Thermal decomposition study of carbon fiber-reinforced polyphenylene sulfide at high heating rates met under fire exposure

Performing pyrolysis studies on polymer matrix composites, at rates that match the elevation of temperature met during a fire exposure, is of primary interest for the aeronautics field. In this study, one aspect of the material response under flame is investigated, which is the thermal degradation of the polymer matrix. Thermogravimetric analyses (TGA), up to five hundred Kelvins per minute, are performed on polyphenylene sulfide (PPS) and carbon fiber-reinforced polyphenylene sulfide (CF/PPS), to mimic the heating rate conditions commonly met during a fire. The influence of the heating rate regarding the PPS decomposition signature is discussed from both the residual mass and the characteristic temperature corresponding to the maximum rate of degradation. Then, the PPS thermal decomposition features are compared with those of several thermoplastic polymers and thermoplastic–based composites. It is observed that PPS stands out when subjected to fast elevation of temperature. Indeed, its amount of «char», obtained after thermal degradation, increases with the heating rate. To investigate possible mechanistic causes behind this singular behavior, the influence of the heating rate on the degradation mechanisms occurring into PPS and CF/PPS is investigated. TGA coupled with Fourier transform infrared spectroscopy (FTIR) is used to obtain the decomposition products. The results plaid for the coexistence of two main degradation mechanisms, being the random chain–scission and the depolymerization. Nevertheless, when the heating rate increases, the random chain–scission seemingly becomes the predominant mechanism along the whole process. Graphical abstract: (Figure presented.)