Thermal redistribution reactions in crosslinked polysiloxanes

Abstract

The thermolysis under argon of various polysiloxane resins containing D, T, DH, or TH units was investigated using thermogravimetric analysis combined with mass spectroscopy (TG/MS analysis) and solid‐state 29Si‐NMR. Redistribution reactions involving the exchange of SiC/SiO bonds or SiH/SiO bonds were evidenced in addition to the exchange of SiO/SiO bonds reported to date. These reactions significantly modify the initial siloxane units and lead to an escape of volatile silanes or siloxanes. The exchange of SiH/SiO bonds takes place at lower temperatures (300°C) than the exchange of SiC/SiO bonds (500°C).

Preparation and structure of silicon oxycarbide glasses derived from polysiloxane precursors

“…We investigated the pyrolysis of cross-linked polysiloxanes containing various siloxane units, using 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR), and thermogravimetric analysis coupled with mass-spectrometry (TG/MS analysis) [10]. The thermal reactions involved may be divided in two classes:…”

Silicon-Based Polymer-Derived Ceramics: Synthesis Properties and Applications-A Review

“…The separation of free carbon 248,249 and the microstructural development of the SiCO ceramics were reported in different studies. 240,250 The influence of the free carbon phase on the electrical properties of oxycarbide glasses with and without fillers was studied by Engel 251 and Cordelair.…”

Investigation of the pyrolysis mechanisms of cellobiose in the presence of a polysiloxane

“…Si-O/Si-C redistribution reactions around silicon atoms account for this fact (Scheme 2). Redistribution reactions between Si-O and Si-C bonds have been previously studied by 29 Si NMR spectro- scopy in resins containing T or D + T units [9]. Their key role in the production of Si/C/O ceramics has recently been emphasized [10].…”

“…Concerning their behaviour at high temperature, many reports deal with their thermal degradation and it is known that redistribution mechanisms take place around silicon atoms [5][6][7][8]. Recently, the pyrolysis of polysiloxanes has drawn renewed attention as silicone resins have emerged as new Si/C/O-based ceramic precursors [9][10][11][12][13][14]. However, very little is known about the behaviour of polysiloxanes heated in the presence of cellulose [15][16][17].…”