕𝑎 (deg) = tan−1
𝐶𝑟𝑒𝑡𝑢𝑟𝑛 − 𝐶𝑚𝑖𝑛
𝑡𝐶𝑟𝑒𝑡𝑢𝑟𝑛 − 𝑡𝐶𝑚𝑖𝑛
∙
180
𝜋
Equation 4
Figure 3.5 Curing sensor
3.3.5
The pressure sensor and interpretation of pressure measurements in AFM
A good adhesion of the foam to the substrate is an important parameter and can be linked with the
pressure development of the foam. While curing and after the foam has cured the remaining force can
deform the substrate (door or window). Therefore it is desirable that the pressure is rising and falling
quickly and that the pressure remaining after curing is insignificant.
The maximum pressure and the time to get to 10% of this pressure are used as main indication about
this process. When the pressure of the foam is only slowly fading, the risk for problems with
dimensional stability and substrate deformation increases.
17
Figure 3.6 Pressure profile measured with AFM
The sensor employs a solid state piezoresistive pressure transducer with a pressure range from 0 to 30
psi and a dimethyl silicone diaphragm typ.
Figure 3.7 Pressure sensor
3.4 Variability in analytical measurements
Since the aim of this work is to study the repeatability of the AltaFoam Monitor equipment, it is
important to start by defining the concept of repeatability and its calculation procedure, which was
mostly based in (14).
All measurements are subject to measurement error. By error is meant the difference between the
observed value and the true value of the quantity being measured. Since true values are invariably
unknown, the exact magnitude of the error involved in an analytical result is also invariably unknown.
18
It is possible, however, to estimate the likely magnitude of such errors by careful study of the
properties of the analytical system. The term ‘analytical system’ refers to everything that impinges on
a measurement: the method, the equipment, the reagents, the analyst, the laboratory environments,
etc. It is fair to say that a measurement is of no value unless there is attached to it, either explicitly or
implicitly, some estimate of the probable error involved. When it comes to assessing the likely
magnitude of the analytical error in any test result, it is useful to distinguish between the types of
error that may occur. These are often described as systematic and random errors (15). Experimental
uncertainties that can be revealed by repeating the measurements are called random errors; those
that cannot be revealed in this way are called systematic (16). These lead to the situation where the
mean of any separate measurements differs significantly from the actual value of the measured
attribute. Sources of systematic error may be imperfect calibration of measurement instruments,
changes in the environment which interfere with the measurement process, among others. Random
error is always present in a measurement. It is caused by inherently unpredictable fluctuations in the
readings of a measurement apparatus or in the experimenter's interpretation of the instrumental
reading (17) (18).
Variation may be quantified in various ways. One of the simplest is to use the standard deviation as a
measure of precision: the larger the standard deviation, the worse the precision.
It is important always to distinguish between system parameters, such as the standard deviation, and
estimates of these parameters, calculated from the sample data. These latter quantities are called
‘sample statistics’ (any number calculated from the data is a ‘statistic’) and are themselves subject to
chance variation. System parameters, such as µ (average) and σ (standard deviation) are considered
fixed, though unknown, quantities. In practice, if the sample size n is very large, the result calculated
using equation 5 will often be labeled σ, since a very large set of measurements will give the ‘true’
standard deviation.
𝑠=
𝑛
𝑖=1
𝑥𝑖 − 𝑥
𝑛−1
2
Equation 5
If the sample size is small, the result is labeled s (or sometimes σ) as above; this makes clear to the
user that the calculated value is itself subject to measurement error, i.e. if the measurements were
repeated a different value would be found for the sample standard deviation.
A common requirement in analytical method validation is that the repeatability and either the
reproducibility or intermediate precision of the method be estimated. Repeatability and
reproducibility are descriptions of the precision of test results under different specifications of the
conditions under which measurements are made. Repeatability allows for as little variation as possible
in analytical conditions, whereas reproducibility allows for maximum variation in conditions, by
comparing results obtained in different laboratories, while still measuring the same analyte.
19
Measures of intermediate precision are similar to reproducibility in that the various factors which are
maintained constant for the definition of repeatability may be allowed to vary; the difference is that
all measurements are made in only one laboratory. The principal factors which may be varied are time,
operator, instrument and calibration. The determination of intermediate precision involves the
calculation of a term of variance associated with varying conditions within one laboratory. Different
measures of intermediate precision may be defined, depending on which combination of factors is
allowed to vary over the course of the validation study. These measures are usually obtained from
special validation studies, but they may also be estimated from control chart data. Since there aren’t
any validation studies about the AltaFoam Monitor or any control charts, these measures are outside
the scope of this work.
Repeatability conditions can be defined as “conditions where independent test results are obtained
with the same method on identical test items in the same laboratory by the same operator using the
same equipment within short intervals of time” (International Organization for Standardization). To
provide a quantitative measure of repeatability the ‘Repeatability Limit’ is defined as “the value less
than or equal to which the absolute difference between two test results obtained under repeatability
conditions may be expected to be with a probability of 95%”. On the assumption that under
repeatability conditions individual test results follow a Normal distribution with standard deviation σ,
the differences between pairs of such results will follow a Normal distribution with mean zero and
standard deviation
2𝜎𝑟2 , where σr is the repeatability standard deviation, ie, the standard deviation
of individual test results obtained under repeatability conditions. For all Normal distributions, 95% of
values lie within 1.96 standard deviations of the mean, so the magnitudes of differences (i.e., ignoring
the sign of the difference) between pairs of test results will be less than 1,96 2𝜎𝑟2 95% of the time.
Figure 3.8 Distribution of differences between two test results
Thus the repeatability limit is given by:
𝑅𝑒𝑝𝑒𝑎𝑡𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝐿𝑖𝑚𝑖𝑡 = 1,96 2𝜎𝑟2
20
Equation 6
Where σr is the repeatability standard deviation, i.e., the standard deviation of individual test results
obtained under repeatability conditions (15).
The repeatability standard deviation, sr, when applied to n samples is given by the following equation:
𝑠𝑟 =
𝑠12 + 𝑠22 + ⋯ + 𝑠𝑛2
𝑛
Equation 7
3.5 Quick tests
The Quick tests are made up of 3 main tests: froth/foam output testing, horizontal paper test and
horizontal mould test.
3.5.1
Froth/foam output testing
The purpose of this test is to determine the output rate of the foam in mass/time as well as the
percentage of gas lost into the atmosphere. It consists of dispensing the foam through the applicator
(gun or adapter) from the aerosol can during a certain time (t) which is usually 10 seconds. Two
different values are measured: the mass difference of the can before and after dispensing (released
liquid) and also the mass of foam dispensed (released foam). With these values three parameters are
calculated: output liquid, output foam and percentage of gas loss. This test is performed at a
can/curing temperature of 5/5ºC, which is the worst case scenario.
𝑂𝑢𝑡𝑝𝑢𝑡 𝑙𝑖𝑞𝑢𝑖𝑑 𝑔 𝑠 =
𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑 (𝑔)
𝑡 (𝑠)
Equation 8
𝑂𝑢𝑡𝑝𝑢𝑡 𝑓𝑜𝑎𝑚 𝑔 𝑠 =
𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑓𝑜𝑎𝑚 (𝑔)
𝑡 (𝑠)
Equation 9
𝐺𝑎𝑠 𝑙𝑜𝑠𝑠 % =
𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑 − 𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑓𝑜𝑎𝑚
𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑙𝑖𝑞𝑢𝑖𝑑
21
Equation 10
3.5.2
Horizontal paper test
This test consists of dispensing the foam horizontally on a piece of paper and leaving it to cure during
24 hours at constant ambient temperature. Various properties are observed and evaluated by giving a
rating from -5 to 5, being -5 the worst and 5 the best. On the following table a more detailed
description of the ratings are shown.
Table 3.4 Description of the foam properties rating syspem used in this work
Negative ratings
-5 ; -3
-3 ; -1
-1 ; +2
Very bad
Bad
Not acceptable
Positive ratings
+3 ; +4
+4 ; +5 (excluding)
+5
Acceptable
Good
Excellent
The test is applied at two different temperatures: 23/23ºC and 5/5ºC. The properties evaluated are
described as follows:
•
Shaking rate: it is observed before dispensing and consists of evaluating the difficulty in
shaking the can.
•
Froth outflow: after dispensing, froth outflow occurs when the bead flows to both of its sides,
decreasing in height. It is an important property because although low viscosity is desired
inside the can, after dispensing, the froth should be stable and give no outflow.
•
Froth shrinkage: almost immediately after dispensing, froth shrinkage occurs when there is a
decrease in froth size (height and width simultaneously).
•
Surface structure: here the foam can be evaluated as smooth or irregular. For example,
adapter applied froths give a smoother surface than gun applied froths.
•
Crumbling: Crumbling is associated to the presence of friable cells and is evaluated by
pressing down on the froth. If crumbling is present, a cracking sound is heard and in worse
cases the froth breaks away in small pieces (crumbs). This property is measured 1, 2 and 24
hours after dispensing the foam and is more notorious when curing takes place at lower
temperatures.
•
Glass Bubbles: Glass bubbles are identified by the shiny gloss of the froth surface. They are
more pronounced with gun applied foams and occur due to rapid evaporation of gas out of
the freshly extruded froth dissolving the cells at the surface.
•
Cell structure: This property considers the size and distribution of the cells in the foam. A
good froth should not have very large cells and they should be regularly distributed
throughout the sample.
•
Voids and Pin Holes: Voids and pin holes are created by liquid gas pockets in the prepolymer
mix before it is dispensed. These gas pockets occur due to bad solubility of the blowing agents
in the prepolymer and also due to poor shaking of the can prior to dispensing.
22
•
Base Holes: Base holes occur when the froth is dispensed on a porous or irregular surface.
Part of the blowing agent, usually DME, is captured in the substrate and is then released
slowly dissolving the freshly laid down foam in contact with the surface giving base holes. This
is a very important property due to the fact that the presence of base holes causes very poor
adhesion between the foam and the substrate.
•
Cell Collapse: Cell collapse is when the presence of large voids in the foam is detected usually
when the froth cures too slowly. The silicone surfactant looses its stabilisation power and the
cells collapse forming the large voids.
•
Curing Streaks: Curing streaks occur when it is possible to detect hard zones, usually in the
centre of the froth, made up of coarser cells. This is caused by curing difficulties of the froth.
3.5.3
Horizontal mould test
In this test the foam is dispensed horizontally in a wooden mould, illustrated in figure 3.9.
Figure 3.9 Schematic representation of a wooden mould used in horizontal mould tests
For adapter foams, approximately ½ of the mould’s compartment height is filled, while for gun foams
it’s ¾. These heights are estimated from experience that adapter foams expand more or less 100% and
gun foams expand 20%. Identically to the paper test, the horizontal mould test is applied at 23/23ºC
and at 5/5ºC. After 24 hours of curing, the foam is removed from the mould and the same properties
as in the paper test as well as a few more are evaluated. Only the properties that have not been
mentioned before will be explained next:
•
Mould release: as the foam bead is being released from the mould, it can be considered loose
or not loose.
•
Curing shrinkage: curing shrinkage occurs when the cured froth does not fill up the whole
volume of the compartment.
23
•
Side base holes: similar to base holes with the difference of being observed on the lateral part
of the foam bead.
•
Overall density in the mould: a portion of the bead released from the mould is used to
determine the density by water displacement.
24
4 Experimental results
4.1 Overview
This work studies the repeatability of the following variables measured by the AltaFoam Monitor:
post-expansion, angle of curing (alpha), minimum temperature, maximum temperature and maximum
developed pressure. Between each measurement the can is weighed and the liquid remaining inside
the can (%LIC) is calculated, according to equation 11. This gives an idea of where in the can the bead
belongs to. The percentage of liquid inside the can is the percentage value of the liquid remaining
inside the can (Wb) divided by the total amount of liquid inside the can before being used, that is, the
amount of chemicals from the formulation (W0):
%𝐿𝐼𝐶 =
𝑊𝑏
𝑊0
Equation 11
The method for calculation of the repeatability uses the difference between pairs of results. Since two
cans were used in each set of trials, this difference was calculated between results of each can in the
same order of decreasing %LIC. Whenever two cans don’t have the same number of beads, the
number of pairs of values used to calculate the difference corresponds to the number of beads of the
can with less beads, without any adjustment made to the standard deviation of the other can. In the
tables that present the results obtained R.L. represents the repeatability limit, a the number of values
of the difference between pairs of results that have to be smaller than the repeatability limit so that
the probability of it happening is 95%, b the number of values smaller than the repeatability limit, R
means that the variable is repeatable and NR means that the variable is non-repeatable.
It was also determined the coefficient of variation – CV, which is a normalized statistical measure of
the dispersion of data points in a data series around the mean. It is calculated as follows:
𝐶𝑉 =
𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛
𝑀𝑒𝑎𝑛
Equation 12
The coefficient of variation represents the ratio of the standard variation to the mean and it is a useful
statistic for comparing the degree of variation from one data series to another, even if the means are
extremely different from each other.
The advantage of the CV is that it is dimensionless, which allows it to be compared with each other in
ways that other measures, like standard deviation or root mean squared residuals cannot be.
25
4.2 Determination of outliers
Before proceeding with the determination of the repeatability of the measurements of the several
variables it is necessary to check the existence of outliers in those measurements, which could
adulterate the final results.
Outliers are atypical, infrequent observations - data points that do not appear to follow the
characteristic distribution of the rest of the data. They can reflect genuine properties of the underlying
phenomenon (variable), or be due to measurement errors or other anomalies which should not be
modeled. In this work they were detected graphically resorting to box and whisker plots of the data.
These plots place a box around the midpoint – in this case the median and the lower and upper values
st
rd
are the 1 and 3 quartiles and whiskers outside of the box which represent the non-outlier range.
A data point is considered to be an outlier if the following conditions hold:
•
Data point value > UBV + *o.c.*(UBV - LBV)
•
Data point value < LBV - *o.c.*(UBV - LBV)
Or
Where UBV is the upper value of the box in the box plot (e.g., the mean + standard error or the 75th
percentile), LBV is the lower value of the box in the box plot (e.g., the mean - standard error or the
25th percentile) and o.c. is the outlier coefficient equal to 1,5 (19).
Figure 4.1 Schematic representation of a box and whiskers plot
4.3 Sample size
Determining sample size is a very important issue because samples that are too large may waste time,
resources and money, while samples that are too small may lead to inaccurate results. In many cases,
it can be easy to determine the minimum sample size needed to estimate a process parameter, such
as the population mean, µ.
26
When sample data is collected and the sample mean 𝑥 is calculated, that sample mean is typically
different from the population mean µ. This difference between the sample and population means can
be thought of as an error. The margin of error E is the maximum difference between the observed
sample mean 𝑥 and the true value of the population mean µ:
𝐸 = 𝑧𝛼
Where 𝑧𝛼
2
𝜎
2
Equation 13
𝑛
is known as the critical value, the positive z value that is at the vertical boundary for the
area of 𝛼 2 in the right tail of the standard normal distribution; σ is the population standard deviation
and n is the sample size.
The rearrangement of the equation above allows solving for the sample size necessary to produce
results accurate to a specified confidence and margin of error.
𝑛=
𝑧𝛼
2
∙𝜎
2
Equation 14
𝐸
This formula can be used when the standard deviation of the population σ is known and we want to
determine the sample size necessary to establish, with a confidence of (1 – α), the mean value µ
within ±E (20).
Equation 14 shows that, for a certain degree of confidence, the sample size increases with increasing
standard deviation and decreases with increasing error. Hence for variables whose measurements
present a large standard deviation such as post-expansion and maximum developed pressure (see
tables in the following sections), one must not impose as much accuracy as for variables with little
variation, such as the curing angle. The sample size was thus determined for a degree of confidence of
90% and 95% and for values of error E as different percentages of the population average µ.
For a degree of confidence of 0,95 comes that α equals 0,05 and therefore 𝛼 2 equals 0,025,which
corresponds to a value of z equal to 1,96. Similarly, for a degree of confidence of 0,90 z equals 1,65 .
The tables with the sample size for the determination of each variable (post-expansion, alpha, etc)
with each set of formulation/conditions, where the conditions are the can/curing temperature and the
mould gap, are in Appendix 1.
To allow a clearer observation of the sample size required by the different formulations and respective
trial settings and its dependence on the error admitted for each variable, three surface plots were
made for post-expansion, alpha and maximum pressure, for a degree of confidence of 90%. In the
horizontal axis it is displayed the notation: (formulation; can/curing temperature; mould gap; aging),
which was used like this so not to clutter the chart.
27
Figure 4.2 Sample size for post-expansion as a function of the error
Figure 4.3 Sample size for alpha as a function of the error
28
Figure 4.4 Sample size for maximum pressure as a function of the error
Figures Figure 4.2Figure 4.3 andFigure 4.4 show how the sample size decreases contrarily to the error.
Furthermore, it shows that formulation 2631 at 23ºC/23ºC with 5 days of aging and a 3 cm mould gap
requires the largest samples when the smallest errors are imposed, which may be related to the fact
that this formulation and respective trial settings are not repeatable for these variables, as can be seen
in section 4.4.
4.4 Results of the repeatability trials
To assess the repeatability of the measurements in the AltaFoam Monitor several trials were made
using three different formulations: 1612 AWMB3, 2631 AWB3 and 6396 GEMB3, varying the mould
gap (2 cm and 3 cm) and the can/curing temperature (23ºC/23ºC and 5ºC/5ºC).
The experimental procedure of the repeatability tests consisted of filling 2 cans with the selected
formulation and 24 hours later putting the cans in the oven at 45ºC. After 1 or 5 days, the cans were
removed from the 45ºC oven and placed at the 23ºC room during at least 24 hours before spraying or
putting in the 5ºC room. For tests at this temperature, it was necessary to wait at least 8 hours before
spraying. The standard procedure for spraying in the AltaFoam Monitor can be found in Appendix 2.
The beads were afterward inspected for curing streaks, having been found in beads of formulation
1612 AWMB3 in the trial at 5ºC and in beads of formulation 2631 AWB3 with 5 days of aging, at
23ºC/23ºC in a 3 cm mould gap. The curing streaks found would be rated 3 according to the rating
system used in this work.
29
The results of the repeatability trials in adapter foam 1612 AWMB3 with 1 day of aging, at a can/curing
temperature of 23ºC with a 2 cm mould gap are shown in Table 4.1 as an example. The remaining
results are in Appendix 3.
Table 4.1 Results of the repeatability trials in adapter foam 1612 AWMB3: 1 day of aging; can/curing
temperature: 23ºC/23ºC; 2 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
420
100%
80
100%
18
100%
24
100%
5
95%
519
95%
83
95%
19
95%
25
95%
10
91%
186
91%
80
91%
20
91%
26
91%
9
86%
213
86%
83
86%
21
86%
25
86%
8
78%
377
82%
82
82%
20
82%
25
82%
12
73%
164
78%
80
78%
20
78%
25
78%
12
69%
229
73%
81
73%
20
73%
25
73%
14
66%
190
69%
84
69%
21
69%
26
69%
9
62%
233
66%
82
66%
20
66%
25
66%
17
58%
227
62%
81
62%
20
62%
24
62%
12
53%
217
58%
73
58%
20
58%
25
58%
18
48%
178
53%
73
53%
20
53%
25
53%
17
45%
409
48%
84
48%
18
48%
23
48%
9
41%
378
45%
79
45%
19
45%
23
45%
12
37%
258
41%
79
41%
20
41%
24
41%
16
34%
219
37%
84
37%
20
37%
24
37%
13
30%
238
34%
80
34%
19
34%
24
34%
20
25%
248
30%
78
30%
19
30%
24
30%
14
21%
219
25%
76
25%
19
25%
24
25%
19
18%
204
21%
84
21%
20
21%
25
21%
20
14%
187
18%
76
18%
19
18%
24
18%
21
14%
75
14%
19
14%
23
14%
23
Count
21
22
22
22
22
Average
262
80
19
24
14
StdDev
97
3
1
1
5
CV
Can 2
0,4
0,04
0,04
0,04
0,3
100%
249
100%
82
100%
19
100%
24
100%
8
96%
231
96%
81
96%
19
96%
24
96%
11
56%
270
56%
83
56%
18
56%
24
56%
6
53%
271
53%
84
53%
20
53%
24
53%
11
50%
119
50%
86
50%
21
50%
25
50%
8
48%
289
48%
80
48%
20
48%
25
48%
15
44%
216
44%
85
44%
20
44%
25
44%
17
42%
177
42%
81
42%
20
42%
25
42%
15
40%
183
40%
85
40%
22
40%
26
40%
16
37%
182
37%
84
37%
21
37%
25
37%
17
35%
161
35%
79
35%
20
35%
24
35%
18
32%
292
32%
74
32%
20
32%
25
32%
21
30
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
29%
192
20%
80
29%
19
29%
25
29%
19
20%
243
17%
80
20%
19
20%
23
20%
9
17%
210
13%
81
17%
19
17%
24
17%
19
13%
174
10%
76
13%
21
13%
24
13%
18
10%
202
10%
20
10%
24
10%
21
Count
17
16
17
17
17
Average
215
81
20
24
15
StdDev
49
3
1
1
5
CV
0,2
0,04
0,05
0,03
0,3
sr
77
3
1
1
5
R.L.
213
9
2
2
13
a
16
15
16
16
16
b
14
16
17
17
17
Repeatability
NR
R
R
R
R
Table 4.1 shows that the standard deviations for the measurements of post-expansion are very high
(respectively 37% and 23% of the average of each can) and differ very much between the two cans
(48%), which would cause one to promptly affirm that post-expansion is not a repeatable variable.
However, the method assumes that all test results are obtained under repeatability conditions, which
in the case of a curing foam are difficult to control and maintain. Indeed, let’s consider the example of
room temperature and humidity, both critical elements in the process of foam curing. Although lab
temperature and humidity were controlled they weren’t unvarying due to the entering and exiting of
people in the lab and improper functioning of air conditioning equipment and humidifiers. If the tests
are run during nighttime, it is expected that both these parameters are more steady, which will also
cause the results to differ from those obtained during the day.
The repeatability limit for the measurements of post-expansion is 213, which means that for the
measurements to be repeatable the differences between pairs of results would have to be smaller
than this value at least in 16 out of the 17 measurements of the trial, which does not happen, despite
it being a large number. For this reason, the post-expansion of formulation 1612 AWMB3 with one day
of aging, at a can and curing temperature of 23ºC and with a mould gap of 2 cm is non-repeatable.
As for minimum and maximum temperature, they have a more stable behavior than post-expansion,
which is confirmed by the standard deviation, which is the same for both cans and the coefficient of
variation, which is of an order of magnitude of centesimals. The measurements for Tmin and Tmax range
from 18ºC to 21ºC, and from 23ºC to 26ºC respectively, having thus an amplitude of 3ºC, which is
similar to the value of the accuracy of the temperature sensor (2ºC).
The average of the measurements of Tmin is 19ºC and 20ºC for can 1 and can 2, respectively, which is
much higher than the average of Tmin in the trials with the previous model of the AltaFoam Monitor –
around 12ºC, as can be seen in Appendix 4. This is due to the temperature sensor, which is a contact
sensor covered with an Ertalon (a type of extruded nylon, i.e. a polyamide) tip, while the previous
31
model used a non covered contact temperature sensor made of aluminum. A contact temperature
sensor has to make good thermal contact, which means that the sensor and the object or fluid are at,
or very close to, the same temperature. Aluminum has a thermal conductivity of 250 W/(m·K),
whereas nylon’s is one thousand times smaller. This means that the Ertalon tip causes an increase in
the response time, which compromises the accuracy of the test, given that the minimum temperature
occurs in the first minutes of the test due to the release of the blowing agents.
The maximum temperature has a small variation, like minimum temperature, yielding the same
average between the two cans, 24ºC, and a low standard deviation and coefficient of variation. This
value of the average is much closer, although smaller, to the value obtained with the aluminum
sensor, 26ºC. The increase in temperature is due to the exothermic foaming reactions and its
maximum takes more time to attain than the minimum.
Table 4.2 provides a broad perception of the repeatability results of the analyzed variables for the
different trials.
Table 4.2 Summary of the repeatability results of each trial for each analyzed variable
Trial
PEtot
Alpha
Pmax
Tmin
Tmax
1612AWMB3, 23ºC/23ºC, 2 cm, aging 1
2631AWB3, 23ºC/23ºC, 2 cm, aging 1
6396GEMB3, 23ºC/23ºC, 2 cm, aging 5
NR
R
R
R
NR
NR
NR
R
R
R
R
R
R
NR
R
R
R
R
R
NR
R
NR
R
NR
R
NR
NR
R
R
R
NR
NR
R
R
NR
R
R
R
R
R
Table 4.2 shows that there were no formulations that yielded repeatable results for every variable and
no pattern is visibly detectable that relates formulation type or test conditions to the repeatability of
the variables.
It is also worth notice that the only test performed at 5ºC shows repeatability for the three most
important variables: post-expansion, alpha and maximum pressure, despite curing streaks having been
found in its beads.
On the other hand, formulation 2631 AWB3 with 5 days of aging, at 23ºC and a 3 cm mould gap, in
which beads have also been found curing streaks, proved not to be repeatable for those same
variables.
Also part of the repeatability study is the analysis of the relations between variables for different
formulations and test conditions, which will be made in the following paragraphs.
The results of formulation 1612 with 5 days of aging, at can and curing temperature of 23ºC and in a 3
cm mould gap show repeatability for three extremely important parameters in foam curing: postexpansion, curing rate and maximum developed pressure and it can show how post-expansion evolves
throughout the can.
32
100%
80%
60%
40%
20%
%PEtot
450
400
350
300
250
200
150
100
50
0
0%
%LIC
Average
can 1
can 2
Figure 4.5 Post-expansion as a function of liquid in can
At dispensing (the second stage in the foaming process), liquid prepolymer leaves the can and starts to
expand to a low-density froth by vaporization of the blowing agent. Once exposed to the air (the third
stage of the foaming process), the froth cures by reaction with the moisture in there resulting in CO2
production that assures the post-expansion of the foam.
In Figure 4.5 is shown a clear decrease of post expansion toward the end of the can. This happens
because there is a decrease of the amount of gas that remains in the can as it is sprayed and that
causes the initial expansion of the froth. The post-expansion is thus dependent on froth density and
gas emulsification.
It was a purpose in the AFM construction that the curing of the froth was not dependent on the height
of the froth/foam bead. To investigate whether this happens or not, these two variables were plotted
against each other.
Figure 4.6 Curing angle alpha as a function of the initial height of the bead
Figure 4.6 displays, for formulation 1612 AWMB3 at 23ºC/23ºC, 5 days of aging and 3 cm mould gap, a
clear dependence of alpha with the initial bead height: the larger the latter is, the smaller the former
is. This tendency was detected for all trials that yielded repeatability for alpha and post-expansion,
since this is the most related to the initial height.
33
A possible explanation for this behavior is that as soon as the froth leaves the can, it begins to react
with the humidity in the air thus starting the curing process. If the initial height of a bead is below that
of the curing sensor, the time it takes for it to expand enough to reach it, although being less than one
minute, is not accounted by the curing sensor, creating the illusion that the froth cures more rapidly.
Table 4.3 Influence of initial bead height on Cstart and Cmin
1612AWMB3; aging 5; 3cm;
23ºC/23ºC
H0 (cm)
Cmin
(Gohm)
Cstart
(Gohm)
2631AWB3; aging 1; 2cm;
23ºC/23ºC
6396 GEMB3; aging 5; 3cm;
23ºC/23ºC
1,25
3,4
2,72
5,07
3,72
6,27
2,54
6,45
1,36
1,39
8,92
1,85
10,63
8,66
9,59
4,99
1,2
1,29
Table 4.3 shows a clear influence of H0 in Cstart and Cmin, in the way that a higher bead causes a
decrease in Cstart, given that by the time the foam reaches the curing sensor, water has already started
to permeate the froth and the subsequent reactions are already taking place, causing the dipoles and
charges to move less freely and thus causing an increase in Cmin.
In order to explore a possible relation between curing angle alpha and maximum developed pressure,
namely if a smaller curing angle means a higher developed pressure, these two variables were plotted
against each other for all trials that revealed simultaneous repeatability for both of them.
34
Table 4.4 Relation between curing angle Alpha and Pmax
Trial
Plot
Type of
behavior
1612/23ºC/2cm/aging1
A
B
C
D
35
Trial
Plot
Type of
behavior
A
Analyzing the plots in Table 4.4 one can observe the existence of four different relations between
alpha and Pmax. Indeed, type of behavior “A” shows an inverse relation between alpha and P max, such
as it was intended to prove: alpha decreases towards the end of the can while P max increases. This
behavior was verified in two trials: for formulation 1612 AWMB3 with 1 day of aging at 23ºC/23ºC
with a 2 cm mould gap and for formulation 6396 GEMB3 with 5 days of aging at 23ºC/23ºC in a 2 cm
mould gap.
The other three trials demonstrate each one a different behavior: “B” shows a direct relation between
the two variables, as both increase towards the end of the can; “C” shows no apparent relation
between the two variables and “D” shows a decrease of alpha towards the end of the can and a
decrease of Pmax towards the middle of the can followed by an increase in the final beads.
Although in the generality of the trials prevails a decrease in alpha and an increase in P max towards the
end of the can, these two tendencies only occur simultaneously in two trials, which doesn’t allow the
drawing of a conclusion.
The results of the repeatability trials in adapter foam 1612 AWMB3 with one day aging, at a can/curing
temperature of 5ºC and 2 cm mould gap indicate that there is repeatability for all variables except for
the temperature. It’s also noticeable that the minimum temperature doesn’t go much below the 5ºC
of curing temperature: 2ºC maximum, whereas for tests at 23ºC, the temperature inside the bead can
decrease 5ºC below room temperature (see Appendix 3).
Another evidence that can be detected by the AltaFoam Monitor is that post-expansion is greater at
5ºC than at 23ºC, due to increase viscosity of the froth, which is depicted in Figure 4.7, where the postexpansion of formulation 1612 with 1 day of aging in a 2 cm mould gap is plotted for the two
temperatures. Although there was no repeatability for the results of post-expansion of this
formulation with 1 day of aging at 23ºC, the data points are still below those of the test at 5ºC.
36
Figure 4.7 Post-expansion as a function of liquid in can for formulation 1612 AWMB3 with 1 day of
aging, in a 2 cm mould gap and a can/curing temperature of 23/23ºC and of 5/5ºC
Given that the curing angle alpha is repeatable for formulation 6396 GEMB3 in both 2 cm and 3 cm
trials, it makes sense to plot this parameter in these two different conditions.
Figure 4.8 Curing angle alpha of formulation 6396 as a function of liquid in can for 2 cm and 3 cm
mould gaps
Figure 4.8 shows that the thickness of the bead dispensed has a significant influence in the curing
speed (namely at the centre of the bead), and that the curing speed is higher in the mould with 2 cm
gap, which is expected since moisture reaches the centre of the bead more easily in a thinner bead.
As for post-expansion, there doesn’t seem to be any pattern, as Figure 4.9 shows.
37
Figure 4.9 Post-expansion of formulation 6396 as a function of liquid in can for 2 cm and 3 cm mould
gaps
It is known that gun applied foams have less post-expansion than adapter foams, because in the latter
case the humidity of the air can access the froth more easily through the adapter, whilst in the former
case humidity only enters when the gun opens. Figure 4.10 depicts it clearly.
Figure 4.10 Post-expansion as a function of %LIC for gun formulation 6396 GEMB3 and adapter
formulation 1612 AWMB3 with 5 days of aging, a can and curing temperature of 23ºC and a 3 cm
mould gap
4.5 Verification of the results of the previous study of the AFM
The previous study of the repeatability of the AltaFoam Monitor came to the conclusion that all
variables were repeatable for cans with 5 days in the 45ºC oven in a 2 cm mould gap with %LIC
between 40% and 60% (Appendix 4). In order to verify that illation the method used in the present
work for the determination of the repeatability was applied to the results of those tests.
38
Table 4.5 Results of the repeatability of beads with LIC between 40% and 60% of formulation 1612
AWMB3 with 5 days of aging in a 2 cm mould gap with the previous model of the AltaFoam Monitor
PEtot
Alpha
Tmin
Tmax
Pmax
sr
24
2
1
0,2
5
R.L.
47
4
2
0,5
11
a
14
14
14
14
14
b
14
13
12
14
14
Repeatability
R
NR
NR
R
R
As one can see in Table 4.5, there is no repeatability for curing angle alpha or for minimum
temperature.
To investigate if it would improve the repeatability, the method was applied to the results of the trials
of the present work for the beads with %LIC between 40% and 60%. The result is presented in Table
4.6.
Table 4.6 Repeatability results for beads with %LIC between 40% and 60%
Trial
PEtot
Alpha
Pmax
Tmin
Tmax
R
R
R
R
NR
NR
R
R
NR
NR
NR
R
NR
R
R
R
R
R
NR
NR
R
R
R
NR
R
R
NR
R
R
R
NR
NR
R
R
NR
R
R
R
R
R
In Table 4.6 the results in green represent improvements, the ones in orange mean that nothing has
changed and the ones in red have worsen. In general, most results have stayed the same, and the
same number of results has improved and worsen, in this case specially for alpha.
Therefore, it is fair to assume that the middle beads do not contribute to the repeatability of the
results more than the set of all the beads of a can.
4.6 Influence of chemical variables in the curing process
4.6.1
Overview
Each chemical constituent of a formulation plays an important role in its design and will give the foam
different attributes and properties, so it is interesting and important to test their influence with a
powerful tool like the AFM. For this purpose three chemical variables were tested: catalysts NIAX and
DMDEE and the index of excess NCO/OH. A series of formulations were designed, increasing or
39
decreasing the chemical variable in question, based on formulation 6459 GWMB3, which had returned
good results in paper and wooden mould analysis and was considered a very acceptable foam. The
procedure for these tests consisted of filling two cans with each formulation, putting it two days in the
45ºC oven and spraying 3 beads in the AFM in a 3 cm mould gap at 23ºC and 5ºC.
TablesTable 4.7 and Table 4.8 show the average results for each parameter.
of 23/23ºC
Mother
formulation
NIAX series
DMDEE
series
Index series
Formulation
NIAX
(pbw)
DMDEE
(pbw)
Index
PEtot
Alpha
Tmin
Tmax
Pmax
6459
0,15
1,5
4,85
41
72
21
25
17
6465
0
1,5
4,85
68
63
21
25
25
6467
0,2
1,5
4,85
57
60
21
24
24
6468
0,3
1,5
4,85
76
71
21
24
22
6466
1
1,5
4,85
47
60
22
25
31
6471
0,15
1
4,85
70
67
20
23
17
6472
0,15
1,25
4,85
56
68
21
24
14
6473
0,15
1,75
4,85
34
63
21
25
18
6474
0,15
2
4,85
43
72
20
24
20
6475
0,15
2,25
4,85
76
58
22
24
37
6481
0,15
1,5
4,6
95
25
22
25
33
6482
0,15
1,5
5,1
73
69
22
25
19
of 5/5ºC
Mother
formulation
NIAX series
DMDEE
series
Formulation
NIAX
(pbw)
DMDE
E
(pbw)
Index
PEtot
Alpha
Tmin
Tmax
Pmax
6459
0,15
1,50
4,85
64
59
6
9
27
6465
0,00
1,50
4,85
66
22
5
8
27
6467
0,20
1,50
4,85
88
42
6
9
31
6468
0,30
1,50
4,85
84
27
6
9
23
6466
1,00
1,50
4,85
81
-7
5
8
40
6471
0,15
1,00
4,85
75
32
6
10
29
6472
0,15
1,25
4,85
71
20
7
10
22
6473
0,15
1,75
4,85
81
16
7
9
15
6474
0,15
2,00
4,85
54
25
5
7
17
6475
0,15
2,25
4,85
47
22
5
8
17
40
4.6.2
Results of the NIAX series at 23/23ºC
Figure 4.11 NIAX series at 23/23ºC
The increase of the amount of catalyst, such as NIAX, causes an increase in the rate of the reactions,
which in turn increases the viscosity of the froth, and provides faster skin formation. Both higher
viscosity of the froth and faster skin formation difficult the CO2 escape. The humidity gets slower
through the skin and froth is curing slower and therefore more elastic to foam up under the pressure
increase by the CO2 development. Increasing post-expansion and pressure development can be
observed in Figure 4.11.
As for the other parameters, the curing angle doesn’t seem to be influenced by the variations in the
amount of NIAX, presenting oscillating values between 60º and 70º, and minimum and maximum
temperatures show a parabolic progress with increasing NIAX, although each having a range of only
1ºC.
41
It’s also worth mentioning that the base formulation, 6459, has the lowest post-expansion and
pressure development and highest curing angle.
Figure 4.12 Foam analysis of formulations of the NIAX series, in paper and in wooden mould, at
23/23ºC
Regarding the visual foam analysis in paper and in wooden mould, one notices significant variations in
the classification of base holes (BH) and side base holes (SBH) and minor variations in curing streaks.
These are in fact the major aspects of foam analysis that are influenced by catalysts. To minimize the
occurrence of base holes more catalyst is added because it increases the viscosity of the froth. As for
curing streaks, they are caused by curing difficulties of the froth. Given that NIAX causes a slower
curing within the froth, increasing its amount will cause the risk of curing streaks.
Figure 4.12 shows that, in general, base holes have a better classification in mould than in paper,
which can be explained because in mould the expanding froth develops a pressure against the mould
walls, breaking the base holes, whereas the paper surface may have irregularities, which capture the
gas, dissolving the fresh froth in contact with the substrate and causing base holes. Also generally BH
rating is better than SBH in the mould due to accumulation of DME in the corner of the mould, which
can also be seen in Figure 4.12.
According to the same figure, the pattern described in the first paragraph of this sub-section does not
seem to apply to the classification of base holes and side base holes because formulations with less
amount of NIAX have better ratings than formulations with a larger amount.
42
As for curing streaks, no formulation presented this problem except for the one with the most NIAX –
formulation 6466, which was rated 4,5 for curing streaks in mould.
The fact that the foam analysis doesn’t always yield the expected result may be indicative of the
complexity of the system in question (all the components of a formulation, curing conditions, curing
process) and the fallibility of the visual method of analysis.
Figure 4.13 Foam analysis of formulations of the NIAX series, in AFM mould, with a 3 cm mould gap, at
23/23ºC
Comparing the analysis of the AFM beads of the NIAX formulations with the analysis of the beads of
the same formulations sprayed in wooden mould, one can see that there are similarities: base holes in
mould, for instance, have analogous ratings, and none of the formulations presents curing streaks.
As for the dissimilarities between the two analyses, it is visible in Figure 4.13 that there is no variation
in the rating of side base holes, which correspond to the curing sensor area.
43
Figure 4.14 Overal mould density (wooden mould) of formulations of the NIAX series
Foam will have lower density when the amount of gas remaining in the cellular structure of the froth is
higher. There are three possible processes that can cause loss of gas and thus increase density:
-
When dispensing foam, gas that isn’t dissolved in the froth is lost.
-
Diffusion through cell membranes during the curing process.
-
Coalescence of cells when dispensing or during the curing process.
There are three chemical variables that increase density by affecting cell coalescence: catalyst,
plasticizer and index of excess NCO/OH. The higher is the amount of plasticizer, more cell membranes
are plasticized and weaker, causing cell collapse. Also the increase in catalyst amount gives rise to
faster skin formation, and consequent slower penetration of humidity and inside curing. This increases
the number of collapsed cells and consequently the density.
Figure 4.14 shows that all formulations have similar densities, except for formulation 6465, whose only
catalyst is DMDEE and is clearly denser. Since this goes against what has been said, it’s possible that
the density was not well determined for this formulation.
44
4.6.3
Results of the DMDEE series at 23/23ºC
Figure 4.15 DMDEE series at 23/23ºC
The influence of catalyst DMDEE on post-expansion was expected to be similar to the influence of
NIAX. However, in this case post-expansion shows a parabolic behavior with increase amount of
DMDEE.
On the other hand, the curing angle alpha still shows no influence of varying catalyst amount, falling
even in the same range of values as before.
45
Minimum temperature shows an increasing tendency, while maximum temperature appears to
progress according to an inverted parabola, increasing to a peak and decreasing again, which is
opposite to what happened in the NIAX series.
The increasing tendency of maximum pressure, explained for the previous case, is even clearer in
Figure 4.15.
Figure 4.16 Foam analyses of the formulations of the DMDEE series, in paper and in wooden mould, at
23/23ºC
As was said before, the increase of catalyst amount causes decrease in base holes and side base holes
and increase in curing streaks. In Figure 4.16 one can see the different ratings of base holes on paper:
increasingly worse from formulation 6475 to formulation 6472. Similarly for base holes in mould:
better rating for formulations 6474 e 6473 and worse for 6472. As for side base holes, however,
formulations 6472, 6473 and 6474 obtained a rating of 4 for this parameter, while the formulation
with most catalyst obtained a poorer rating: 3, oppositely to what was expected.
No formulation presented curing streaks.
46
Figure 4.17 Foam analysis of the formulations of the DMDEE series, in AFM mould, with a 3 cm mould
gap, at 23/23ºC
Figure 4.17 shows that the formulations present some variation in ratings for most parameters, such
as base holes, side base holes, voids and pin holes and cell collapse. Indeed, the ratings for base holes
show a positive influence of DMDEE in the improvement of this parameter, as we can see by the
consecutively worse ratings of the formulations with less amount of this catalyst: 6475 rates 4, 6474
and 6473 both rate 3,5 and 6472 rates 3. Formulation 6471, however, contradicts this sequence by
having the best rating, 5.
Once again, no curing streaks were found.
47
Figure 4.18 Overall density mould (wooden mould) for the formulations of the DMDEE series
Figure 4.18 shows an increase of 9,5% in overall mould density with increasing DMDEE, as it was
expected according to the explanation given before.
4.6.4
Results of the index of excess NCO:OH series at 23/23ºC
48
Figure 4.19 Index series at 23/23ºC
It is important to start by stating that three different formulations are not sufficient to obtain an
accurate determination of the dependence of the analyzed parameters with the index of excess
NCO:OH.
Higher values of index of excess NCO/OH result in a lower degree of prepolymerization of the
prepolymer and thus in lower froth viscosity. As has been said before, a less viscous froth leads to less
post-expansion and less pressure development. However, for more or less the same viscosity of the
froth, at different values of NCO:OH, post-expansion is expected to increase with increasing free NCO
because the amount of CO2 produced is higher.
Figure 4.19 shows an identical progress in post-expansion and pressure development: accentuated
decrease from formulation 6481 to formulation 6459 and a slight increase from this to formulation
6482.
Similarly to what happened in the analyses of the catalysts, the excess NCO:OH ratio causes a slower
inside curing of the froth, which would be expected to reflect in a decreasing curing angle. However,
the opposite takes place: the curing angle alpha is similar between formulations 6459 and 6482 and
much higher than formulation 6481.
49
Figure 4.20 Foam analysis of the formulations of the Index series in paper and in wooden mould at
23/23ºC
Shaking rate is strictly connected with the viscosity of the prepolymer inside the can. A less viscous
prepolymer gives a better shaking rate. The NCO:OH index has an influence in prepolymer size
distribution: the higher is NCO:OH, the smaller the size of the average prepolymer, decreasing the
viscosity of the froth and giving a better shaking rate. Figure 4.20 shows that formulation 6482, which
has an index of 5.1, obtained the highest rating, 5, whereas formulation 6481, which has an index
value of 4.6, obtained the lowest rating: -5.
The increase in NCO:OH index also increases base holes and glass bubbles, as it can be seen in Figure
4.20: formulation 6481 obtained a better rating than formulation 6482 for base holes and glass
bubbles, both in paper and in mould.
Given that an increase in the NCO:OH index causes a slower inside curing speed, it is expected that it
also causes curing streaks. However, neither formulation presents this problem.
50
Figure 4.21 Foam analysis of the formulations of the Index series in AFM mould, with a 3 cm mould
gap, at 23/23ºC
The analysis of the foam beads of the index formulations sprayed in the AFM mould shows similar
results to the analysis of the beads sprayed in the wooden mould, as one can see in Figure 4.21, where
formulation 6481 shows better ratings for base holes and side base holes and no curing streaks were
found in either formulation.
Figure 4.22 Overall mould density (wooden mould) for the formulations of the Index series
As was said in the sections above, both catalysts and NCO:OH ratio affect cell coalescence, increasing
the density of the foam. Therefore it was expected that formulation 6482 had a higher density than
formulation 6481, although Figure 4.22 shows the opposite.
51
4.6.5
Results of the NIAX series at 5/5ºC
Figure 4.23 NIAX series at 5/5ºC
In the tests at 5ºC (can and curing temperature), one can see that the post-expansion is generally
higher than at 23ºC due to increasing viscosity of the froth. Figure 4.23 shows that the same tendency
is verified for pressure development. As for the progress of these parameters, there continues to be an
increase with increasing amount of NIAX.
52
As for the curing angle alpha, it shows an evident decrease with increasing NIAX, which can be
explained by the slower inside curing caused by this catalyst together with the lower temperature,
which also causes a slower curing.
Figure 4.24 Foam analysis of the formulations of the NIAX series, in paper and in wooden mould, at
5/5ºC
The foam analysis of the NIAX formulations at 5ºC doesn’t show very clear results, given that it was
expected that formulations with higher content of catalyst had better ratings in base holes and side
base holes than formulations with less amount. This is only evident for base holes in mould, where
formulation 6466 was rated 5, formulations 6468 and 6467 were rated 4 and formulation 6465 was
rated 3,5.
As for curing streaks in mould, the formulation with highest content of NIAX, 6466, was the only to be
rated 4, while the others were rated 5 and therefore did not have this problem.
Another evidence to be drawn from Figure 4.24 is the bad ratings for shaking rate, which is a problem
at lower temperatures due to the increase of viscosity of the prepolymer. However, if catalysts
increase viscosity, it was expected that formulation 6466 had the worse rating, but instead it’s
formulation 6468. Since this result is contradictory, it is possible that it wasn’t properly rated, given
that it’s hard to distinguish between such low ratings of shaking rate.
53
Figure 4.25 Foam analysis of formulations of the NIAX series, in AFM mould, at 5/5ºC
The foam analysis of the NIAX formulations in the AFM mould at 5ºC displays results that are very
similar to the results in wooden mould which, despite not showing agreement with theory, at least
seems to imply some equivalence between both moulds.
Figure 4.26 Output liquid for formulations of the NIAX series
The froth/foam output depends on viscosity. If a froth is too viscous, it will have a lower output. Hence
it is expected to decrease with increasing amount of NIAX.
54
Figure 4.26 shows that formulation 6465, with 0 pbw NIAX, has indeed the highest output. However,
there is an abrupt decrease from formulation 6465 to formulation 6467, which has the smallest nonzero amount of NIAX of the series and a gradual increase from this formulation to the next ones.
4.6.6
Results of the DMDEE series at 5/5ºC
Figure 4.27 DMDEE series at 5/5ºC
55
Figure 4.27 shows that the progress of post-expansion, curing angle alpha and pressure development
of the DMDEE series at 5ºC differs very much from the trials at 23ºC.
Indeed, post-expansion presents much higher values, as expected at a lower temperature, but instead
of increasing with increasing catalyst amount, it decreases. The same happens with maximum
pressure.
The average values of alpha also decrease, due to the lower temperature, which causes a slower
curing, but without any visible pattern likely to be related with DMDEE variation.
Figure 4.28 Foam analysis of the formulations of the DMDEE series, in paper and in wooden mould, at
5/5ºC
The analysis of the DMDEE formulations at 5ºC is analogous to the analysis made for the NIAX series:
although there is variation in the ratings, the results aren’t clear.
56
Figure 4.29 Foam analysis of the formulations of the DMDEE series, in AFM mould, at 5/5ºC
The foam analysis of the DMDEE formulations in the AFM mould at 5ºC displays results that are very
similar to the results in wooden mould, which seems to imply some equivalence between both
moulds, although the ratings don’t allow any conclusion to be drawn as far as the influence of DMDEE
amount variation in the foams is concerned.
Figure 4.30 Output liquid for the formulations of the DMDEE series
The output rate is expected to decrease with increasing catalyst amount. However, Figure 4.30 shows
an increase.
57
4.6.7
Results of the index of excess NCO:OH series at 5/5ºC
No trials were made in AFM at 5/5ºC for the index series. This section presents only the results of the
quick tests made for the referred formulations in paper and in wooden mould.
Figure 4.31 Foam analysis of the formulations of the Index series, in paper and in wooden mould, at
5/5ºC
The foam analysis of the index formulations at 5/5ºC indicate a decrease in shaking rate of formulation
6481, characteristic of a low temperature, but still with a rate above that of formulation 6482.
As for base holes and glass bubbles, it can be seen in Figure 4.31 that ratings have worsened but
formulation 6481 still obtained a better rating than formulation 6482, both in paper and in mould.
Figure 4.31 also evidences the appearance of slight curing streaks in mould of formulation 6481.
58
Figure 4.32 Output liquid for the formulations of the Index series
The NCO:OH ratio lowers froth viscosity, hence increasing output rate. Figure 4.32 illustrates this
effect, since formulation 6481 had an output of approximately 3 g/s which is even non-acceptable for
a commercial formulation (>4.5 g/s), and formulation 6482 had an output of 9 g/s.
59
5 Future developments
The curing process of a one-component polyurethane foam is a very complex system, that involves
many input (amount and type of chemicals in the formulations, temperature, humidity, mould gap
size,…) as well as response variables (post-expansion, curing rate, developed pressure,…) and
therefore it is called a multivariate system.
It would be both interesting and useful to study the relationship between all these variables, using the
results that AltaFoam Monitor provides, in the light of multivariate approaches, especially for pattern
recognition and using multivariate chemometric techniques chemometrics, such as Principal
Components Analysis (PCA), to help interpret the data.
Figure 5.1 Representation the three principal components of a PCA analysis of formulations 1612
AWMB3, 2631 AWB3 and 6396 GEMB3
Figure 5.1 shows the representation of the three principal components of a PCA analysis of
formulations 1612 AWMB3, 2631 AWB3 and 6396 GEMB3. The fact that the results for each
formulation appear grouped is revealing that there are patterns that can differentiate them, wich
shows how powerful these techniques can be.
60
6 Conclusions
The repeatability trials carried out with three different formulations (1612 AWMB3, 2631 AWB3, 6396
GEMB3) submitted to two different aging periods (1 and 5 days), at two different can/curing
temperatures (23ºC/23ºC and 5ºC/5ºC) in two mould gap sizes (2 and 3 cm) in order to determinate
the repeatability of the AltaFoam Monitor, resorting to a statistical method, towards variables as postexpansion, curing angle alpha, maximum developed pressure and minimum and maximum
temperatures revealed that there is not a pattern for the repeatability of said variables, formulations
or trial settings. Indeed, repeatability was obtained in all trials for some of the analyzed variables, but
not all of them. In the same way, there was not found a specific condition, like formulation used, aging
of the can, mould gap size or can/curing temperature that ensures repeatability for a certain variable.
Some known relations between the analyzed variables can be verified in the AltaFoam Monitor, such
as post-expansion being larger at lower temperatures and for adapter applicators (compared to gun
applicators) and curing rate (alpha) being larger for thinner beads.
It was observed that curing angle alpha is influenced by the initial height of the sprayed bead (H 0): the
smaller the bead, the larger the angle. Furthermore, it was discovered that the initial measure of ion
viscosity, Cstart, decreases with increasing H0, whereas Cmin increases, creating the illusion of a faster
curing.
The establishment of a relation between curing angle and maximum developed pressure proved
inconclusive, for there were four different behaviors involving the two variables.
A previous study made on the repeatability of AltaFoam Monitor concluded that there was
repeatability for all variables in tests performed in cans matured 5 days at 45ºC, in a 2 cm mould gap
for beads with liquid in can between 40% and 60%. To verify these results, the statistic method
employed in this work was applied to the data from that previous study and revealed that alpha and
minimum temperature were not repeatable. The method was also applied again to the data from the
present work, but for beads with liquid in can between 40% and 60% and it did not improve the
repeatability results.
The study of the influence of chemical variables focused on catalysts NIAX and DMDEE and the index
of excess NCO:OH, demonstrating that those influence post-expansion and developed pressure, but
not so much curing angle and temperature. As for index of excess NCO:OH, only three formulations
were compared and the results are not conclusive.
The quick tests performed on these formulations showed similar results between the wooden mould
and the AFM steel mould, as well as the very few curing streaks, especially in the beads from the AFM
mould.
61
7 Bibliography
1. Buist, J. M. Advances in Polyurethane Technology. India : John Wiley & Sons, 1968.
2.
Vilar,
Walter
Dias.
Chemistry
and
Technology
of
Polyurethanes.
[Online]
2002.
http://www.poliuretanos.com.br.
3. Lee, Shau-Tarnq e Ramesh, N. S., [ed.]. Polymeric Foams: Mechanisms and Materials (Polymeric
Foam Series). Boca Raton : CRC, 2004.
4. Mark, Herman F. Encyclopedia of Polymer Science and Technology. New York : Wiley-Interscience,
2004. Vol. 4.
5. Stevens, Malcolm P. Polymer Chemistry: An Introduction. New York : Oxford University Press, USA,
1998.
6. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim : Wiley-VCH, 2003.
7. Schrijver, A. ONE COMPONENT POLYURETHANE FOAM - Correlations between control and response
variables. 2003.
8. Aneja, Ashish. Structure-Property Relationships of Flexible Polyurethane Foams. Virginia Polytechnic
Institute and State University. Blacksburg, Virginia : s.n., 2002. Dissertation.
9. Thomson, Timothy. Polyurethanes as Specialty Chemicals: Principles and Applications. Boca Raton :
CRC, 2004.
10. Vis, S. Altachem Polyurethane Raw Materials. [ppt document] 2009.
11. Schrijver, A. Development guidelines on speciality PU foams in aerosol cans. 2001. Internal Report.
st
12. Understanding Chain Extenders and Crosslinkers. s.l. : SpecialChem, July 21
2004.
http://www.specialchem4polymers.com.
13. Vandenbossche, Lode, Dupré, Luc e Melkebeek, Jan. On-line cure monitoring of polyurethane
foams by dielectric viscosity measurements, IOS Press, 2007, International Journal of Applied
Electromagnetics and Mechanics, Vol. 25.
14. Mullins, E. Statistics for the Quality Control Chemistry Laboratory. London : Royal Society of
Chemistry, 2003.
15. Skelton, Bob. Process Safety Analysis: An Introduction. New York : Institute of Chemical Engineers,
1997.
16. Taylor, John R. An Introduction to Error Analysis: The Study of Uncertainties in Physical
Measurements. Sausalito, CA : University Science Books, 1996.
17. Systematic error. Wikipedia. [Online] http://en.wikipedia.org/wiki/Systematic_error, consulted in
October 2009.
18. Random error. Wikipedia. [Online] http://en.wikipedia.org/wiki/Random_error, consulted in
October 2009.
19. [Online] Statsoft. http://www.statsoft.com, consulted in October 2009.
20.
How
To
Determine
Sample
Size,
Determining
Sample
Size.
iSixSigma.
http://www.isixsigma.com/library/content/c000709a.asp, consulted in October 2009.
62
[Online]
21. Simão, Cláudia. The AltaFoam Monitor in R&D of One Component Polyurethane Foams, Academic
Training in Chemistry. 2006.
63
8 Appendix
Appendix 1.
Sample size for the calculation of AFM curing variables
Post-expansion
Form
.
Can/
curing
temp.
(ºC)
Mould
gap
size
(cm)
2
Aging
(days)
1
Error as % of average
µ
241
σ
82
n
23/23
1612
3
5/5
2
5
1
1
250
348
137
78
n
104
n
32
n
2
2631
23/23
5
3
2
6396
5
5
140
137
53
44
n
76
n
13
n
23/23
3
5
60
15
n
64
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
15%
20%
25%
30%
35%
36
48
60
72
84
14
8
5
4
3
20
12
8
5
4
37
50
62
75
87
12
7
5
3
3
17
10
7
5
4
52
70
87
104
122
11
7
4
3
2
16
9
6
4
3
21
27
34
41
48
7
4
3
2
2
10
6
4
3
2
21
28
35
42
49
13
7
5
4
3
18
10
7
5
4
21
27
34
41
48
38
21
14
10
7
53
30
20
14
10
8
11
13
16
18
8
5
3
2
2
11
6
4
3
2
9
12
15
18
21
8
5
3
2
2
11
6
4
3
2
Curing angle alpha
Form
.
Can/
curing
temp.
(ºC)
Mould
gap
size
(cm)
2
Aging
(days)
1
µ
81
σ
3
n
23/23
1612
3
5/5
2
5
1
1
72
71
65
7
n
7
n
4
n
2
2631
23/23
5
3
2
6396
5
5
67
46
83
3
n
6
n
2
n
23/23
3
5
74
6
n
65
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
2,5%
5%
10%
15%
20%
2
4
8
12
16
8
2
1
1
1
12
3
1
1
1
2
4
7
11
14
37
10
3
2
1
53
14
4
2
1
2
4
7
11
14
44
11
3
2
1
63
16
4
2
1
2
3
7
10
13
17
5
2
1
1
24
6
2
1
1
2
3
7
10
13
7
2
1
1
1
9
3
1
1
1
1
2
5
7
9
82
21
6
3
2
116
29
8
4
2
8
11
13
16
18
8
5
3
2
2
11
6
4
3
2
9
12
15
18
21
8
5
3
2
2
11
6
4
3
2
Maximum pressure
Form
.
Can/
curing
temp.
(ºC)
Mould
gap
size
(cm)
2
Aging
(days)
1
µ
14
σ
5
n
23/23
1612
3
5/5
2
5
1
1
11
1,0
9
5
n
0,7
n
6
n
2
2631
23/23
5
3
2
6396
5
5
0,8
6
6
0,4
n
4
n
2
n
23/23
3
5
8
3
n
66
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
E
1-α =
90%
1-α =
95%
15%
20%
25%
30%
35%
2
3
4
4
5
14
8
5
4
3
20
11
7
5
4
2
2
3
3
4
24
14
9
6
5
34
19
13
9
7
0,1
0,2
0,2
0,3
0,3
64
36
23
16
12
90
51
33
23
17
1
2
2
3
3
51
29
19
13
10
72
41
26
18
14
0,1
0,2
0,2
0,2
0,3
32
18
12
8
6
46
26
17
12
9
1
1
2
2
2
60
34
22
15
11
85
48
31
22
16
1
1
2
2
2
12
7
5
3
3
17
10
6
5
3
1
2
2
2
3
15
9
6
4
3
21
12
8
6
4
Appendix 2.
Standard procedure for spraying in AltaFoam Monitor
Preparation of the mould

Duct-tape curing sensor in perfect conditions and closely attached to the sensor

Prepare the paper cover with the holes for the curing, for the temperature and for the pressure
sensors

Put parafilm in the pressure sensor zone in the paper cover

Put the paper cover with parafilm in the pressure sensor area in place, as close to the mould as
possible, so as not to interfere with the height sensor

Hold the grid in place with pins
Measurement

Start the Altachem Foam Monitor software:

Click Start Test menu on the top of the screen

Select the available mould

In the next dialog box insert all the settings for the measurement, then click the Save button

The formulation number will appear in the name of the ALT file, so it can be used to identify it

Press Start Testing

Wait 3 minutes before spraying the bead into the AFM mould or until the height and pressure
sensors are at zero level and the temperature level indicates the room temperature

When spraying, make sure to cover the curing sensor completely, which corresponds to a height
of 4 cm

Weigh can after spraying

Determine %LIC between measurements in the end of the measurement
Interpretation

Discard measurements if beads higher than 11 cm

After the measurement is over, observe the cured bead and discard the measurement if any of
the following is true:


Big voids near the temperature sensor

Curing streaks (or cell collapse in worst cases) near the sensors
Check also for base holes near curing sensor
67
Appendix 3.
Results of the repeatability trials
1612 AWMB3. 5 days aging; can/curing temperature: 23ºC/23ºC; 3 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
301
100%
59
100%
18
100%
24
100%
10
93%
343
93%
67
93%
19
93%
25
93%
6
88%
394
88%
75
88%
19
88%
24
88%
8
84%
301
84%
67
84%
19
84%
23
84%
9
79%
257
79%
71
79%
19
79%
23
79%
12
75%
243
75%
80
75%
19
75%
23
75%
15
60%
343
60%
80
60%
19
60%
23
60%
14
56%
307
56%
79
56%
19
56%
24
56%
14
53%
308
53%
77
53%
19
53%
24
53%
17
49%
193
49%
83
49%
19
49%
24
49%
11
45%
310
45%
81
45%
20
45%
25
45%
14
41%
328
41%
75
41%
18
41%
24
41%
12
35%
226
35%
77
35%
19
35%
23
35%
4
28%
329
28%
79
28%
20
28%
24
28%
14
24%
192
24%
69
24%
19
24%
24
24%
15
20%
104
20%
84
20%
20
20%
25
17%
86
17%
69
17%
20
17%
24
Count
17
17
17
17
15
Average
269
75
19
24
12
StdDev
85
7
1
1
4
CV
0,3
0,09
0,03
0,03
0,3
Can 2
100%
144
100%
61
100%
21
100%
23
100%
5
98%
262
98%
61
98%
18
98%
24
98%
3
90%
368
90%
66
90%
18
90%
24
90%
4
84%
233
84%
78
84%
17
84%
23
84%
4
80%
290
80%
69
80%
18
80%
24
80%
7
76%
212
76%
72
76%
19
76%
25
76%
6
71%
328
71%
80
71%
20
71%
24
71%
5
68%
250
68%
77
68%
19
68%
24
68%
14
64%
249
64%
72
64%
19
64%
24
64%
14
60%
301
60%
71
60%
19
60%
25
60%
8
57%
280
57%
69
57%
20
57%
25
57%
16
53%
205
53%
64
53%
18
53%
24
53%
7
48%
121
48%
74
48%
19
48%
23
48%
9
45%
246
45%
74
45%
19
45%
24
45%
16
40%
259
40%
66
40%
19
40%
24
40%
20
36%
227
36%
71
36%
17
36%
23
36%
12
31%
130
31%
67
31%
18
31%
24
31%
21
27%
107
27%
66
27%
21
27%
25
27%
18
23%
218
23%
64
23%
19
23%
24
23%
20
68
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
Count
19
19
19
19
19
Average
233
70
19
24
11
StdDev
70
5
1
1
6
CV
0,3
0,08
0,05
0,03
0,5
sr
78
6
1
1
5
R.L.
216
17
2
2
14
a
16
16
16
16
14
b
17
17
15
16
15
Repeatability
R
R
NR
R
R
1612 AWMB3: 1 day aging; can/curing temperature: 5ºC; 2 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
267
100%
65
100%
5
100%
10
100%
1
83%
388
93%
76
93%
4
93%
9
93%
0
77%
484
87%
76
87%
5
87%
9
87%
2
73%
353
83%
77
83%
5
83%
10
83%
2
70%
415
77%
79
77%
5
77%
9
77%
2
65%
239
73%
78
73%
5
73%
9
73%
0
52%
490
70%
72
70%
6
70%
9
70%
1
47%
315
65%
75
65%
7
65%
8
65%
2
43%
327
52%
79
52%
6
52%
12
52%
1
38%
229
47%
80
43%
6
47%
13
47%
1
32%
286
43%
78
38%
7
43%
12
43%
1
29%
202
38%
69
32%
7
38%
12
38%
1
26%
414
32%
80
29%
7
32%
13
32%
2
21%
396
29%
76
26%
4
29%
11
29%
2
15%
110
26%
70
21%
3
26%
8
26%
0
21%
62
15%
5
21%
7
21%
0
15%
47
15%
8
15%
2
Count
15
17
16
17
17
Average
328
73
5
10
1
StdDev
107
8
1
2
1
CV
0,3
0,1
0,2
0,2
0,7
Can 2
100%
262
100%
70
100%
4
100%
9
100%
1
95%
382
95%
65
95%
3
95%
7
95%
0
88%
307
88%
73
88%
4
88%
8
88%
0
82%
326
82%
75
82%
4
82%
8
82%
1
78%
325
78%
67
78%
5
78%
8
78%
1
59%
435
63%
71
63%
3
63%
7
63%
1
54%
406
59%
70
59%
3
59%
8
59%
0
47%
420
54%
60
54%
4
54%
8
54%
0
42%
463
47%
65
47%
4
47%
8
47%
1
37%
598
42%
69
42%
4
42%
9
42%
1
69
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
32%
293
37%
73
37%
3
37%
8
37%
0
22%
263
32%
69
32%
4
32%
8
32%
1
22%
66
22%
5
22%
8
22%
1
Count
12
13
13
13
13
Average
373
69
4
8
1
StdDev
98
4
1
0,5
0,4
CV
0,3
0,06
0,2
0,06
0,6
sr
103
7
1
1
1
R.L.
285
18
3
3
2
a
11
12
12
12
12
b
11
13
9
8
12
Repeatability
R
R
NR
NR
R
2631 AWB3. 1 day of aging; can/curing temperature: 23ºC/23ºC; 2 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
107
100%
72
100%
20
100%
24
100%
15
96%
118
96%
67
96%
21
96%
24
96%
11
91%
111
91%
68
91%
21
91%
24
91%
17
86%
146
86%
67
86%
19
86%
23
86%
11
80%
138
80%
65
80%
20
80%
23
80%
17
76%
126
76%
68
76%
21
76%
24
76%
8
70%
100
70%
70
70%
20
70%
24
70%
14
65%
135
65%
67
65%
20
65%
23
65%
18
60%
112
60%
65
60%
21
60%
24
60%
14
55%
123
55%
64
55%
20
55%
24
55%
12
50%
110
50%
64
50%
21
50%
25
45%
11
39%
111
45%
61
45%
19
45%
23
39%
17
29%
199
39%
61
39%
20
39%
23
35%
10
23%
148
35%
61
35%
21
35%
24
29%
16
29%
63
29%
20
29%
24
23%
13
23%
61
23%
20
23%
23
18%
13
18%
56
18%
20
18%
24
Count
14
17
17
17
16
Average
127
64
20
24
14
StdDev
26
4
1
0,5
3
CV
0,2
0,06
0,03
0,02
0,2
Can 2
100%
190
100%
65
100%
20
100%
24
100%
4
94%
172
94%
70
94%
22
94%
25
94%
3
89%
147
89%
67
89%
21
89%
24
89%
3
84%
166
84%
68
84%
21
84%
24
84%
3
79%
134
79%
64
79%
20
79%
24
79%
3
74%
171
74%
70
74%
19
74%
23
74%
2
70
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
69%
125
69%
69
69%
20
69%
24
69%
2
64%
178
64%
70
64%
21
64%
25
64%
2
59%
96
59%
71
59%
21
59%
24
59%
3
54%
135
54%
69
54%
20
54%
24
54%
4
48%
149
48%
68
48%
20
48%
24
48%
2
41%
104
41%
60
41%
19
41%
23
41%
3
35%
226
35%
62
35%
20
35%
24
35%
5
30%
136
30%
59
30%
21
30%
25
30%
5
25%
120
25%
61
25%
21
25%
24
25%
6
19%
124
19%
64
19%
20
19%
24
19%
6
13%
103
13%
20
13%
24
Count
17
16
17
17
16
Average
146
66
20
24
4
StdDev
35
4
1
0,4
1
CV
0,2
0,06
0,03
0,02
0,4
sr
30
4
1
0,5
2
R.L.
84
11
2
1
16
a
13
15
16
16
15
b
14
16
17
17
1
Repeatability
R
R
R
R
NR
2631 AWB3. 5 days of aging; can/curing temperature: 23ºC/23ºC; 2 cm mould gap
Can 1
Count
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
114
100%
70
100%
20
100%
24
100%
1
95%
148
95%
64
95%
20
95%
24
95%
2
91%
139
91%
63
91%
20
91%
24
91%
0
85%
113
85%
68
85%
21
85%
25
85%
1
80%
183
80%
68
80%
21
80%
24
80%
1
76%
133
76%
70
76%
20
76%
23
76%
0
72%
233
72%
67
72%
21
72%
24
72%
1
66%
66
66%
64
66%
20
66%
24
66%
1
62%
90
62%
68
62%
19
62%
24
62%
1
57%
133
57%
68
57%
20
57%
24
57%
0
53%
229
53%
65
53%
22
53%
25
53%
0
48%
145
48%
69
48%
21
48%
25
48%
0
43%
91
43%
67
43%
20
43%
23
43%
1
38%
136
38%
66
38%
20
38%
23
38%
1
33%
92
33%
66
33%
21
33%
24
33%
0
28%
181
28%
67
28%
21
28%
24
28%
0
23%
123
23%
66
23%
20
23%
24
23%
2
17%
170
17%
63
17%
20
17%
24
17%
1
11%
71
11%
61
11%
20
11%
25
19
19
19
71
19
18
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
Average
136
66
20
24
1
StdDev
47
2
1
1
0,4
CV
0,3
0,04
0,03
0,02
0,6
Can 2
100%
144
100%
71
100%
21
100%
25
100%
1
96%
151
96%
69
96%
20
96%
24
96%
1
90%
122
90%
68
90%
20
90%
23
90%
1
85%
183
85%
68
85%
20
85%
24
85%
1
80%
110
80%
71
80%
19
80%
24
80%
1
77%
195
77%
71
77%
20
77%
24
77%
1
74%
106
74%
68
74%
21
74%
25
74%
1
71%
196
71%
70
71%
21
71%
24
71%
0
66%
97
66%
71
66%
19
66%
23
66%
1
61%
233
61%
69
61%
20
61%
24
61%
1
56%
125
56%
67
56%
21
56%
24
56%
0
46%
139
46%
71
46%
20
46%
24
46%
1
39%
195
39%
69
39%
20
39%
24
39%
1
34%
108
34%
68
34%
20
34%
24
34%
1
29%
60
29%
66
29%
21
29%
24
26%
1
26%
116
26%
65
26%
21
26%
25
12%
2
21%
144
21%
63
21%
20
21%
24
17%
159
17%
66
17%
20
17%
23
12%
146
12%
19
12%
23
Count
19
18
19
19
16
Average
144
68
20
24
1
StdDev
42
2
1
1
0,4
CV
0,3
0,03
0,03
0,03
0,4
sr
45
2
1
1
0,4
R.L.
124
7
2
2
1
a
18
17
18
18
15
b
17
18
19
19
15
Repeatability
NR
R
R
R
R
2631 AWB3: 5 days of aging; can/curing temperature: 23ºC/23ºC; 3 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
100%
115
100%
54
100%
20
100%
24
100%
3
91%
76
91%
66
91%
20
91%
24
91%
4
86%
101
86%
49
86%
20
86%
25
86%
3
77%
150
77%
52
77%
21
77%
26
77%
4
70%
44
70%
40
70%
20
70%
25
62%
4
62%
97
62%
43
62%
20
62%
23
55%
4
55%
76
55%
46
55%
21
55%
25
40%
3
47%
48
47%
43
47%
21
47%
25
33%
3
40%
110
40%
51
40%
19
40%
23
26%
3
72
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
33%
78
33%
41
33%
20
33%
24
18%
5
26%
177
26%
41
26%
21
26%
25
18%
174
18%
43
18%
21
18%
24
Count
12
12
12
12
10
Average
104
47
20
24
4
StdDev
44
7
1
1
1
CV
0,4
0,2
0,03
0,03
0,2
Can 2
99%
107
99%
45
99%
19
99%
24
99%
11
92%
122
92%
41
92%
20
92%
24
92%
8
85%
68
85%
43
85%
20
85%
25
85%
4
78%
105
71%
44
78%
21
78%
25
78%
4
71%
358
65%
43
71%
20
71%
24
71%
9
65%
265
57%
45
65%
20
65%
23
65%
14
57%
141
43%
39
57%
20
57%
24
57%
9
51%
183
39%
43
51%
19
51%
24
51%
3
43%
246
43%
19
43%
23
43%
19
39%
170
39%
20
39%
24
39%
7
Count
10
8
10
10
10
Average
176
43
20
24
9
StdDev
89
2
1
1
5
CV
0,5
0,05
0,03
0,03
0,6
sr
71
5
1
1
4
R.L.
195
15
2
2
10
a
10
8
10
10
10
b
9
7
10
10
8
Repeatability
NR
NR
R
R
NR
6396 GEMB3: 5 days of aging; can/curing temperature: 23ºC/23ºC; 2 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
63%
53
63%
87
63%
22
63%
24
63%
3
59%
44
59%
82
59%
21
59%
24
59%
8
54%
55
54%
83
54%
21
54%
24
54%
6
49%
61
49%
85
49%
21
49%
24
49%
5
44%
69
44%
80
44%
21
44%
24
44%
9
Count
5
5
5
5
5
Average
56
83
21
24
6
StdDev
10
3
0,4
0,3
2
CV
0,2
0,03
0,02
0,01
0,4
Can 1
64%
27
52%
83
64%
19
57%
24
57%
4
57%
49
47%
83
57%
22
52%
24
52%
7
52%
64
41%
82
52%
21
47%
25
47%
7
47%
64
34%
82
47%
22
41%
24
41%
8
73
41%
42
41%
21
34%
13
34%
22
34%
24
34%
6
Count
6
4
6
5
5
Average
43
83
21
24
6
StdDev
20
0,4
1
0,3
2
CV
0,5
0,005
0,05
0,01
0,3
sr
16
2
1
0,3
2
R.L.
44
5
2
1
6
a
5
4
5
5
5
b
5
4
4
5
5
Repeatability
R
R
NR
R
R
6396 GEMB3: 5 days of aging; can/curing temperature: 23ºC/23ºC; 3 cm mould gap
Can 1
%LIC
PEtot
%LIC
Alpha
%LIC
Tmin
%LIC
Tmax
%LIC
Pmax
57%
73
57%
76
62%
21
62%
24
62%
6
52%
60
52%
75
57%
21
57%
24
57%
6
47%
44
47%
73
52%
21
41%
24
52%
5
41%
78
47%
20
47%
6
41%
20
41%
5
Count
4
3
5
3
5
Average
64
75
21
24
6
StdDev
15
2
0,5
0,1
1
CV
0,2
0,02
0,02
0,005
0,1
Can 2
61%
78
61%
66
61%
20
61%
24
61%
10
55%
52
55%
84
55%
21
55%
24
55%
10
44%
42
50%
80
50%
21
50%
24
50%
12
38%
51
44%
72
44%
22
44%
25
44%
10
31%
36
38%
69
38%
21
38%
23
38%
12
31%
70
31%
21
31%
24
Count
5
6
6
6
5
Average
52
74
21
24
11
StdDev
16
7
1
1
1
CV
0,3
0,09
0,03
0,03
0,1
sr
16
5
0,5
1
1
R.L.
43
14
1
2
3
a
4
3
5
3
5
b
4
3
4
3
0
Repeatability
R
R
NR
R
NR
74
Appendix 4.
Results of the repeatability trials for previous study on
the AltaFoam Monitor
%LIC
Tmin
Tmax
PEtot
Pmax
Alpha
64
10,8
26,5
197,3
19,9
26,2
56
12,7
26,5
192
22,4
25,6
50
12,5
26
227
16,6
25,6
44
12,5
26
247,8
17
28
36
12,5
26,1
241,3
32,4
26
Count
5
5
5
5
5
Average
12,2
26,2
221,1
21,7
26,3
Stdev
0,8
0,3
25,3
6,4
1,0
60
11,3
26,6
198,2
15,5
28,8
54
12,3
26,5
170,4
19,3
33,9
48
10,4
26,1
213,3
25,9
29,6
41
12
26,1
210
18
28
35
12,6
26,1
220
29,5
26,1
Count
5
5
5
5
5
Average
11,7
26,3
202,4
21,6
29,3
Stdev
0,9
0,2
19,5
5,8
2,9
65
12,9
26,6
181,8
24
30
59
15,4
26,6
201,8
14
25,5
54
13
26,2
228,1
26,6
26,7
48
12
26,3
224,4
18,8
28,9
41
11,7
26,3
249
18,9
27,3
Count
5
5
5
5
5
Average
13,0
26,4
217,0
20,5
27,7
Stdev
1,5
0,2
25,8
4,9
1,8
Can 1
Can 2
Can 3
75
Appendix 5. Results of quick tests of formulation 6459 GWMB3
Figure 8.1 Foam analysis of the formulations of base formulation 6459 GWMB3, in paper and in
wooden mould, at 23/23ºC and at 5/5ºC
76

AltaFoam Monitor Optimization Chemical Engineering

Transcription

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