Collaborative Innovation Center for Eco-Friendly and Fire-Safety Polymeric Materials (MoE), State Key Laboratory of Polymer Materials Engineering, National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan), College of Chemistry, Sichuan University, Chengdu, 610064, P. R. China.
ChemSusChem. 2022 Feb 8;15(3):e202101607. doi: 10.1002/cssc.202101607. Epub 2021 Dec 29.
Plastic has now become a contradiction between civilization and pollution that human society has to resolve. The recycling of thermosetting plastics in waste plastics is a huge challenge since they are difficult to remold like thermoplastic plastics due to their high crosslinking density. Here, a new strategy was developed to achieve multicycling of anhydride-cured epoxy thermosets. The process consisted of mild and high-efficiency alcoholysis catalyzed by potassium phosphate/low-boiling alcohol system, and subsequent fast hydrolysis to obtain degradation products rich of carboxyl groups. The degradation products were reused as curing agent to prepare new anhydride-cured epoxy thermosets without sacrifice of high strength and stability. Moreover, the new epoxy thermosets could still be repeatedly recycled using the same protocol. The insolubility of potassium phosphate in ethanol at room temperature made the separation and reuse of the catalyst more convenient. The use of low-boiling alcohol not only allowed high-efficiency degradation but also enabled easy separation from the degradation products. The excellent degradation performance was attributed to the improved swelling of the thermoset and the increased solubility of potassium phosphate induced by small amounts of water in the alcohol. This research provides a recycling method that can reintegrate thermoset waste plastics into remodeling ones under the background of circular economy.
塑料现在已经成为人类社会必须解决的文明与污染之间的矛盾。热固性塑料在废塑料中的回收是一个巨大的挑战，因为它们由于交联密度高，像热塑性塑料一样难以重塑。在这里，开发了一种新的策略来实现酸酐固化环氧树脂热固性的多次循环利用。该过程包括由磷酸钾/低沸点醇体系催化的温和高效的醇解，以及随后的快速水解，以获得富含羧基的降解产物。降解产物被重新用作固化剂，以制备新的酸酐固化环氧树脂热固性塑料，而不会牺牲高强度和稳定性。此外，使用相同的方案，新的环氧树脂热固性塑料仍然可以重复回收利用。室温下磷酸钾在乙醇中的不溶性使催化剂的分离和再利用更加方便。使用低沸点醇不仅允许高效降解，而且还可以使醇解产物易于分离。优异的降解性能归因于少量水在醇中引起的热固性的溶胀增加和磷酸钾的溶解度增加。这项研究提供了一种回收方法，可以在循环经济的背景下将热固性废塑料重新整合到重塑塑料中。
