A green water-soluble polyester slurry synthesis using MW-assisted glycolysis of recycled PET byproducts to evaluate the sizing performance

The escalating environmental burden of polyethylene terephthalate (PET) waste necessitates advanced chemical recycling strategies that combine efficient depolymerization with the direct upcycling of recovered monomers into value-added functional materials. Herein, an eco-efficient microwave (MW)-assisted glycolysis strategy catalyzed by lithium hydroxide (1.2 wt%) was developed to achieve rapid, near-complete depolymerization of waste PET under mild conditions (500 W, 10 min), yielding bis(2-hydroxyethyl) terephthalate (BHET) with a yield of 64.4% and a purity of 95.2%. The synergistic effect of volumetric microwave heating and base-catalyzed transesterification accelerates ester bond cleavage and uniform chain scission while suppressing further degradations. Following solvent extraction and recrystallization, the crude glycolysis products were used directly in a subsequent polycondensation with sodium dimethyl 5-sulfoisophthalate to synthesize a water-soluble polyester (WSP) slurry, thereby reducing energy-intensive purification. Applied as a sizing agent (6 wt% add-on) on staple polyester yarns, WSP significantly enhanced performance by reducing hairiness by 95% and improving abrasion resistance by 61%, while also increasing breaking strength and elongation. Although conventional polyvinyl alcohol (PVA) sizing offered slightly better wear resistance, WSP provided comparable mechanical reinforcement with drastically improved desizing efficiency (3.4%) owing to its intrinsic water dispersibility. This integrated recycling upcycling strategy establishes a closed-loop pathway for transforming PET waste into high-performance textile auxiliaries, accelerating polymer reutilization design, and providing a scalable route toward sustainable textile processing. • The depolymerization time is reduced to 600 s using a 1.2% LiOH catalyst, a 4:1 EG/PET ratio, and 500 W power. • BHET purity of 95.2% is achieved by this technique in glycolysis byproducts. • Glycolysis byproducts enhance the waterborne slurries' performance to reduce yarn hairiness. • The process yields superior desizing properties with excellent mechanical strengths.