Thermal decomposition kinetics of poly(3,3′-bisazidomethyl oxetane-3-azidomethyl-3′-methyl oxetane)

Abstract

Poly(3,3′-bisazidomethyl oxetane-3-azidomethyl-3′-methyl oxetane) [P(BAMO/AMMO)] energetic thermoplastic elastomer (ETPE) is one of the most promising binders for the propellant and explosive formulations. It is synthesized with different content of hard segment and molar ratio of PBAMO and PAMMO. The results of mechanical test show that with higher content of hard segment and larger content of PBAMO, the ETPEs obtain higher tensile strength and lower breaking elongation. The thermal kinetics of the first decomposition stage of P(BAMO/AMMO) is investigated and the calculated apparent activation energy (E _a) is about 169 kJ mol⁻¹ by multi-heating rate method. In the single-heating rate study, f(α) = 1 − α is found to be the most probable mechanism function. Kinetic compensation effects are studied for the validation of the most probable mechanism function, and the results show that f(α) = 1 − α is quite suitable at a lower extent of conversion (α), but $f(\alpha ) = \frac{2}{3}\left( {1 - a} \right)\left[ { - { \ln }\left( {1 - a} \right)} \right]^{{ - \frac{1}{2}}}$ is more fit when α is larger.

Graphical Abstract

P(BAMO/AMMO) ETPE was prepared, and the thermal decomposition kinetic of the first decomposition stage (mainly the thermal decomposition of –N₃ group) was investigated. f(α) = 1 − α was a fitting mechanism function at a lower α, and $f(\alpha ) = \frac{2}{3}(1 - a)[ - \ln (1 - a)]^{{ - \frac{1}{2}}}$ was more suitable when α was higher.