KINETIC-STUDY OF THE THERMAL-DECOMPOSITION OF POLYSTYRENE AND POLYETHYLENE-VINYL ACETATE GRAFT-COPOLYMERS BY THERMOGRAVIMETRIC ANALYSIS

The thermal decomposition behaviour of PS and EVA has been investigated by dynamic thermogravimetric analysis. Different kinetic models have been applied to correlate simultaneously the experimental weight loss data obtained at different heating rates. A single first-order fit provides a good correlation of the data obtained at any heating rate for PS, but a variation of the parameters with the heating rate must be accepted. When all data obtained at the different heating rates studied were correlated, the single first-order reaction model provides a very poor correlation, whereas a model involving the formation of an intermediate yields very satisfactory results. With regard to EVA, a kinetic model of this type also proved very convenient to represent the experimental data. As in the case of PE (Ref. 1) the surface of the sample holder has a remarkable effect on the kinetics of decomposition.