Synthesis, thermal stability and kinetic decomposition of triblock copolymer polypropylene glycol–poly glycidyl nitrate–polypropylene glycol (PPG–PGN–PPG)

An energetic triblock copolymer PPG–PGN–PPG (M_n = 1886 g mol⁻¹) was synthesized for the first time by cationic ring-opening polymerization of propylene oxide with low molecular weight poly glycidyl nitrate (PGN) (M_n = 1061 g mol⁻¹) as a macroinitiator, in the presence of boron trifluoride etherate (BF₃·OEt₂) as the catalyst. The product obtained in high yield was characterized by FTIR, gel permeation chromatography and 1H and 13C NMR spectroscopy. The thermal properties of the triblock copolymer were characterized by differential scanning calorimeter (DSC). The result approved that the glass transition temperature of the triblock copolymer (T_g = − 58 °C) is lower than PGN (T_g = − 35 °C); also, it was more stable than that of PGN. The effect of heating rates (10, 20, 30 and 40 °C min⁻¹) on the decomposition of the copolymer was evaluated. The decomposition temperature of this compound increased as the heating rate increased. The kinetic parameters such as activation energy and frequency factor for the thermal decomposition of the triblock copolymer were obtained from the DSC and DTG data by non-isothermal methods proposed by the ASTM E696, Flynn–Wall–Ozawa (FWO) and Kissinger methods. The values by the FWO method are in good agreement with ASTM and Kissinger methods.