Selective depolymerization of PET to monomers from its waste blends and composites at ambient temperature

Abstract

Recycling of polyethylene terephthalate (PET), one of the largest varieties of synthetic polymers and the primary textile feedstock, presents a significant challenge when waste PET blends or composites are involved. Despite numerous efforts to address waste PET, it is difficult to achieve energy-efficient and selective depolymerization of PET through physical sorting systems or existing chemical means. Herein, we report a dichloromethane (DCM) and ethanol (EtOH) solvent system to selectively depolymerize PET into monomers while fully recover other mixture components. The complete depolymerization of PET and recovery of more than 99% of terephthalic acid (TPA) monomer can be achieved at room temperature within 30 min. After the reaction, TPA can be separated by simple filtration due to its insolubility in the solution. The filtrate can be reused for the recovery of PET. Molecular dynamics simulation shows that the high activity and selectivity is attributed to activating effect of DCM to PET ester groups, as well as pore-forming effect to promote PET interfacial mass transfer. Environmental energy impact and carbon emissions were evaluated and the results demonstrate the environmental friendliness of this method. This approach enables direct and efficient recycling of PET monomers from waste blends and composites, providing a viable solution to plastic and textile pollution.