Ng Kok Wei Joseph, Lim Jacob Song Kiat, Gupta Nupur, Dong Bing Xue, Hu Chun-Po, Hu Jingdan, Hu Xiao Matthew
School of Material Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore, Singapore.
Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553, Singapore, Singapore.
Commun Chem. 2023 Jul 27;6(1):158. doi: 10.1038/s42004-023-00949-8.
Chemical depolymerization has been identified as a promising approach towards recycling of plastic waste. However, complete depolymerization may be energy intensive with complications in purification. In this work, we have demonstrated upcycling of mixed plastic waste comprising a mixture of polyester, polyamide, and polyurethane through a reprocessable vitrimer of the depolymerized oligomers. Using poly(ethylene terephthalate) (PET) as a model polymer, we first demonstrated partial controlled depolymerization, using glycerol as a cleaving agent, to obtain branched PET oligomers. Recovered PET (RPET) oligomer was then used as a feedstock to produce a crosslinked yet reprocessable vitrimer (vRPET) despite having a wide molecular weight distribution using a solventless melt processing approach. Crosslinking and dynamic interactions were observed through rheology and dynamic mechanical analysis (DMA). Tensile mechanical studies showed no noticeable decrease in mechanical strength over multiple repeated melt processing cycles. Consequently, we have clearly demonstrated the applicability of the above method to upcycle mixed plastic wastes into vitrimers and reprocessable composites. This work also afforded insights into a potentially viable alternative route for utilization of depolymerized plastic/mixed plastic waste into crosslinked vitrimer resins manifesting excellent mechanical strength, while remaining reprocessable/ recyclable for cyclical lifetime use.
化学解聚已被视为一种回收塑料废料的前景广阔的方法。然而，完全解聚可能能耗巨大，且提纯过程复杂。在这项工作中，我们通过解聚低聚物制成的可再加工的玻璃态高聚物，展示了将包含聚酯、聚酰胺和聚氨酯混合物的混合塑料废料升级再造的过程。以聚对苯二甲酸乙二酯（PET）作为模型聚合物，我们首先使用甘油作为裂解剂，展示了部分可控解聚，以获得支化PET低聚物。尽管回收的PET（RPET）低聚物分子量分布较宽，但随后它被用作原料，通过无溶剂熔融加工方法制备出一种交联但可再加工的玻璃态高聚物（vRPET）。通过流变学和动态力学分析（DMA）观察到了交联和动态相互作用。拉伸力学研究表明，在多个重复的熔融加工循环中，机械强度没有明显下降。因此，我们清楚地证明了上述方法可将混合塑料废料升级再造为玻璃态高聚物和可再加工复合材料。这项工作还为利用解聚塑料/混合塑料废料制备具有优异机械强度、同时可再加工/可回收用于循环使用寿命的交联玻璃态高聚物树脂提供了一条潜在可行的替代途径。
