Influence of cross-linker concentration on the cross-linking of PDMS and the network structures formed

A.C. Carvalho Esteves, de, J.C.M. Brokken-Zijp, J. Laven, H.P. Huinink, M.-P. Van, G. With, de

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Abstract

The cross-linking of linear di-vinyl-terminated Poly(dimethylsiloxanes) (PDMS) with tetrakis(dimethylsiloxane) was studied in the presence of different concentrations of the cross-linker (H/V = ratio of Si-H groups of the cross-linker and C=C bonds). The consumption of the Si-H and C=C bonds was monitored simultaneously by in situ Confocal Raman Microscopy (CRM) and ATR-FTIR Spectroscopy. When formulations with H/V > 1.0 are cross-linked at low temperature (25 °C) in air and atmospheric humidity conditions, hydrosilylation and secondary reactions occur simultaneously at early stages of the reaction. For H/V = 1.0 the C=C bonds are also consumed by side reactions.Films cross-linked from formulations with different H/V ratios were studied by NMR imaging, swelling/extraction experiments and SEM. Films cross-linked with H/V = 1.0 showed a slower magnetization decay due to the presence of a large percentage of extractable material not connected to the cross-linked network. After extraction, all the films show faster relaxation behavior, explained by the presence of two types of chemical cross-links as well as one type of physical cross-links. These cross-links result from the occurrence of hydrosilylation and secondary reactions and counterbalance each other at different H/V ratios.
Original languageEnglish
Pages (from-to)3955-3966
JournalPolymer
Volume50
Issue number16
DOIs
Publication statusPublished - 2009

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