Influence of cross-linker concentration on the cross-linking of PDMS and the network structures formed
2009; Elsevier BV; Volume: 50; Issue: 16 Linguagem: Inglês
10.1016/j.polymer.2009.06.022
ISSN1873-2291
AutoresA. Catarina C. Esteves, J. Brokken-Zijp, Jozua Lavèn, H.P. Huinink, N.J.W. Reuvers, Mark Van, Gijsbertus de With,
Tópico(s)Analytical Chemistry and Sensors
ResumoThe 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 CC bonds). The consumption of the Si–H and CC 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 CC 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.
Referência(s)