This study deals with the thermal degradation of polyurethane (PU) and poly
urethane/expandable graphite (PU/EG) coatings. EG represents a new generati
on 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 affect
ed by the presence of EG. On the other hand, they have enabled the determin
ation of the temperatures which correspond to different steps of the develo
pment 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 simi
lar for PU and PU/EG and consists in a carbonaceous polyaromatic species. H
owever. the results have suggested that the char formed from PU/EG may cont
ained trapped free radicals. (C) 2001 Elsevier Science Ltd. All rights rese
rved.