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Physicochemical properties and kinetic analysis for some fluoropolymers by differential scanning calorimetry
Poly(vinylidene fluoride–chlorotrifluoroethylene) (poly(VDF–CTFE)) copolymer is a kind of versatile fluoropolymers that can be used as binder for polymer-bonded explosives (PBXs) application. In this work, some of fluoropolymers consisting of VDF and CTFE units such as fluororubber SKF 32, fluoroplastic F-32L, fluoroelastomer KeL-F, fluoroplastic FK 800 and poly(VDF–CTFE) (abbreviated as SKF 32, F-32L, KeL-F, FK 800 and FKM, respectively) synthesized in-house have been characterized their physicochemical properties by means of gas pycnometer, scanning electron microscope (SEM), energy dispersive X-ray (EDX), organic elemental analyzer, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and thermogravimetry (TG). Glass transition temperature, melting point and crystallinity were measured by differential scanning calorimetry (DSC) method. Thermal stability and thermal degradation kinetics were studied using a temperature at the maximum reaction rate (peak) methods, i.e. Ozawa, Kissinger, Starink and Tang from DSC data obtained at four heating rates of 5, 10, 20 and 30 °C min−1 under nitrogen atmosphere and thermal stability from TG. The activation energy values calculated by Tang method for the thermal degradation of SKF 32, F-32L, KeL-F, FK 800 and FKM were obtained around 212.8, 204.9, 218.7, 238.8 and 245.5 kJ mol−1, respectively. These values of the activation energy are in good agreement and consistent with those Ozawa, Kissinger and Starink methods used for kinetic analysis. The thermodynamic parameters such as the activation free energy ΔG≠, activation enthalpy ΔH≠, and activation entropy ΔS≠ were also determined and discussed.
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