Thermogravimetric evaluation of the kinetics of decomposition of polyolefin blends

The thermodegradative behavior of polypropylene (PP), of non-degraded and degraded high density polyethylene (HDPE) and their blends was studied, in order to analyze their thermal stability. Van-Krevelen (V-K), Coats-Redfern (C-R) and Horowitz-Metzger (H-M) integral methods as well as the Freeman-Carroll (F-C) differential approach were used to determine kinetic parameters. The activation energy (E-a) obtained for PP mixed with non-degraded HDPE (5 to 50%) is lower than the E-a corresponding to pure polymers and does not depend on the HDPE concentration. Blends of degraded materials show an approximate value of E-a of 200 kJ/mol for H-M, 160 KJ/mol for V-K and 150 KJ/mol for C-R, for mixtures with concentrations by weight of HDPE up to 20%, but this value decreases drastically with higher concentrations. (C) 1998 Elsevier Science Limited. All rights reserved.