The plastic wastes are continuously increasing, which approximately 8.3 billion tons of plastic wastes were generated in 2020. Additionally, the COVID-19 outbreak is promoting the growth of polyethylene terephthalate (PET) wastes. In this context, only 25% of plastic products are being recycled, of which the PET wastes are more feasible to be recycled. Mechanical recycling using an extrusion technique is considered one of the convenient recycling methods for post-consumer PET. This method has been received massive attention to overcome the PET wastes challenges in terms of feasibility, safety, and affordability. To this end, various mechanical recycling methods have been studied to improve the recycled PET (rPET) properties and close the loop based on the bottle-to-bottle (BtoB) approach. However, mechanical recycling using extruding method leads to a reduction in the rPET performance owing to the chain scission induced by thermal decomposition and hydrolysis. Therefore, the intrinsic viscosity (IV), mechanical properties, and thermal properties of rPET are reduced. The addition of a chain extender (CE) is one of the feasible methods to improve rPET properties and mitigate the challenges of mechanical recycling. In this study, PET flakes were modified by reactive extrusion method using an epoxy-functional group CE (EFCE) to maintain rPET properties according to the BtoB approach. Different concentrations of EFCE were added to PET flakes during extruding at 255 ± 5 <sup>o</sup>C, followed by pelletizing the modified rPET. The IV, chemistry (FTIR and NMR), barrier properties, and mechanical properties of rPET were investigated to identify the reaction mechanism. Accordingly, the oxirane ring of EFCE was reacted with the rPET terminal group via a ring-opening reaction, thereby improving the performance of rPET. Additionally, the addition of EFCE to the rPET during reactive extrusion led to an increase in the IV and rPET properties based on ubbelohde viscometer. Moreover, the EFCE as an FDA-approved compound for food contact had an acceptable migration, which might not pose health hazards to consumers.

In-situ reactive extruding modification of post-consumer PET to determine safety and performance for food contact materials

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