From Zero to Hero: Polymer Upcycling through Transformation of Waste PET Thermoforms into Kevlar

Polyethylene terephthalate (PET) is a widely used plastic packaging material that is often discarded after use. Previous studies have used recovered terephthalic acid derivatives to produce poly(p-phenyleneterephthalamide) (PPTA), an expensive commodity scale polymer widely known by the trade name Kevlar. Here, PPTA is synthesized using carbon that is 100% recovered from waste PET. To do so, the monomer p-phenylenediamine (PPD) is obtained through two facile "one-pot" reactions: (1) ammonolysis of PET to yield terephthalamide and (2) conversion of terephthalamide to PPD through a Hofmann type of rearrangement. Following earlier works, hydrolysis of PET followed by chlorination provides the monomer, terephthaloyl chloride (TCl). PPTA is synthesized by reacting the monomers in a solution of n-methyl pyrrolidone and calcium chloride. The pathway is demonstrated using zero-valued waste "clamshell" PET, a material usually excluded from recycling streams. The material reuse results in a lifesaving polymer used by members of the military, police, and other first-responders. It is concluded that this pathway provides an economic means of recovering and reusing waste PET that can reduce dependence on nonrenewable resources and foster greater material circularity in the plastics industries.