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 investigate d 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 pr ovides 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 a ccepted. When all data obtained at the different heating rates studied were correlated, the single first-order reaction model provides a ver y poor correlation, whereas a model involving the formation of an inte rmediate yields very satisfactory results. With regard to EVA, a kinet ic model of this type also proved very convenient to represent the exp erimental data. As in the case of PE (Ref. 1) the surface of the sampl e holder has a remarkable effect on the kinetics of decomposition.