Co-Pyrolysis Study of Polylactic Acid and Polyethylene Terephthalate Plastic Wastes

Separating plastics made of polyactic acid (PLA) and polyethylene terephthalate (PET) can be difficult; consequently, their recycling values are affected. The purpose of this study is to investigate the feasibility of recycling mixed PLA and PET wastes by co-pyrolysis. Specimens prepared from different ratios of preprocessed PLA and PET wastes were subjected to relevant property studies followed by thermogravimetric (TG) and reaction kinetic analyses. Subsequently, pyrolytic studies were conducted based on the obtained TG reaction conditions to investigate energy yields of pyrolytic reactions. Results indicated that the HHV of PLA and PET were approximately 18.26 and 22.85 MJ/kg, respectively and those of the mixtures were between these two values. Each specimen has a combustible portion of greater than 96% and a maximum decomposition temperature between 618K and 736K. Greater PET ratios were found to result in higher activation energies and pre-exponential factors. Additionally, PLA ratios were positively correlated to the mass yield of gaseous products, whereas PET ratios were positively correlated to the yields of solid and condensation products. Unless energy yield is a major concern, co-pyrolysing PLA and PET wastes may avoid the need to separate PLA and PET and may effectively reduce the volume of plastic wastes.