Poly(2-hexyne) is a substituted polyacetylene tractable into strong, thin membrane in spite of its relative instability, which can be overcome by using a suitable antioxidant. The evolution of chain scission with time for the thermo-oxidative degradation of poly(2-hexyne) in air was reported recently by the authors. Here, kinetic parameters of chain scission are estimated and influence of the activation energy of weight loss on the relationship between the chain scission and the weight loss is investigated. The study was carried out with samples of different molecular weight as well as in the presence of N-phenyl-alpha-naphthylamine as an antioxidant agent. All of these variables are related to the stability of poly(2-hexyne) films, characterized by the onset temperatures at which 0.5% weight loss and a critical. number of chain scission occur.