TY - JOUR

T1 - Peroxide-based crosslinking of solid silicone rubber

T2 - part II: The counter-intuitive influence of dicumylperoxide concentration on crosslink effectiveness and related network structure

AU - Azevedo, Maurício

AU - Monks, Anna-Maria

AU - Kerschbaumer, Roman

AU - Schlögl, Sandra

AU - Saalwächter, K.

AU - Walluch, Matthias

AU - Consolati, G.

AU - Holzer, Clemens

N1 - Publisher Copyright: © 2023 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals LLC.

PY - 2023/8/15

Y1 - 2023/8/15

N2 - 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.

AB - 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.

KW - crosslink density

KW - crosslinking

KW - dicumylperoxide

KW - free volume

KW - network morphology

KW - silicone

UR - http://www.scopus.com/inward/record.url?scp=85159811169&partnerID=8YFLogxK

U2 - 10.1002/app.54111

DO - 10.1002/app.54111

M3 - Article

AN - SCOPUS:85159811169

VL - 140.2023

JO - Journal of applied polymer science

JF - Journal of applied polymer science

SN - 0021-8995

IS - 31

M1 - e54111

ER -