Alkaline hydrolysis of PVC-coated PET fibers for simultaneous recycling of PET and PVC

Abstract

Polyvinyl chloride (PVC)-coated poly(ethylene terephthalate) (PET) woven fibers are one of the hardest-to-recycle polymeric materials. Herein we investigate the possibility of recycling both PVC and PET through alkaline hydrolysis of PET. The coated woven fabrics were treated with NaOH, hydrolyzing the PET fibers into water-soluble sodium terephthalate, while the PVC could be removed by filtration. The PET fibers were completely hydrolyzed between 120 and 180 °C in the presence of 1 M NaOH solution, quantitatively yielding terephthalic acid. A minimum PVC dechlorination rate of 1% was simultaneously achieved at 120 °C. Furthermore, no alkaline hydrolysis of the plasticizer contained in the PVC, di(2-ethylhexyl)phthalate, was observed. Thus, the possibility of simultaneously recycling PET and PVC from PVC-coated woven fabrics was demonstrated. Kinetic analyses of PET hydrolysis and PVC dechlorination revealed that the simultaneously occurring reaction processes did not affect the progress of each other. Thus, the absence of interactions between PET, PVC, or their degradation products enables the design of a simplified recycling process without considering the interactions between the materials derived from coated woven fabrics.