Kinetic model for the pyrolysis of polysiloxane polymers to ceramic composites

A model describing the pyrolysis of an organo-silicate polymer (Blackglas polymer) to form a silicon oxycarbide glass was developed based on the known chemistry and architecture of the polysiloxane precursor. The objectives were to develop a plausible reaction pathway to explain the pyrolysis process, rate, and product spectrum, and to study the effect of various heating protocols on the pyrolysis process. The model successfully predicted the evolution rates of the major gases as a function of process temperature and the overall pressures reached during the process. The effects of various heating protocols on the outgassing kinetics were studied to develop an optimum protocol for a rapid pyrolysis process that gives a composite with desirable mechanical properties. Overall, the model appears to capture the essential characteristics of the process and is in good agreement with experimental results.