期刊
THERMOCHIMICA ACTA
卷 724, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.tca.2023.179492
关键词
Phthalonitrile; Thermal degradation; Isoconversional methods; Model -based kinetics; Multiple -step kinetics; Thermogravimetric analysis
The thermal oxidation decomposition process of phthalonitrile resins, post-cured at different temperatures, was investigated. The degradation process was found to be a complex four-stage process. The analysis showed that the first stage is an nth order reaction with autocatalysis. The phthalonitrile resin post-cured at 603 K exhibited better thermal stability compared to resins post-cured at higher temperatures.
The process of thermal oxidation decomposition of phthalonitrile resins which had been post-cured at various temperatures (603 K, 623 K and 648 K) was studied using dynamic and isothermal measurement modes. It was shown that the degradation process is a complex branched four-stage process. We have concluded that the first stage is an nth order reaction with autocatalysis. The second stage is described with the expanded Prout-Tompkins equation which corresponds to an autocatalytic solid-state reaction caused by the formation of im-perfections at the reaction surface. The third and fourth stages are also reactions of the nth order. The phtha-lonitrile resin post-cured at 603 K exhibited better thermal stability than the resins post-cured at 623 K and 648 K based on the activation energies of the 1st stage - 132 kJ/mol, 104 kJ/mol, and 106 kJ/mol respectively. These data were confirmed by comparable experimental activation energy values (111 kJ/mol, 87 kJ/mol, 86 kJ/mol respectively) and changes in mass loss and flexural strength values determined during long-term thermal aging in the temperature range of 553-623 K. It was shown that the phthalonitrile resin post-cured at 603 K with the initial flexural strength of 107 MPa is suitable for long-term application at temperatures up to 573 K.
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