4. Conclusions
Comparing the results under two circumstances, the activation energy value E in N2 is almost twice times of that in air. It
is confirmed that the thermal degradation of XPS is much easier under air. The E value maintains an approximate constant
165 kJ/mol in N2, while it stabilizes around 90 kJ/mol in air.
XPS follows a two-stage and three-stage weight loss during the entire process under nitrogen and air, respectively. Some
small molecule products remaining in the materials or additives volatilize in the initial stage. Since the existence of oxygen,
the degradation reaction in air becomes more rapidly and violent with a complicated mechanism. The total heat release
reach up to 2107.97 J/g with only one apparent endothermic peak in N2.
On the basis of Py-GC-MS technique, it is demonstrated that depolymerization reaction predominate the thermal
degradation of XPS in helium and styrene monomers are the dominant volatile gases. Methylbenzene, α-methyl styrene,
dimer and some other oligmers of styrene are also detected.