Fragility of unsaturated polyester resins cured with styrene: influence of the styrene concentration
Unsaturated polyester resins cured with varying styrene content (20–50% (w/w)) has been studied by calorimetry (DSC). We have evaluated the values of the heat capacity at the glass transition ΔC p =[ C p,l − C p,g ] T= T g , the values of apparent activation energy Δh *, and the values of the fragil...
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Published in | European polymer journal Vol. 37; no. 11; pp. 2169 - 2176 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
01.11.2001
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Unsaturated polyester resins cured with varying styrene content (20–50% (w/w)) has been studied by calorimetry (DSC). We have evaluated the values of the heat capacity at the glass transition
ΔC
p
=[
C
p,l
−
C
p,g
]
T=
T
g
, the values of apparent activation energy
Δh
*, and the values of the fragility index
m
for each sample. It is found a constant value of
ΔC
p=0.29
J
g
−1
K
−1 for all the samples while
Δh
* and
m
increase with the styrene content. These results discussed in regard with the strong fragile glass-formers concept indicate a character becoming more fragile when the amount of styrene increases. Introducing the “bead concept” proposed by Wunderlich, we show that the average elementary energy barrier that the molecular species (or relaxing units) must overstep during their relaxation process is unchanged whatever the content of styrene. The origin of the variations with the styrene content of the fragility behavior is understood by the increase of the bead number. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0014-3057 1873-1945 |
DOI: | 10.1016/S0014-3057(01)00114-8 |