Upcycling of Postconsumer PET Using Serinol: Green Preparation of a New Multifunctional Initiator for PLA

Chemical recycling is attracting more and more interest as it can transform a plastic scrap into a high-value material. This work shows that the aminolysis of postconsumer poly(ethyleneterephthalate) (PET) with serinol, a nontoxic and biosourced hydroxyamine, leads to a novel multifunctional initiator for poly(lactic acid) (PLA). The reaction was performed at 180°C, without the need of catalysts, and resulted in a substantially complete aminolysis of PET, selectively yielding the corresponding diamide of terephthalic acid (terephthalic acid serinol bis-amide, TASBA), together with ethylene glycol as the co-product. TASBA holds four hydroxy groups and was used as multifunctional initiator in the polymerization of lactide to PLA, with 0.1%, 0.5%, and 1% w/w of TASBA with respect to L-lactide. TASBA led to a multiarm PLA, whose molecular weight and thermal and rheological properties could be tuned with the amount of initiator. The lowest amount of initiator left substantially unaffected the molecular weight and led to higher melt viscosity and to lower crystallinity. Lower molecular weight and melt viscosity were obtained by increasing the amount of TASBA. This work therefore proposes a synergy between the most important polyesters, the most diffused PET and the compostable PLA.