Study on the Thermal Stability and Decomposition Kinetics of Polypropylene Glycol - Glycidyl Azide Polymer - Polypropylene Glycol (PPG-GAP-PPG) as a Novel Triblock Copolymer Binder

In this study, the novel energetic triblock copolymer of polypropylene glycolglycidyl azide polymerpolypropylene glycol (PPG-GAP-PPG) (Mn = 1419 g·mol–1) was synthesized by cationic ring-opening polymerization of propylene oxide using low molecular weight glycidyl azide polymer (GAP) (Mn = 1006 g·mol–1) as the initiator and boron trifluoride etherate (BF3·OEt2) as the catalyst. The synthesized GAP and triblock copolymer were characterized by Fourier-transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), and nuclear magnetic resonance spectroscopy (1H and 13C NMR). The thermal stability of the triblock copolymer PPG-GAP-PPG was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The DSC results showed that the glass transition temperature (Tg) of the triblock copolymer (Tg = −63 °C) was lower than that of neat low molecular weight GAP (Tg = −53 °C). Furthermore, the results indicated that this triblock copolymer is more stable than GAP. The influence of heating rate (10, 20, 30 and 40 °C·min−1) illustrated that increasing the heating rate results in an increase in the triblock copolymer’s decomposition temperature. Non-isothermal methods, proposed by ASTM E698, Flynn-Wall-Ozawa (FWO) and Kissinger, were used to calculate the kinetic parameters, such as activation energy and frequenc factor, for the thermal decomposition of the triblock copolymer PPG-GAP-PPG, using the DSC-DTG Central European Journal of Energetic Materials ISSN 1733-7178; e-ISSN 2353-1843 Copyright © 2020 Łukasiewicz Research Network – Institute of Industrial Organic Chemistry, Poland 263 Study on the Thermal Stability and Decomposition Kinetics... Copyright © 2020 Łukasiewicz Research Network – Institute of Industrial Organic Chemistry, Poland data. The activation energies calculated by the FWO and ASTM E698 methods were 124.610 and 126.13 kJ·mol–1, respectively.