KINETICS OF THE PYROLYSIS OF HIGH-DENSITY POLYETHYLENE, LOW-DENSITY POLYETHYLENE, STYROFOAM AND THEIR BLENDS

Abstract

The pyrolysis characteristics of High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), Styrofoam (STF), and their blends were investigated to compare the process of the pure components with those of the blends. Thermogravimetric analysis (TGA) was employed to monitor the mass loss of the plastic samples during heating, providing critical insights into their thermal degradation behaviour. The pyrolysis kinetics were further examined using a multi-step integral method to determine the reactivities and activation energies of the materials. The results revealed that the pyrolysis processes of individual plastics could be characterized by a single reaction in the main decomposition zone. In contrast, the pyrolysis of binary (LDPE-HDPE, LDPE-STF, HDPE-STF) and tertiary blends (LDPE-HDPE-STF) exhibited two and three distinct reactions, respectively. Consequently, the decomposition of pure plastics follows a one-step mechanism, while the blends undergo multi-step mechanisms. Plastic pyrolysis is a crucial method for converting waste plastics into fuel-like substances. Hence, the term "fuels" highlights the potential of the resulting pyrolyzed products to serve as alternative energy sources. The results also showed variations in peak temperatures and decomposition intensities across different blends, significantly influencing the individual plastic materials' reactivities and activation energies. The activation energies for LDPE, HDPE, and STF ranged from 126.22 to 134.52 kJ/mol, while those for the blends were between 129.12 and 299.99 kJ/mol. Determining reactivities and activation energies is essential for understanding the efficiency and energy requirements of the pyrolysis process, helping optimize conditions for maximum fuel yield.