c.m. roland naval research laboratory gary s. buckley cameron university
TRANSCRIPT
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Improving Performance of Rubber Materials Through Blending
C.M. RolandNaval Research Laboratory
Gary S. BuckleyCameron University
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Outline
•A little terminology
•Work with hydrogels
•Can this shift to rubber materials?
•Materials used in rubber work
•Results
•Conclusions
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A Little Terminology
Crosslink – a covalent bond between two separate polymer molecules
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Work with Hydrogel Materials
Jing Ping Gong and Yoshinori Katsuyama, Advanced Materials, 15(14), 2003.
Single Network Double Network
Single Network Double Network (0.4 MPa) (17.2 MPa)
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Key factors: 1. The two networks were homogeneous. 2. The difference in crosslink densities was maximized.
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Can this idea translate to rubber materials?
Two selected rubber materials:
EPDM – contains double bonds and can be crosslinked with sulfur
EPM – contains no double bonds and cannot be crosslinked with sulfur
The idea:Blend EPDM and EPM followed by crosslinking with sulfur to see if mechanical properties are improved
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0 0.5 1 1.5 2 2.5 3 3.5 40
0.5
1
1.5
2
2.5
3
3.5
Comparison of Higher Modulus Materials
0% EPM 0.625 phr S 50% EPM 1.4 phr S
Strain (mm/mm)
Str
ess
(MP
a)
Tensile Strengths
Is the EPM chemically a part of the network?
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Did EPM become a bonded part of the network?
All EPM should be soluble if not a chemical part of network
Soxhlet extraction to determine gel fraction
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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60.5
0.6
0.7
0.8
0.9
1
1.1
Gel fractions vs. phr Sulfur
0% EPM 50% EPM
phr S
Gel
Fra
ctio
n
Gel fractions
Indicates that EPM was not a chemical part of the network
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Network Density
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60.0E+001.0E-052.0E-053.0E-054.0E-055.0E-056.0E-057.0E-058.0E-059.0E-051.0E-04
Network Density vs. phr S
0% EPM 50% EPM
phr S
Net
wo
rk D
ensi
ty (
mo
l/cc
)
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Tensile Strength and Network Density
0.0E+00 1.0E-05 2.0E-05 3.0E-05 4.0E-05 5.0E-05 6.0E-05 7.0E-05 8.0E-05 9.0E-050
0.5
1
1.5
2
2.5
3
3.5
4
Mechanical Properties vs. Network Density
0%EPM (TS) 50%EPM (TS)
Network Density (mol/cc)
Ten
sile
Str
eng
th (
MP
a)
Is there a homogeneity issue?
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Are EPDM and EPM homogeneous initially?
C-C bond length:
~ 0.15 nm
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Potential Applications – Ballistics
Bad response Good response
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Conclusions
•Blended EPDM and EPM crosslinked with sulfur provides better tensile strength than crosslinked EPDM
•Blended EPDM/EPM tensile strengths continue to increase even as the network density levels off
•The increase in tensile strength of the blended material is modest – not on the order of the hydrogel work
•The EPDM/EPM system is not particularly homogeneous - work remains to be done to see if its homogeneity increases as the cure package increases
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Street lights
Fireworks
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