Materials

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Materials

Development of Biodegradable
Polyurethane Footwear Soling
Materials
G. Saraswathy, Scientist, CSIR- CLRI, India
15. 11.2013
Council of Scientific and Industrial Research
(CSIR)
MISSION
 To provide scientific industrial R&D that maximises the economic,
environmental and societal benefits for the people of India.
CSIR-Central Leather Research Institute
(Council of Scientific and Industrial Research)
G. Saraswathy- Development of Biodegradable Polyurethane Footwear Soling Materials- 15.11.2013
Recent Head Lines
 Coffee industry responsible for significant plastic
litter
 Food packaging industry can do a lot better
 Plastic bottles litter the solar system
 Super markets hand out 8 billion plastic bags- UK
 Footwear industry ………….!
Social ResponsibilityChallenges of Footwear
Industries
Wastes generated by the footwear
manufacturing - % of world areas
North and Central
America 5%
South America
7%
Rest of the world 3%
Western
Europe 10%
China
47%
astern Europe 3%
Middle East 3%
Asia (excl.
China) 22%
General Solutions for Waste Management
4R’s
 Reduce
 Reuse
 Wear them around / Sell them / Donate them
 Recycle
 Collecting from post-consumers (Nike)
 Separated by materials - Upper fabric - Midsole foam - Outsole
rubber
 Floors of Basket ball court/ Playground surfacing/ Running
tracks
 Energy recovery – Heat/ Power
Rejuvenate
 Rejuvenation using landfill biodegradable additives to make
plastics fade away.
 Shoe soles - Land fill -???
Footwear Soling Materials
Percentage (%)
Leather
8
Polyurethane (PU)
8
Thermoplastic Rubber (TPR)
14
Ethylene Vinyl Acetate (EVA)
9
Poly (Vinyl Chloride) (PVC)
20
Rubber
40
Others
1
Ref: Staikos T, Rahimifard, S. A decision-making model for waste management
in the footwear industry. Intl J Production Res 2007; 45 (18): 4403-4422.
Biodegradable Shoes / Simple Shoes
 The shoe raw materials and
packaging come from
 Vegetable origin polymers
 Fossil organic matter
 Natural fibre
 Recycled cardboard
 Pigments
1. The upper is pieced together
from leather and synthetic
leather waste from the factory
floor using zig-zag stitching.
2. The mid-sole - scrap-ground
foam from factory production.
3. The outsole uses
environmentally-preferred
rubber and Nike Grind material
4. Packaged in a fully recycled
cardboard shoe box.
But we are talking about….
What is Biodegradability?
 Biodegradability is characteristic of natural
substances and materials being assimilated by
micro-organisms, and thus introduced into the
natural cycles.
 Biodegradability testing determines the potential
rate of degradation by biological processes in the
environment.
Need of Biodegradable Shoe Soling material
 Though polyurethane is used only 8% of the global
production of shoes and this figure continuous to
rise for its unique mechanical properties.
 Therefore footwear/ polymer industries have
started to develop low cost PU to replace the
conventional polymer soles.
 The polymeric shoe soles create an enormous
amount of waste that is currently being disposed as
landfill.
Objective of the project
 To prepare and characterize
biodegradable polymer
composites based on PU.
 To determine the physical,
mechanical and degradation
properties of prepared
polyurethane materials for
application as shoe soling
material.
Experimental Procedure
Materials:

Polyol: Polycaprolactone diol (PCL diol).

Diisocyanates: 4,4’-methylenediphenyl
diisocyanate (MDI), Hexamethylene
Synthesis of Segmented PU
Prepolymer Method
2O
C
R
N
C
N
O
HO
OH
R'
diisocyanate (HMDI), Toluene diisocyanate
(TDI), and Isophorone diisocyanate (IPDI).

Chain Extender: Ethylene diamine
(ED),1,4-Butane diol (BD), N-Methyl
diethanol amine (MIDE), Triethanol amine
OCN
R
H
O
N
C
O
R'
O
O
H
C
N
R
NCO
O
R"
(TEA).

Catalyst: Dibutyltin dilaurate (DBTDL).

Solvents: Dimethyl formamide (DMF).

Nanoparticles: Nanoclay and Titanium
prepolymer
reaction with diol
HO
dioxide.

Thermoplastic polyurethane (CPU)
R'
OH
O
H
H
O
C
N
N
C
prepared using PCL as one of the polyol, from
Sigma.
O
R"
O
polyurethane
O
PREPARATION OF PU SHEET BY CASTING
After completion of two step
synthesis of segmented
polyurethanes, the polymer solution
was poured into glass dishes and
dried at 60 °C for 24 h and then
stored in desiccator until use.
Types of PUs synthesized in the laboratory
Preparation of PU Composites
 Properties of Nanoclay (MMT)
 Chemical Name: Hydrated sodium
calcium aluminum silicate
 Nominal Chemical Composition (%):
Al= 9.98, Si= 20.78, H= 4.10 and
0=65.12
 Powder as fine as 20 nanometers
 Molecular Weight (g/mol.): 540.46
 Average Density (g/cm3): 2.35
 Crystal System: Monoclinic
 Abundantly available
 Eco-friendly and cost effective
 Properties of TiO2
Nanopowder
 Appearance: White solid
 Average Density (g/cm3): 4.23
 Contents: Rutile-30-40 wt %;
Anatase-60-70 wt %
 Partical Size: 10-30 nm
 SSA: 50-100 m2/g
 Crystal system: Tetragonal
 Occurs in nature
List of PU composites developed
in the laboratory
Sl.
No
Sample Code
Description
1.
CPU Control
15 % CPU 430218 (15 g of CPU in 100 ml of DMF)
2.
CPU- NC 1%
15 % CPU : NC 1 % (15 g of CPU : 0.1 g NC in 100 ml of DMF)
3.
CPU- NC 2%
4.
CPU- NC 4%
5.
CPU- NC 6%
6.
CPU- TD 1%
15 % CPU : TD 1 % (15 g of CPU : 0.1 g NC in 100 ml of DMF)
7.
CPU- TD 2%
8.
CPU- TD 4%
9.
CPU- TD 6%
SEM Pictures
The outer surface morphology and
corresponding cross section at 1000
magnification of Samples
A) SPU,
B) SPU 2% NC,
C) SPU 2% TD,
D) CPU 2% NC and
E) CPU 2% TD.
Biodegradability Test by Soil Burial Method
 The soil burial test was carried out in two different soils
(red and normal soil) of same locations at garden (CLRI
campus).
 The percentage weight loss of the test films was
calculated by using the relationship:
Weight loss (%) = ((Wi –Wf) / Wi) x 100
where
Wi = initial weight
Wf = final weight of the test sample.

Sample A- PU based on MDI:PCL:BD


Sample B - PU based on MDI:PCL:MIDE
Sample C- CPU 430218 from Sigma
Biodegradability Test Results
Weight Loss (%)
14
% Weight Loss
12
10
30 days
8
45 days
6
60 days
4
90 days
2
0
A
B
Sample Code
C
A – SPU (MDI:PCL:BD), B – SPU (MDI:PCL:MIDE), C - CPU (430218)
Loss of Tensile Strength
Tensile strength, MPa
18
15
12
30 days
9
45 days
60 days
6
90 days
3
0
A
B
C
Sample code
A – SPU (MDI:PCL:BD), B – SPU (MDI:PCL:MIDE), C - CPU (430218)
Physico-Mechanical Properties of
PU sheets as Soling Materials
•
•
•
•
•
Hardness
Density
Tensile strength
Tear strength
Abrasion resistance
70
1.4
60
1.2
Density, g/cc
Hardness, Shore A
Results – Hardness & Density
50
40
30
20
1
0.8
0.6
0.4
NC
TD
Tensile & Tear strength
30
60
20
Max. load/T, N/mm
Tensile Strength, MPa
80
10
0
40
20
0
NC
TD
Abrasion Resistance
Sample code
Abrasion Resistance
CPU Control
37.723
CPU NC 1%
52.328
CPU NC 2%
32.512
CPU NC 4%
51.573
CPU NC 6%
47.904
CPU TD 1%
35.359
CPU TD 2%
22.838
CPU TD 4%
26.719
CPU TD 6%
46.300
Volume Loss, cu.mm
(Volume loss) in mm3
60
40
20
0
Hydrolysis
Sample
code
Thickness
(mm)
Tensile
strength
(MPa)
SPU
Control
SPU
Hydrolysed
0.21
7.66
5.89
0.21
3.72
23.67
CPU
Control
0.59
15.82
823.33
CPU
Hydrolysed
0.93
13.62
Elongation
Reduction in
at break Tensile strength
(%)
after hydrolysis
(%)
Change in
Elongation
after
hydrolysis (%)
51.44
301.87
13.9
57.87
346.89
Summary & Conclusion
• Biodegradable PUs having material properties required for soling
material were prepared.
• The standard stoichiometric ratio of 2:1:1 was optimized for synthesis of
biodegradable PU using HMDI: PCL: BD composition.
• In order to improve the mechanical properties, nanoparticles were added
to commercial and synthesized polyurethanes in various concentrations.
• The concentration of nanoparticles was optimized. Other ingredients
which are normally used in the preparation of PU soles were not used in
the preparation of PU nanocomposites.
• The PU sheets developed with 2% concentration of nanoclay (NC) and
Titanium dioxide (TD) had shown better mechanical properties than the
other PU sheets.
• The mechanical properties of composites are found to meet the standard
specifications for soling materials.
Acknowledgement
 Organizers – UITIC - CLIA
 DST, Govt. of India
 The Director, CSIR-CLRI
THANK YOU
FOR YOUR KIND ATTENDTION

Materials

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