Poly lactic acid (PLA) has been used as common bioplastics nowadays, but the difficulties of identifying waste bioplastics and traditional plastics resulting in the decrease of the recycling values. Therefore, this study is aimed to investigate the feasibility of recycling the mixture of waste PLA and polyethylene terephthalate (PET) by pyrolysis, to increase the benefits of recycling. The results will serve as references for competent authorities and recycling dealers. The waste PLA and PET were mixed with various ratios and analyzed after pretreatment, then the parametric experiments were conducted. The pyrolysis experiments were conducted based on the reaction parameters obtained from TGA experiments, then the dynamics analysis were conducted according to the results of TGA and pyrolysis. The results showed that the calorific values of PLA and PET were approximately 4361 and 5458 kcal/kg, respectively, and those of the mixtures were in between them. The combustibles of both PLA and PET were higher than 96%, and the ashes were lower than 3%. PLA and PET both contained mostly carbon and oxygen. The glass transition temperatures of PLA and PET were 341 and 352K and the melting temperatures were 430 and 524K, respectively. TGA results showed that the maximum decomposition temperatures of PLA and PET were approximately 628~653K and 709~731K, respectively. Pyrolysis results showed that the gas yield increased with increased ratio of PLA to PET while the solid and condensate yields increased with increased ratio of PET to PLA; the solid yield increased while the condensate and gas yields decreased with decreased heating rates. The trends of energy yields were consistent with those of the pyrolytic product yields. The dynamics results showed that the activation energy and frequency factor increased with increased ratio of PET to PLA. The results of characteristics revealed that the pyrolytic products are supposed to be environmentally friendly.

poly lactic acid, polyethylene terephthalate, pyrolysis, resource recycling