advances in polyolefin foaming technology...foaming technology foam properties-foam density-closed...
TRANSCRIPT
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
The Dow Chemical Company
Advances in Polyolefin Foaming Technology
Colin Li Pi Shan, Brian Yu, Kyle Kummer
Dow Packaging & Specialty Plastics
Xian Jiang
E.I. du Pont de Nemours and Company, Inc
-
Advances in Polyolefin Foaming Technology
▪ Influence of polymer structure on crystallinity and rheology
▪ Chemical foaming – polymer-property relationships
▪ Ionomer addition for ultra low density foams
2
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Features of Polyolefin Foams
3
➢ Light Weight
➢ Soft and Flexible
➢ Easy to Process
➢ Good Foamability
➢ Low Temperature Use
➢ Recyclable/Sustainable
➢ Safety
Performance FootwearComfort Shoes
Safety EquipmentProtective Mats
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
OBC
Soft blocks
Hard blocks
- High pressure process
- Free radical catalyst
- Polar functionality (VA)
- High melt strength
- High density
- Solution process
- Molecular catalyst
- Non-polar functionality
- Linear, high strength
- Low density
- Solution process,
chain shuttling catalysts
- Non-polar functionality
- Segmented blocks
- Low density, high Tm
EVA POE
Ethylene vinyl-acetate Polyolefin Elastomer Olefin Block Copolymer
4
m
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
0.2
0.4
0.6
0.8
1
1.2
1.4
-100 -75 -50 -25 0 25 50 75 100 125 150
Heat
Flo
w (
W/g
)
Temperature (˚C)
EVA
POE
OBC
Polymer Xc
(%)
Tg (˚C) Density
(g/cc)
EVA 25 -30 0.941
POE 18 -52 0.870
OBC 20 -62 0.877
EVA has higher crystallinity
and higher density (due to VA)
POE has low crystallinity
and low Tg
OBC has low crystallinity,
low Tg, and a high melting
point
*Exo down
DSC Crystallinity
5
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Crystallinity Distribution using Enthalpy Corrected DSC
-30 -10 10 30 50 70 90 110 130
Temperature (°C)
EVA
POE
OBC
Random Copolymer
Flexibility and ToughnessOlefin Block Copolymer
Elasticity and Heat Resistance
6
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Rheology Comparison
*DMS Rheology measured at 190˚C
7
100
1000
10000
0.1 1 10 100
Co
mp
lex
Vis
cosi
ty (
Pa-
s)
Frequency (rad/s)
EVA (2.5MI)
POE (5MI)
OBC (5MI)
30
40
50
60
70
80
90
100
100 1000 10000 100000
Ph
ase
An
gle
(°)
G* (Pa)
EVA (2.5MI)
POE (5MI)
OBC (5MI)
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foaming Technology
Foam Properties
- Foam Density
- Closed cell
- Cell size, distribution
8
Balance of Foaming and Curing
• Melt Strength
• Nucleation and Crystallization
• Crosslinking agent – peroxides, sulphur
• Solubility and diffusivity of blowing agent
Chemical Blowing Agents
– organic and inorganic blowing agents
- azodicarbonamide, OBSH, sodium bicarbonate,
citric acid
Under-Crosslinked
Over-Crosslinked
Good foam cell structure Poor foam cell structure
8
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Experimental
Foam Ingredients
EVA POE OBC*
EVA 100POE 100OBC 100
Luperox 40DC SP2 0.9 0.9 0.99Luperox
40DC 1.35 1.35 1.485AC9000 X Y Z
ZnO* 0.1X 0.1Y 0.1ZZnSt* 0.1X 0.1Y 0.1ZCaCO3 5 5 5
Ingredients pre-compounded and mixed
together in 1.5L Banbury mixer
- Polymer
- CaCO3 + Filler
- Blowing agent + Curatives
Compression Molding
- 110˚C pre-molding, 4 min
- 180˚C foaming/Curing, 8 min
Property Testing of Foams
- Oven aged shrinkage
- Tensile, tear, compression set, resilience*Based on prior experiments, POx level was increased by 10%
for the OBC.
9
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foam Expansion
10
Higher and similar
expansion ratio observed
for EVA and OBC
POE had the lowest
expansion ratio
Expansion Ratio
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Degree of Curing
11
POE cured the fastest and
had the highest degree of cure
OBC cured the slowest and
showed the lowest degree of
cure
EVA showed an intermediate
degree of cure
MDR Torque (dN.m)
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foam Density and Hardness
12
0.10
0.15
0.20
0.25
0.30
0.35
1.35 1.50 1.65 1.80 1.95
Expansion Ratio
EVA
POE
OBC
Density (g/cc)
15
20
25
30
35
40
45
50
55
60
1.35 1.50 1.65 1.80 1.95
Expansion Ratio
EVA
POE
OBC
Shore A Hardness
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foam Strength
13
0
5
10
15
20
25
1.35 1.5 1.65 1.8 1.95
Expansion Ratio
EVA
POE
OBC
Tear Strength (N/mm)
0
1
2
3
4
5
1.35 1.5 1.65 1.8 1.95
Ten
sile
Str
en
gth
, MP
a
Expansion Ratio
EVA
POE
OBC
Tensile Strength (Mpa)Tensile Strength (MPa)
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foam Resiliency
14
52
54
56
58
60
62
64
1.35 1.50 1.65 1.80 1.95
Expansion Ratio
EVA
POE
OBC
Resiliency (%)
20%
30%
40%
50%
60%
70%
1.35 1.50 1.65 1.80 1.95
Expansion Ratio
EVA
POE
OBC
Compression Set (%)
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Foam Shrinkage
Before
Oven
Aging
After
Oven
Aging
(70˚C)
EVA POE OBC
15
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Ionomer Addition for Foaming Control*
Ionomer can be added to introduce secondary ionic crosslinking
Optimizing foaming behavior:
▪ Enhancing melt strength
▪ Stabilizing bubble growth
▪ Controlling the nucleation
Under-Crosslinked
Over-Crosslinked
Enhanced melt strength with ionomer
16
0.5
1
1.5
2
2.5
0.3 0.4 0.5 0.6 0.7 0.8
To
rgu
e (lb
-in
ch
)
Peroxide (pph)
Melt Strength of Foam Compounds (165 C)
EVA
EVA/Ionomer (10phr)
To
rqu
e (
lb-i
nch
)
*C.F. Hsu, R. Chou, W. Whelchel, Y.T. Ou, U.S. Patent 6,528,550 (1999).
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow 17
Avg 175µm Avg 52 µm
POE/OBC Foam PropertiesWith 1 phr
ionomer
1.74 Expansion Ratio 1.69
0.14 Av Density, g/cc 0.16
27.5 Shore A 31
60 Rebound, % 61
53 CSET 50%, 50C/6h 53
353 Avg-Strain at Break 383
2.1 Avg-Stress at Break 3.1
11.4 Type C Tear, N/mm 15.5
Ultra Low Density POE/OBC Foam
Foam Properties
Low levels of ionomer significantly reduces cell size and improves foam strength.
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
Polyolefin polymers can be used to make soft, light weight, and resilient foams
Formulation adjustments are needed to
account for differences in curing and
rheology
▪ EVA - higher foam tear strength
▪ POE, OBC - lower density, softer foams
▪ OBC – excellent dimensional stability and resiliency
▪ Ionomers – cell size reduction, improved foam strength
18
Summary of Foam Properties
-
® ™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
The Dow Chemical Company
Thank You
19