Pyrolytic decomposition and model-free kinetics analysis of mixture of polypropylene (PP) and low-density polyethylene (LDPE)

Thermal decomposition behaviour of mixtures of polypropylene (PP) and low-density polyethylene (LDPE) with different weight ratios (20:80, 35:65, 50:50, 65:35, 80:20) is studied under non-isothermal conditions at five different heating rates. Presence of synergistic effect is observed for mixture samples with PP composition >40 wt.%. Formation of hydrocarbons (<C-6) and (C-6-C-10) fractions are the highest in case of (PP(65%) + LDPE(35%)). The nonlinear Vyazovkin model-free analysis is used to understand the variation of activation energy, E-alpha with conversion, alpha. For almost all the mixtures, initially E-alpha is a slow but increasing function of alpha and then becomes a very strong function of alpha towards the end of the decomposition phenomenon. E-alpha is much lower for the mixtures (PP(50%) + LDPE(50%)), (PP(65%) + LDPE(35%)) and (PP(80%) + LDPE(20%)). The plastic mixture PP:LDPE = 65%:35% is the most preferable one during pyrolysis due to its low activation energy and formation of significantly high amount of hydrocarbons of range (<= C-10). (C) 2008 Elsevier B.V. All rights reserved.