Closed-loop chemical recycling offers a promising solution to the end-of-life challenges of plastic waste. However, efficiently cleaving bonds to generate value-added products and develop chemically recyclable polymers remains a considerable challenge. We have developed a closed-loop upcycling strategy that depolymerizes poly(ethylene terephthalate) (PET) into bis(2-hydroxyethyl) terephthalate (BHET), followed by polycondensation to produce recycled PET (rPET). A series of xMn/Zn (x = 0, 0.5, 1, 2) catalysts, where x represents the molar ratio of Mn and Zn, were synthesized and employed to depolymerize PET plastic into the BHET monomer. The efficient PET glycolysis approach, utilizing the high surface area and weak acid sites of the 1Mn/Zn catalyst, achieved complete depolymerization of PET plastic with a BHET yield of 93.6 %. The recovered monomers can be utilized to remanufacture rPET, which exhibits competitive molecular weight, thermal stability, and rheological properties. The energy efficiency and techno-economic feasibility of the strategy for recycling PET waste plastic were assessed by constructing a lab-scale 5.0 g-grade process and simulating a 1-ton-grade process. This work introduces a closed-loop “PET-BHET-rPET” process, addressing end-of-use challenges, offering a cost-effective method, and providing a sustainable solution for upcycling plastic waste.
This study investigates the sustainable valorization of recycled polyethylene terephthalate (rPET) fibers through dopamine surface modification for enhanced 3D printed concrete (3DPC). Comprehensive tests on flowability, rheology, buildability, and mechanical anisotropy were conducted to assess the impacts of various MPET fiber content (0–0.5 vol%). The results showed that 0.5 vol% MPET fibers significantly increased dynamic yield stress and plastic viscosity by 247.6 % and 200.0 %, respectively, compared to the control group (P-0), while moderately reducing flowability. The 0.3 vol% content was found to be optimal, enhancing maximum printing heights in hollow cylindrical and rectangular structures by 114.8 % and 130 %, respectively, compared to the control. At this content, the 30-minute early compressive strength reached 66.0 MPa. Quantitative analysis revealed a strong correlation (R² > 0.94) between early strength development parameters and buildability performance, with rate of strength gain exerting greater influence than initial strength. Mechanical anisotropy tests showed that MPET fibers significantly enhanced the flexural strength of 3DPC in the Z-direction of printing. Scanning electron microscopy (SEM) analysis confirmed that dopamine modification significantly enhanced the fiber-matrix interface bonding. This research applies modified recycled PET fibers to enhance 3DPC performance while contributing to sustainability efforts in the construction sector, supporting approaches that integrate material recycling with technical innovation.
危险品化学品经营许可证（带存储）