Studies on the mechanism of thermal decomposition of unsaturated polyester resins with reduced flammability

On the basis of experimental results the kinetic dependencies describing the process of thermal degradation of polyester compositions [modified with halogen free fire retardant (Sn/Zn system)] (Figs. 11-13) as well as the mechanism of the process have been characterized. Thermogravimetric methods (TG, Figs. 1-4 and 8-10) including TG coupled either with Fourier transformation infrared spectroscopy (TG-FT-IR, Figs. 6-7) or with mass spectrometry (TG-MS) have been used in the investigations. It has been found that modification of polyesters using Sn/Zn system causes significant limitation of CO2 evolution and moderation of the combustion process because of slowing down the flame propagation as a result of modifier action. It has been established that stabilizing effect of fire retardant is a result of surface spherical barrier formation, which blocks the heat flow from the decomposition zone to the inner layers of a substance. A mechanism of polyester resins thermal stabilization using Sn/Zn system has been proposed.