Single-Fiber Visualization of Poly(ethylene terephthalate) during Alkaline Hydrolysis: Testing of Surface Reaction Model and Mechanism

Poly(ethylene terephthalate) (PET) is a primary category of waste plastics. Chemical depolymerization can transform waste PET into monomers for circularity. However, the heterogeneity of consumer PET products can affect the depolymerization uniformity. We characterize this variation by visualizing the alkaline hydrolysis of single PET fibers. We establish the distribution of depolymerization kinetics through image analysis, tracking individual PET fibers and their evolution. The distributions of the hydrolysis kinetics are reported, where the average rates were used to model the bulk PET weight loss. We further found that textile additives affected the hydrolysis kinetics, a finding we attribute to changes in the hydrolysis sites on the PET surface, which alter the activation barrier. We conclude that additives could be a source of hydrolysis variations, leading to nonuniform PET depolymerization in large-scale recycling reactors.