Poly(methylhydrosiloxane) networks of different structure and content of Si-H groups: Physicochemical properties and transformation into silicon oxycarbide ceramics

In the work, poly(methylhydrosiloxane) was cross-linked by three vinylsiloxanes differing in molecular structure and functionality, i.e. linear difunctional (MMVi)-M-Vi, branched tetrafunctional Q(M-Vi)(4) and cyclic tetrafunctional D-4(Vi). The cross-linking process was conducted at three molar ratios of Si-H to Si-CH=CH2 groups in order to obtain different amounts of unreacted Si-H groups in the systems. As established by swelling measurements, the applied cross-linker and molar ratio of reactive groups show the influence on the average cross-linking densities of the studied systems. Conducted thermal investigations allowed to conclude that the amount of Si-H groups present in the system affects the number of decomposition steps of the studied networks. The results of thermal studies of the cross-linked samples were complemented by FTIR and XRD analyses of the residues formed after pyrolysis of the cross-linked products conducted at different temperatures in the range between 200 and 1000 degrees C in Ar atmosphere. The presence of the free carbon phase in the obtained silicon oxycarbide materials was confirmed by Raman spectroscopy. (C) 2017 Elsevier Ltd. All rights reserved.