styrene-butadiene rubber latex polymers

STYRENE-BUTADIENE RUBBER LATEX POLYMERS WITH IMPROVED
AUTO-ADHESION
K. Don Kim, Ph.D., Senior Scientist, OMNOVA Solutions Inc., Akron, OH
Tibor Pernecker, Ph.D., Senior Scientist, OMNOVA Solutions Inc., Akron, OH
Tim Saddow, Sr. Market Development Manager, OMNOVA Solutions Inc., Chester, SC
Abstract
Continuously decreasing availability and increasing costs create incentives to identify suitable
alternatives to natural rubber. Adhesive formulators have blended natural rubber latex with small
amounts of styrene-butadiene latex, albeit with a negative impact on adhesive performance. For some
pressure sensitive adhesive applications natural rubber has been hard to replace due to its superior autoadhesion characteristics, low tack and good compatibility with tackifiers. Newly engineered SBR latexes
might enable adhesive formulators to substantially substitute SBR for NR. Such latexes offer improved
auto-adhesion through molecular architecture and polymer characteristics. These new SBRs are fully
miscible up to 20% with NR, and the homogeneous blends show the same or better autohesion
properties as natural rubber in a certain ratio. The autohesion characteristics are gradually changing with
increasing SBR concentration higher than 20%.
In this paper we discuss the design of new synthetic SBR which can be blended in with NR at high
concentrations without sacrificing adhesive performance for cold seal, tamper evidence, and similar
applications. The SBR latexes are fully miscible up to 20% with NR and the homogeneous blends show
the same or better (90/10 NR/SBR) autohesion properties as natural rubber. Autohesion gradually
deteriorates with an increasing SBR concentration over 20%. However, natural rubber’s low tack is
preserved over a wide range of SBR.
Introduction
Natural rubber (NR) was the earliest polymer used in manufacturing pressure sensitive adhesives (PSA).
Its low Tg, excellent ability to bond under light pressure and ease of processing made it ideal for PSA
applications. In today’s applications it is typically used as a raw material to formulate adhesive products.
Relative to other polymers, natural rubber is limited by its high molecular weight, low miscibility with
low molecular weight resins, low polarity and low UV and thermo-oxidative stability resulting in
discoloration during the lifetime of a PSA product [1, 2]. Over several decades, NR gradually has been
replaced by versatile pure acrylics in formulating PSA, but in some applications it appears to be difficult
to replace it due to its unique characteristics. One such feature is its autohesion, also known as autoadhesion or self adhesion. In cold seal or tamper evident envelope adhesives the choice of the adhesive
is based on natural rubber’s ability to quickly form a strong autohesion contact. In these applications,
after the formation of adhesion contact by two NR layers, fast polymer diffusion commences, the
interface between layers begins to disappear over time and a strong cohesive bond forms between the
two sides. The NR-NR interface becomes an organic part of a NR film. Upon initiating the separation of
the interface, i.e., opening a mailing envelope, a NR adhesive typically delaminates from the carrier
paper or film and provides tamper evidence. Diffusive bonding provides the strong interaction at the
interface.
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Diffusion theory of polymers describes such a phenomenon with clarity [3]. In order for diffusion
bonding to take full effect, high molecular mobility at the interface, good compatibility, and sufficiently
high molecular weight must be met, so that fast autohesion can occur [4]. According to the theory of
polymer interfaces, a full cohesive strength is reached when the polymer molecules at an interface
diffuse a distance comparable to their radius of gyration and form large number of molecular
entanglements [5, 6]. For high molecular weight polymers like polybutadiene and polyisoprene (NR),
the interdiffusion process is completed within 3 seconds at room temperature [7]. This implies that
autohesion of NR is practically instantaneous, making it ideal for selected adhesive applications. The
excellent autohesion feature of NR represents a key experimental obstacle, however, for studying its
autohesion by traditional “T-peel” or any other mechanical test method.
For selected applications such as deep freezer and low temperature adhesive, high performance and
packaging tape, NR is not being used exclusively but, instead, it is blended with low molecular weight
acrylics and styrene butadiene resin (SBR) latexes for enhanced performance and cost effectiveness.
Optimization of blended compositions however is cumbersome using mechanical testing and other
methods, like small angle neutron scattering, and these methods are not readily available to formulators.
Probe tack experiments are well documented in the PSA industry. Creton and coworkers [8] conducted
extensive and detailed investigations of model adhesives using a customized probe tack analyzer
combined with in situ optical observation. Their experiments focused on adhesion between a flat steel
probe and an adhesive layer. Unfortunately, this method can not be directly applied for studying
autohesion of NR/SBR blends because the cohesive strength of the adhesive sample is often greater than
the adhesion between a steel probe and the adhesive, resulting in complete delamination of the adhesive
from the steel probe. We resolved this problem by using paper saturated with NR and NR/SBR as a test
specimen in probe test experiments and, after determining appropriate test conditions, successfully used
the probe tack test method for optimization of the composition of NR/SBR blends.
In this paper we discuss the value proposition behind NR replacement with a newly developed synthetic
SBR, the performance of progressively increasing SBR content blends, as well as the limits of
replacement based on the compatibility of the two elastomers. In the process, we describe a unique
technique to measure autohesion of NR.
Economic Retrospective
Natural rubber is an elastic hydrocarbon polymer derived from the sap of plants such as the Para rubber
tree, Hevea Brasiliensis. According to the International Rubber Study Group [11], total NR and
Synthetic Rubber (SR) production reached 23.6 million tons in the twelve months ending September
2008, around 0.7 million tons higher than at the same point in 2007. SR accounted for 13.5 million tons
(57%) and NR accounted for 10.1 million tons (43%). Although the bulk of rubber produced is
synthetic, derived from petroleum, NR pricing historically has tracked prevailing global price of West
Texas Intermediate crude oil, as shown in Fig. 1.
240
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160
140
120
100
80
60
40
20
0
Crude $/Barrel
140
120
100
80
60
40
20
Crude Oil WTI
NR TSR 20
Jan-2009
Nov-2008
Jul-2008
Sep-2008
Mar-2008
May-2008
Jan-2008
Nov-2007
Sep-2007
Jul-2007
May-2007
Jan-2007
Mar-2007
Nov-2006
Sep-2006
Jul-2006
May-2006
Jan-2006
Mar-2006
Nov-2005
Sep-2005
Jul-2005
May-2005
Jan-2005
Mar-2005
0
NR Cents/lb
160
NR Latex
Figure 1. NR TSR 20 and NR Latex versus Crude Oil Pricing [12].
Until the early 2000s, natural rubber and NR latex have experienced slow demand growth and declining
real dollar prices. However, over the past 3-4 years, rapid industrial growth in China, India, Eastern
Europe, and SE Asia has translated into a greater consumption of NR. Greater demand, along with
limited reinvestment in plantations, has resulted in dramatic fluctuations in NR and latex pricing. NR
latex reached an all time high in August 2008 of $1.80/dry lb, while NR reached an all time high in
October 2008 of $1.48/dry lb.
NR prices have seen a significant price decline since September/October 2008 reflecting concerns over
the impact of the global economic slowdown (lower consumption) and coming off the peak production
season during the third quarter (higher output).
What Can an Adhesive Formulator Do?
Adhesive formulators using NR latex have seen significant price fluctuations in their raw materials in
the last few years for the reasons just described. Continued price volatility and uncertainty should be
considered when formulating decisions are made.
Engineered synthetic SBR latexes enable the water based adhesive formulator to potentially replace a
portion of the NR latex with a synthetic product without sacrificing product performance. In addition to
the performance evaluation of a blended formula, the economics must be evaluated. Fig. 2 shows the
change in raw material costs of NR latex and SBR using 40% styrene and 60% butadiene monomers
ratio for a representative SBR in PSA, as well as two different blends of NR latex and SBR [12].
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120
100
Cents/Dry Lb
80
60
40
20
0
Jan-20 2005
May2005
Sep2005
Jan2006
SB Change
May2006
Sep2006
NR Latex Change
Jan2007
May2007
Sep2007
60%NR:40%SB
Jan2008
May2008
Sep2008
80%NR:20%SB
Figure 2. RM Price Change - Jan. 2005 – Dec. 2008, NR Latex, SBR & Blended Options Source:
CMAI 2009 Data, does not include production, processing or freight costs
The following conclusions can be derived from Fig. 2:
! Blending SBR latex with NR latex lowers formulated raw material costs.
! Over the four year period shown, NR latex increased 60%, while the blended latex increased 42
– 52%, saving the adhesive formulator 13 – 26% in raw material costs.
Doing the research now on how to formulate with SBR latex will give the adhesive formulator the
ability to switch based on economics. Evaluating the price/performance relationship of a blended
formulation allows for reacting quickly to future market changes.
Experimental
SBR Latex Synthesis
SBR latex was synthesized with a typical emulsion polymerization method in a pressurized reactor.
Styrene, butadiene, and carboxylic acid are the primary monomers, and surfactant and other additives
including an initiator are charged to create the desirable molecular weight, particle size and gel content.
Both chemistry and process tools were utilized to precisely control the synthetic polymer’s molecular
weight, its distribution and polymeric chains architecture. Using experimental designs, we determined
the optimum synthetic polymer composition and latex physical properties to emulate NR. Physical
properties of the synthetic SBR and NR latexes are shown in Table 1, hence the methodologies used to
measure and determine the physical parameters are described below. The NR latex for our study was
LA-XT natural rubber from Dynatex and was used without modifications.
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Table 1. Physical Properties of Natural Rubber and SBR
Property
Natural Rubber
SBR
Glass transition temperature (Tg)
! 64 oC
! 50 oC
Gel content
50 %
68 %
Molecular weight, Mw
10, 943,000 g/mole
69,700 g/mole
Polydispersity, Mw/Mn
Critical entanglement molecular weight,
Me
Molecular weight between crosslink
points, Mc
* From reference [9]
66.0
8.6
4,100 g/mole
3,500 g/mole
5,000 g/mole*
460 g/mole
Sample Preparation
The face stock was prepared by saturation of the 42 gsm (28-lbs) crepe paper with natural rubber latex
using a laboratory roll padder. The saturated sheets were air dried for 2 hours, then placed in an oven at
93°C for 5 minutes. The saturated paper created an anchorage with the latex film in it.
The NR latex was mixed with SBR latex providing six samples with NR/SBR ratios of 100/0, 90/10,
80/20, 70/30, 60/40, and 0/100. Free films of each sample were made using Meyer rod on silicone
release liner. These films were dried under room temperature for 15 min and subsequently in a 93oC
oven. The thicknesses of the dried films were between 25 and 35 µm. Three layers of each film were
laminated to a resulting in 75 to 105 µm thick film of each. The sheets were placed in the oven under
weight at 50°C overnight to provide the enough annealing time between film and saturated paper.
Autohesion Testing
The instrument used for the measurement of autohesion is TA.XT plus Texture Analyzer manufacture
by Texture Technologies shown in Fig 3. It has a stainless steel cone type probe connected to the probe
carrier, which is moved vertically. During the sample testing, the force vs. distance between the probe
tip and the bottom adhesive film were recorded by a computer.
Figure 3. Texture Analyzer (Texture Technologies, Model TA.XT)
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The saturated paper laminated with latex film was placed in housing unit under probe as a stationary
adhesive layer. For the top layer, the probe tip was wrinkle free wrapped with the piece of same
laminated paper. A Peltier plate which was located under the specimen docking area maintained a
temperature of 23°C. This set-up allowed an adhesive film to come in contact with the film and the force
could be recorded during upward movement of probe.
The autohesion test can be divided into two distinctively sequential steps. First is the bonding or
compression step, where the probe, covered with saturated paper, comes in to contact with the stationary
specimen and keeps it under compression for a predetermined period of time. Debonding follows this
step during which, at constant velocity, the probe separates from the stationary saturated paper at a
constant velocity. Test conditions were identified by finding the minimum required compression force,
contact time, and probe speed for appearance of fibrillation, fibril formation at separation of NR-NR
specimens. An example of the force vs. distance is shown in Fig. 4. Four different stages can be
distinguished during the debonding process; (a) linear, elastic deformation obeying Hook’s law, (b)
stress relief by cavity germination, (c) evolution of fibril structure, and (d) fibril failure. The optimum
testing conditions were 10 sec contact time, 10 lbf compression force, and 0.05 mm/sec probe speed.
Probe Tack Force
The tack force was measured using a stainless steel probe and it was defined as the value of peak force
recorded between the stainless steel probe surface and the stationary latex film samples during vertical
motion of the probe.
Glass Transition Temperature (Tg)
A Differential Scanning Calorimeter (DSC Q100 from TA Instrument) was used to measure glass
transition temperature, Tg, to detect the compatibility between NR and SBR. Samples of latex films were
o
o
o
scanned as temperature changed from -90 C to 125 C at a rate of 15 C/min in a nitrogen atmosphere.
Figure 4. Typical graph of force versus debonding distance during separation process
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Critical Entanglement Molecular Weight (Me)
The AR-2000 advanced rheometer from TA Instrument was used to measure viscoelastic properties of
NR and SBR films. Films were prepared by drying at room temperature for 48 hrs. Dynamic mechanical
o
analysis (DMA) measurements were conducted by heating the samples at 3 C/min, and 10 rad/sec
frequency 8 mm diameter parallel plate was used with 2.5 mm sample thickness in the range of
o
temperature from -80 to 250 C. The following equation was used to calculate Me. [9]
!p RT
Me =
(1)
Gno
7
Where, "p is the density of polymer, R is the gas constant (8.31 x 10 dyne cm/mol K), and T is the
o
absolute temperature for the onset of the rubbery plateau. Gn is determined from the point where tan #
shows the minimum value in Fig. 5.
Average Molecular Weight Between Crosslink Points (Mc)
Mc was determined with the insoluble material swollen in a solvent. The dried polymer was
encapsulated in a sealed PTFE membrane filter and tumbled in a sealed vial of toluene for 24 hrs. After
24 hrs, the vial was removed from the rotator, the sample rinsed with clean toluene, and any surface
solvent was quickly blotted with absorbent lint- less towel. After weighing the swollen gel, a sample was
o
placed on an absorbent towel in the hood for 30 min and then dried in the oven at 100 C for an hour.
The dry gel was weighed.
Flory-Rhener equation describes the equilibrium swelling theory well and useful for calculation of Mc to
evaluate the degree of crosslinking related to Me. [9]
V1 ! p $ 1/ 3 ' $ / 2
Mc =
(2)
' ln (1 ' $ ) & $ & % $ 2
"
"
#
#
Where, $ is the volume fraction of polymer in the solvent, V1 is molar volume of solvent, "p is the
density of the dry polymer, and ! is the Flory-Huggins polymer-solvent interaction parameter.
1.000E10
3.000
1.000E10
7-15-08
Temperature Ramp for Natural Rubber
1.000E9
1.000E9
2.500
1.000E8
1.000E8
1.000E7
1.500
tan(delta)
1.000E7
G'
1.000E6
1.000E6
1.000
1.000E5
1.000E5
G"
Tan(delta)
10000
0.5000
10000
853-057-1-0407o
PSA parallel plates used. Frequency = 10 rad / sec.
1000
0
-100.0
-50.0
0
50.0
100.0
temperature (°C)
150.0
(a) Natural Rubber
245
200.0
1000
250.0
G'' (dyne/cm^2)
G' (dyne/cm^2)
2.000
1.000E10
3.000
1.000E10
9-25-08
Temperature Ramp for SBR
1.000E9
1.000E9
2.500
1.000E8
1.000E8
2.000
tan(delta)
1.000E7
1.500
1.000E6
1.000E6
G'' (dyne/cm^2)
G' (dyne/cm^2)
G'
1.000E7
G"
1.000
1.000E5
1.000E5
Tan(delta)
10000
0.5000
10000
SBR-0435o
PSA parallel plates used. Frequency = 10 rad / sec.
1000
0
-100.0
-50.0
0
50.0
100.0
temperature (°C)
150.0
200.0
1000
250.0
(b) Styrene Butadiene Rubber
Figure 5. DMA Curves of NR and SBR used for calculation of Me
Results and Discussion
Autohesion of Natural Rubber and SBR
During the debonding stage of autohesion experiments (Fig. 6-B), sample failure occurred at the SBRSBR interface without fibril formation along the separation surface, while extensive fibrillation was
observed with NR-NR samples (Fig. 6-A). After reaching the peak force value, widespread cavity
germination took place with NR samples. The cavity walls oriented in the direction of the applied stress
end formed elongated fibril structures.
A
B
C
D
E
F
Figure 6. Free films of Natural Rubber/SB blends and their corresponding probe
tack curves: A – 100% Natural Rubber (NR), B – 100% SB, C – 90/10 NR/SB, D –
80/20 NR/SB, E – 70/30 NR/SB, F – 60/40 NR/SB, (The line in insert C marks the
integration limit for area calculation)
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Upon further deformation, additional cavities formed within the fibrils and some of the primary fibrils
split in to finer ones. This break up process continued, along with thinning of the primary fibrils, until
the applied stress overcame the cohesive force of the individual fibrils, resulting in cohesive failure
without any sign of the original NR-NR interface. In addition to elastic deformation of the primary
fibrils, the stress energy was also relived by continuous cavitations inside the elongated fibrils and their
break up.
On the molecular level, during the debonding process of two polymer interfaces, the stress energy can be
dissipated by the work against secondary forces and by a chain pull-out mechanism, i.e., by
disentanglement of diffused polymer chains at the interfacial layer. The cohesive strength of an
interfacial layer depends on entanglement density (De). When the De value is high, the strong secondary
electrostatic forces delay individual chain disentanglements, and the interface appears stronger. After
stress energy reaches a critical value, the entangled chains start to orient and stretch into the direction of
the applied stress. Further deformation leads to disentanglement of the individual chains and structural
failure.
Using the entanglement density of the individual polymers we can estimate failure mechanism of SBRSBR or NR-NR interfaces. The entanglement density is the ratio of the weight average molecular weight
of the soluble fraction (Mw) and the entanglement molecular weight (Me) i.e., De = Mw/Me. Literature
suggests that only polymers which have Me > 10,000 g/mole are able to show fibrillation during the
debonding process [10]. While this is valid for the debonding of SBR-SBR interface during the
autohesion experiments, it is not valid for the NR-NR interface. The Me and the calculated De values for
NR and SBR from equation (1) are 4,100 and 3,500 g/mole and 2,656 and 20, respectively. (Table 1)
The low peak force and the clean failure at the SBR-SBR interface suggest that the failure occurred by a
simple chain pull out mechanism due to lack of sufficient interaction between the polymer chains and
low De value of SBR compared to NR. The Me value of natural rubber is similar to that of SBR, but its
high soluble fraction (50% compared to 32% for SBR, see Table 1) and large De i.e., average number of
entanglements per chain, provide sufficient cohesive energy for fibril formation during the debonding
stage. Both elastomers contain a substantial amount of gel (Table 1). The molecular weight between the
crosslink points (Mc) was calculated from equation (2) and is not high enough (<1000, see Table I) to
form entanglements with the linear polymer chains in the case of SBR. On the other hand, in NR the Mc
is slightly higher than Me giving an opportunity for entanglement formation between longer network
chains and linear NR chains, therefore contributing to fibril formation during deformation.
Autohesion of NR/SBR blends
The deformation characteristics for NR-SBR blends are similar to those of NR. A 10% addition of SBR
to NR increased the initial peak force (Fig. 7) and had a fibril “reinforcement” effect during the
debonding process in NR/SBR autohesion experiments (Fig. 6-C). In these experiments the sample
failure was not cohesive i.e., fibril break, but delamination from either the upward moving probe’s
surface covered by paper saturated with the NR/SBR (90/10) blend or from the stationary saturated
paper. The fibrils appeared to be too strong to break. An increase of SBR to NR ratio led to lower peak
force, work of adhesion (area under the curve), initial slope during the debonding process (Figure 7-a),
and fibril failure without delamination from either saturated paper surfaces (Figure 6-D, E, F). One
possible explanation for the fibril “reinforcement” is the potential plasticization of the polyisoprene
molecules by the low molecular weight poly (styrene-butadiene) molecules. The presences of low
247
molecular weight poly (styrene-butadiene) chains promote alignment of the stereo-regular polyisoprene,
similarly to the well known stress induced crystallization with cis-polyisoprene. In NR/SBR blends with
20% or higher SBR concentration phase separation was observed (see picture in Figure 6). The NR/SBR
blend free films became opaque with increasing SBR concentration. The change in visual appearance
was substantiated by DSC. As it is shown in Fig. 8, the 90/10 NR/SBR blend has only one Tg which is
close to that of NR. At higher than 20% SBR concentration, a second small transition appears and
becomes pronounced with increasing SBR concentration (the medium sized endotherm, just after the
glass transition temperature of NR, is commonly referred to as enthalpic recovery).
Total Area vs. Blend Ratio
4
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Area kg/mm
Initial Slope
Initial Slope vs. Blend Ratio
3.5
3
2.5
2
1.5
1
0.5
0
0
20
40
60
80
100
0
20
wt% SBR
60
80
100
wt% SBR
(a)
(b)
Peak Force vs. Blend Ratio
P robe!T ac k!F orc e!vs .!B lend!R atio
2.5
0.5
2
fo rc e!(lb s /in )
Peak Force, lbs
40
1.5
1
0.5
0
0.3
0.2
0.1
0.0
0
20
40
60
80
100
0
wt% SBR
(c)
0.4
20
40
60
wt!%!S B R
(d)
Figure 7. Effect of NR/SBR blend composition on initial slope, work of
adhesion, peak force, and probe tack force
248
80
100
The DSC data show that the SBR is fully miscible toNR, up to 20%. Above 20%, the SBR/NR interface
influences fibril deformation during debonding (Fig. 7). The De value of SBR dominates over that of NR
(20 compared to ~2000), gradually deteriorating the autohesion properties of natural rubber (Fig. 6- D,
E, F) and its ability to dissipate energy during the debonding process. At high levels of SBR, the
presence of gel, which is incapable of forming chain entanglements neither with SBR nor with NR
chains, gradually limits a blend’s ability to form fibrils during the debonding process, and subsequently
dissipate stress by viscoelastic deformation.
0.2
Natural Rubber
-64.05°C(H)
0.0
-64.74°C(H)
Heat Flow (W/g)
-0.2
NR/SBR=90/10
-64.42°C(H)
-47.34°C(H)
NR/SBR=80/20
-48.77°C(H)
NR/SBR=70/30
-49.01°C(H)
NR/SBR=60/40
-64.72°C(H)
-0.4
-64.42°C(H)
-0.6
-0.8
-50.14°C(H)
SBR
-1.0
-100
Exo Up
-80
-60
-40
-20
0
20
Temperature (°C)
40
60
Universal V4.3A TA Instruments
Figure 8. DSC Curves of blended latex samples
Probe Tack
In probe tack experiments (Fig. 7-d) the low tack of NR was preserved over a wide range of blended
compositions because of the low adhesion of NR/SBR blends to the stainless steel probe. In these
experiments the cohesive strength of NR and NR/SBR blends, which was mainly provided by NR, was
higher than the blends’ adhesion to stainless steel.
249
Conclusions
We have shown that engineered synthetic SBR latexes can be blended with NR for adhesives in cold
seal, tamper evident and similar applications. These SBR latexes are fully miscible up to 20% with NR,
and the homogeneous blends show the same or better (90/10 NR/SBR) autohesion properties as natural
rubber. Autohesion gradually deteriorates with an increasing SBR concentration over 20% by weight.
However, natural rubber’s low tack is preserved over a wide range of SBR concentrations in NR/SBR
blends.
Literature Citations
1. Istvan. Benedek, Pressure Sensitive Design and Formulation, Application, vol. II,
Martinus Nijhoff Publisher and VSP, 2006
2. Alphonsus V. Pocius, Adhesion and Adhesives Technology, Hanser, 2002
3. S.S. Voyutskii, Autohesion and Adhesion of Polymers, Interscience, New York, 1963
4. U. Giese, R.H. Schuster, KGK Kautchuk Gummi Kunstoffe, 54. Jahrgang, 12, 600
(2001)
5. Y. Liu, J.C. Haley, K. Deng, W. Lau, M. A. Winnik, Macromolecules, 40, 6422 (2007)
6. J.C. Haley, Y. Liu, M.A. Winnik, W. Lau, J. Coat. Tecnol. Res., 5 (2), 157 (2008)
7. C.M. Roland, G.G. Bohm, Macromolecules, 18, 1310 (1985)
8. R. Schach, Y. Tran, A. Menelle, C. Creton, Interdiffusion and Tack at Interfaces
Between Immiscible Polymer Melts, Proceedings of the 29th Annual Meeting of The
Adhesion Society, Jacksonville, USA, 2006
9. L.H. Sperling, Introduction to Physical Polymer Science, J. Wiley & Sons (1992)
10. A. Zosel, Int. J. Adhesion and Adhesives, 18, 265 (1998)
11. Rubber Industry Report, International Rubber Study Group, Vol. 8, No 4-6, OctoberDecember 2008
12. CMAI Price Database, 2009
Acknowledgments
The authors would like thank Mr. Ian Everhard to conduct the autohesion tests, and the Analytical
Solutions Group at the Akron Technology Center for DSC and Rheometer testing of the samples.
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TECH 32 Technical Seminar Speaker
Styrene-Butadiene Rubber Latex Polymers with
Improved Auto-Adhesion
K. Don Kim, Ph.D., OMNOVA Solutions Inc.
K. Don Kim is a senior scientist in Akron Tech Center of OMNOVA Solutions Inc. Kim
received his Ph.D. in polymer science and engineering from Lehigh University in 1993.
His specialty is emulsion polymerization, suspension polymerization, colloidal and
surface chemistry, and polymer chain interdiffusion. Kim has worked for Hansol
Chemicals in South Korea, Reichhold Inc, and OMNOVA Solutions Inc since 2001. In
his career in the chemical industry, he has focused on paper coating, floorcare coating
and pressure sensitive adhesives. Kim holds nine patents and co-authored some technical
papers in polymer science.
He can be reached at [email protected].
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