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Commercial fluororubber SKF 32, fluoroplastic F-32L, fluoroelastomer Kel-F, fluoroplastic FK 800 (labeled as SKF 32, F-32L, Kel-F and FK 800) and an in-house prepared poly(vinylidene fluoride-chlorotrifluoroethylene) (FKM) copolymer were investigated in terms of their thermal degradation kinetics, reaction models and corresponding thermodynamic parameters. All samples underwent a single step thermal degradation using thermogravimetric analysis (TGA) at different heating rates under nitrogen atmosphere. The kinetic parameters were determined through the Kissinger method and three isoconversional methods; viz. the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink. The activation energies of the SKF 32, F-32L, Kel-F, FK 800 and FKM obtained using the Kissinger method were 206, 200, 185, 221 and 243 kJ mol‒1, respectively. The activation energy values for the degradation obtained using the KAS method were: 180–225 kJ mol−1 for SKF 32, 192–209 kJ mol−1 for F-32L, 163–185 kJ mol−1 for Kel-F, 213–227 kJ mol−1 for FK 800 and 187–269 kJ mol−1 for FKM with the extents of conversion (α) = 0.1–0.9. These values of the activation energies obtained from the KAS method were in good agreement with those obtained using the FWO and Starink methods. In addition, the appropriate degradation reaction models were determined by means of the Coats-Redfern and Criado methods. The thermodynamic parameters, such as activation Gibb free energy, ΔG*, activation enthalpy, ΔH*, and activation entropy, ΔS*, for formation of the activated complexes during the thermal degradation were also determined and discussed. The positive values of the Ea, ΔG*, ΔH*, and ΔS* for SKF 32, F-32L, FK 800 and FKM indicated a non-spontaneous process, while the positive values of the Ea, ΔG* and ΔH*, and negative value of ΔS* for Kel-F meant that the formation of the activated complex was accompanied by a smaller decrease of entropy than for the other polymers. [ABSTRACT FROM AUTHOR]

A compatibility of energetic compound with polymeric matrices is of prime importance in the pre-formulation stage for developing of new energetic composite formulations. In the present work, the compatibility of octahydro-l,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with polyether (PET) polyol (trade name SP-755)-based polyurethanes (PUs) containing different curatives such as 4,4ʹmethylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), and toluene diisocyanate (TDI) has been studied by using a differential scanning calorimetry method. The PET-based PUs were prepared by polymerization between PET polyol and different curatives, then these PUs were further mixed with HMX to study the compatibility and kinetic parameters. Results show that the compatibility and thermal stability are significantly influenced by the different curatives, and suggested thermals stability by thermal data follow the order for a mixture of HMX/SP-755/MDI > HMX/SP-755/TDI > HMX/SP-755/IPDI > HMX/SP-755/TMDI. The thermal degradation kinetics has also been investigated through non-isothermal conditions using the Kissinger and the isoconversional ASTM E689 kinetic methods. The finding shows that there was a significant variation in the apparent activation energy for a mixture of HMX/SP-755/MDI, HMX/SP-755/IPDI, HMX/SP-755/TMDI, and HMX/SP-755/TDI, which were 365.8, 257.7, 134.9, and 241.1 kJ mol−1, respectively. The apparent activation energies obtained from the Kissinger method at maximum peak temperature are in reasonable agreement and consistent with isoconversional ASTM E689 kinetic method. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, thermal degradation and degradation kinetic of a poly(vinylidene fluoride–chlorotrifluoroethylene) (poly(VDF–CFTE)) copolymers are investigated by thermogravimetry (TG) under non-isothermal conditions. Thermal degradation of poly(VDF–CFTE) copolymers namely FKM1, FKM2, FKM3 and FMK4 samples is carried out at different heating rate under nitrogen atmosphere. The activation energies of poly(VDF–CFTE) samples are calculated from Kissinger–Akahira–Sunose (KAS) and Friedman kinetic methods. To investigate the kinetic model of thermal degradation for poly(VDF–CTFE) copolymers, Criado method is employed. The results showed that the probable model for the degradation of poly(VDF–CTFE) copolymers agreed with a power law and diffusion (D 1) model. The activation energies of FKM1, FKM2, FKM3 and FKM4 samples are found to be 196, 197, 198 and 207kJmol−1, respectively. [Copyright &y& Elsevier]