废旧聚酯扩链剂增黏反应条件优化及再生聚酯制备OA

Polyethylene terephthalate(PET),a semi-crystalline thermoplastic polyester renowned for its exceptional overall performance,exhibits superior physicochemical properties including high mechanical strength,excellent chemical resistance(particularly to acids,alkalis,and organic solvents),optical transparency,and low-cost processability.It has consequently become a cornerstone engineering plastic,finding widespread applications in food packaging(accounting for over 70%of global beverage containers),electrical insulation,textile fibers(representing more than 60%of polyester),automotive lightweight components,and biomedical devices. However,the high stability of the benzene ring structure and the dense crystalline regions within its molecular chain impart extreme chemical inertness,resulting in a degradation period of 300-500 years in the natural environment.Among the annual global production of over 20 million tons of PET waste,only about 30%is effectively recycled.The remainder enters landfills or is incinerated,contributing to persistent microplastic pollution and posing a severe threat to ecosystems.There is an urgent need for efficient polyester recycling(r-PET)to facilitate the transition towards a circular economy.The critical bottleneck in current r-PET recycling lies in the triple degradation mechanisms during multiple processing cycles:thermal degradation(ester bond scission generating carboxyl end groups during melt processing),hydrolysis(water residue catalyzing ester bond cleavage),and thermo-oxidative degradation(radical attack on the molecular chains).These processes lead to a decrease in molecular weight,a significant reduction in intrinsic viscosity(IV),and a 20%-40%loss in mechanical properties,severely restricting high-value recycling applications.Among mainstream recycling technologies,mechanical recycling relies on physical sorting-washing-melt extrusion-pelletizing/spinning.While operationally straightforward,it faces challenges such as high impurity content and irreversible IV drop,limiting its use primarily to low-end fiber production.Chemical recycling,involving depolymerization,monomer purification,and repolymerization(e.g.,methanolysis,glycolysis),can produce high-purity r-PET.However,it encounters economic challenges including high reaction temperatures,expensive catalysts,and substantial equipment investments. To address the aforementioned technical bottlenecks,this study employs an antioxidant-chain extension dual-functional synergistic system,achieving chain extension,viscosity enhancement,and high-value recycling of r-PET through a gradient optimization of multi-component additives.Initially,a blend of hindered phenol primary antioxidant 1010 and phosphite secondary antioxidant 168 is used to enhance free radical capture efficiency and effectively block degradation pathways.Subsequently,multi-functional chain extenders 4468,pyromellitic dianhydride(PMDA),and JW-AG are introduced to synergistically repair the broken molecular network,establishing a gradient optimization mechanism.By carefully controlling the addition sequence,temperature window,and concentration gradient of the additives,competitive consumption of functional groups is avoided,resulting in a positive synergy between antioxidant and chain extension efficacy.This approach successfully restores the IV value of r-PET to approximately 0.85 dL/g with a high retention rate of mechanical properties,providing a technically feasible and economically viable solution for the high-value recycling of r-PET.