Study on kinetic parameters and reaction mechanism of chlorinated polyvinyl chloride using thermogravimetry and peak-differentiating analyses

As a popular engineering thermoplastic material, chlorinated polyvinyl chloride (CPVC) has extensive utilization. However, CPVC may combust, cause fires and release hydrogen chloride, which is a hazard to humans, equipment and the environment. Thermal degradation is the initial stage of combustion and can provide gas fuel to support combustion. Consequently, thermal degradation knowledge is conducive to modeling flame spread, such as Fire Propagation Apparatus experiments, which should be further studied. Thermogravimetric analysis was performed under different heating rates in the air, which showed that CPVC was a multiple-step reaction. Then, peak-differentiating analysis was conducted by using the Gaussian function, and three sub-reactions (dehydrochlorination reaction, the evolution of chlorine-containing hydrocarbons and carbonaceous residue reaction) were obtained and possible reaction equations were proposed. Additionally, the kinetics parameters of three sub-reactions were calculated by model-free methods. It showed that activation energy was 127.99, 331.29 and 91.68 kJ/mol, respectively. Subsequently, the master plots method was utilized to acquire the reaction mechanisms of sub-reactions, which were all expressed as f(α) = (1 − α)n. Next, the Particle Swarm Optimization algorithm was used to optimize the 15 kinetic parameters. When a good agreement was obtained between optimized results and experimental data, optimized values were determined. Finally, thermodynamic parameters were estimated based on the optimized values.