Peroxide‐based crosslinking of solid silicone rubber, part II: The counter‐intuitive influence of dicumylperoxide concentration on crosslink effectiveness and related network structure

Application of elastomers in general demands the conversion of their soluble networks into crosslinked structures. This abrupt change causes several modifications, both in the atomic/molecular level and at the macro‐scale. In this study, solid silicone rubber (high molecular weight poly(dimethylsilo...

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Bibliographic Details
Published in:Journal of applied polymer science 2023-08, Vol.140 (31), p.n/a
Main Authors: Azevedo, M., Monks, A.‐M., Kerschbaumer, R. C., Schlögl, S., Saalwächter, K., Walluch, M., Consolati, G., Holzer, C.
Format: Article
Language:English
Subjects:
crosslink density
Crosslinking
Crystallites
Crystallization
dicumylperoxide
Elastomers
free volume
Materials science
Molecular dynamics
network morphology
Polydimethylsiloxane
Polymers
Rubber
silicone
Silicone rubber
Silicones
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Summary:Application of elastomers in general demands the conversion of their soluble networks into crosslinked structures. This abrupt change causes several modifications, both in the atomic/molecular level and at the macro‐scale. In this study, solid silicone rubber (high molecular weight poly(dimethylsiloxane)), was crosslinked with dicumylperoxide (DCP), a widely used crosslinking agent by the rubber industry. The changes caused by different DCP concentrations were investigated, aiming to bring attention to the molecular transformations, usually neglected when processing‐oriented studies are conducted. DCP concentration showed a limited contribution to the network's molecular dynamics, which was found to be mainly dominated by entanglements. The dominance of entanglements over other molecular constraints, like crosslink points, justifies the threshold and counter‐intuitive behavior of tensile and hardness properties. However, differences were found in the crystallization ability after crosslinking, when the more crosslink points were introduced, the lower the crystallinity was and the less stable the PDMS crystallites were. In addition to providing a deeper understanding of an industrially applied rubber system n terms of the effective concentration of DCP, and the reasoning behind such concentration, the findings of this study add to the state‐of‐the‐art comprehension of elastomeric networks, and how they behave on a molecular level. Solid silicone is usually crosslinked with dicumylperoxide (DCP) for several applications. The curing of an already highly entangled high molecular weight Polydimethylsiloxane (PDMS) network with DCP resulted in crosslinked macromolecular systems without major differences regarding molecular dynamics. However, mechanical properties were improved, with a limited and counter‐intuitive effect of the peroxide concentration on the micro and macro properties.
ISSN:0021-8995
1097-4628
DOI:10.1002/app.54111