Study on thermal aging properties of PBT energetic elastomer

Accelerated aging experiments of 3,3-bis(azidomethyl)oxetane (BAMO) and tetrahydrofuran (THF) copolymers (molar ratio 1 : 1, marked as PBT prepolymer) and PBT elastomer at elevated temperatures were performed to explore the aging mechanism of PBT energetic elastomer during long-term storage. The evolution of functional groups, plasticizer content, element chemical state and crosslinking density were studied by FT-IR, HPLC, XPS and swelling method, respectively. Results show that: (1) Oxidation of terminal hydroxyl, oxidative crosslinking between binder macromolecules, chain breaking of polymers and degradation of -CH2N3 occurred during the thermal aging of PBT prepolymer, and antioxidant (BHT) could effectively delay the thermal aging process of PBT prepolymer by absorbing the active oxidation substances. (2) The relative contents of -C=O showed a cubic function with time, and the relative contents of -NO2 and -N-3 changed linearly with time during the thermal aging of PBT elastomer. The relative contents of BDNPF and BDNPA declined linearly with time, and the thermal stability of BDNPF was better than that of BDNPA. (3) The thermal aging of PBT elastomer experienced three main reaction stages: degradation of carbamate, the oxidative crosslinking of molecular chain caused by the decomposition products of BDNPF/BDNPA, and chain breaking of the polymer system. In addition, a small amount of -CH2N3 decomposed throughout the whole aging process.