Study of the thermal degradation of flame-retardant polyester GFRP using TGA and TG-FTIR-GC/MS

The thermal degradation behaviors of commercial flame-retardant unsaturated polyester glass fiber-reinforced plastic (polyester GFRP) containing aluminum trihydrate (ATH) were studied using thermogravimetric analysis and a combination of TG-Fourier transform infrared-gas chromatography/mass spectrometry (TG-FTIR-GC/MS). From the variation of derivative thermogravimetry curves, it is found that the degradation of polyester GFRP can be divided into two stages with the critical conversion rate of 0.35. Activation energies were calculated by Starink method, and then the kinetic triplet was further determined by Coats-Redfern method. The results show that the dehydration of ATH and breakage of ester linkages lead to the first major mass loss, and volatile products including H2O, dicyclopentadiene, benzaldehyde and dimethyl phthalate are generated. Consecutive reaction occurs in the second stage. The statistical rupture of polyester and polystyrene chains leads to the formation of toxic volatiles, especially styrene, α-methylstyrene, toluene, ethylbenzene, benzaldehyde, phenol and phthalic anhydride. Possible reaction mechanisms are discussed in order to explain the observed results. The experimental results could give guidance to the fire safety design of high-speed train and provide basic data for numerical simulation of fire accidents.