Thermal Decomposition and a Kinetic Study of Poly(Para-Substituted Styrene)s

Abstract

The thermal decompositions of polystyrene (PS), poly(p-methyl styrene) (PMS), poly(p-bromo styrene) (PBrS), and poly(p-chloro styrene) (PClS) were investigated through thermogravimetric analysis (TGA). For this aim, Flynn-Wall-Ozawa method was applied to derivative thermogravimetric (DTG) curves. Continuous distribution kinetics was employed with a stoichiometric kernel to determine the rate coefficients for decomposition reactions. TGA data for the polymers were investigated by nonlinear fitting procedures that yielded activation energies and frequency factors for the combined chemical reactions. The reaction order values of PS derivatives are just about 1 in the nonisothermal decomposition process. Ea values for PS, PMS, and PClS increase with % conversion individually as they decrease in the order of PS/PMS/PClS which is consistent with the molecular weight increase. On the other hand, PBrS has the highest activation energy. Also its activation energy decreases with the % conversion. Thus it is suggested that PBrS degrades with somehow different mechanism.