Thermal degradation kinetics of semi-interpenetrating polymer network based on polyurethane and siloxane

A series of semi-interpenetrating polymer networks based on linear polyurethane and 1,3-bis(glycidyloxypropyl)-1,1,3,3-tetramethyldisiloxane, which was cross-linked with diethylenetriamine, were obtained. The samples have been submitted to thermal stability investigations at non-isothermal conditions in nitrogen. The kinetic parameters of the degradation process were determined both by isoconversional methods of Friedman and Ozawa-Flynn-Wall as well as by model fitting multivariate non-linear regression method. It was observed that the thermal stability of the semi-interpenetrating polymer networks depends on siloxane content. The best fit of the f(α) function with the experimental data was found for three-step degradation mechanism. Successive stages of thermal decomposition occurred by diffusion, phase-boundary and autocatalysis models, respectively.