New insights into typical biodegradable plastics in rapid pyrolysis: Kinetics, product evolution and transformation mechanism

Abstract

Biodegradable plastics (BP) have undergone rapid development in the field of replacing traditional packaging plastics. However, their recycling and disposal systems are unclear, and the standards are different, causing new environmental pollution. The rapid and appropriate disposal of BP has become a worthy direction of exploration. Here, rapid pyrolysis technology was used to explore the recycling of BP, and the product evolution and transformation mechanism of typical BP (BP1∼BP4) were analyzed. The results show that the main reaction stages of BP pyrolysis are concentrated at approximately 260∼450 °C. Most of the heat treatment stages of BP conform to the random nucleation and nuclear growth model An (n = 1.5, 2, 2.5. 3). The gaseous products of BP pyrolysis were mainly 1, 3-butadiene. The top four pyrolysis components are the same for the liquid products of BP1, BP2, and BP4, which are mainly benzoic acid (42.54%–44.67%). However, the proportion of polycyclic aromatic substances in the products of the BP3 pyrolysis solution was as high as 63.85%. For the transformation mechanism, BP containing polylactic acid (PLA) and polybutylene terephthalate-adipate (PBAT) is mainly composed of C–O bond fractures at the ester group and intramolecular hydrogen transfer to form a carboxyl group and CC. This study of BP pyrolysis provides an important scientific basis and theoretical reference for its rational and rapid treatment and product recovery and reuse.