Thermal degradation of polyurethane and polyurethane/expandable graphite coatings

Abstract

This study deals with the thermal degradation of polyurethane (PU) and polyurethane/expandable graphite (PU/EG) coatings. EG represents a new generation of intumescent additives which provides good fire retardancy to various materials and in particular to PU. The thermal analyses have shown that the thermo-oxidative degradation as well as the pyrolysis of PU are not affected by the presence of EG. On the other hand, they have enabled the determination of the temperatures which correspond to different steps of the development of the intumescence : formation, stabilisation and degradation of the intumescent shield. Spectroscopic analysis of the residues resulting from each of these steps has demonstrated that the structure of the char is similar for PU and PU/EG and consists in a carbonaceous polyaromatic species. However, the results have suggested that the char formed from PU/EG may contained trapped free radicals.