Pyrolysis kinetics of pure and waste plastics by non-isothermal thermogravimetric analysis

• Main Author: Ma, Lin
• Other Authors: Wang Jing-Yuan
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/45192
• Institution: Nanyang Technological University

Two sets of Thermogravimetric Analysis (TGA) studies of the pyrolytic degradation of plastics were carried out in a non-isothermal manner. Both investigations were conducted at temperature ranging from 303K to 1173K in a nitrogen atmosphere. The first study assessed the thermal characteristics of pure polystyrene (PS), polypropylene (PP), and low density polyethylene (LDPE) at four different heating rates, β, 5, 10, 20, 50 K/min. Two different kinetic models, the Flynn-Wall-Ozawa method and the first order Coats-Redfern method, were adopted to calculate the kinetic parameters of the samples. Both methods showed that the pyrolysis of PS, PP and LDPE could be considered as a first order degradation process. However, the values of activation energy calculated based on the two methods were different. The first order Coats-Redfern method was concluded as the better kinetic model for this study, with activation energies of 267-292 kJ/mol for PS, 282-332 kJ/mol for PP, and 196-253 kJ/mol for LDPE at the four different heating rates. The second study analyzed the kinetics of thermal degradation of pure and waste PS, PP, and LDPE at a uniform heating rate of 10 K/min. The kinetic parameters calculated were based on the first order Coats Redfern method. Results indicated that the degradation of waste plastics followed first order reactions similar to their corresponding pure samples, whereas the kinetic parameters varied considerably due to the presence of different additives and impurities in the waste plastic samples.