Upcycling of waste epoxy thermosets to robust polyurethane foams via an in situ degradation-foaming process. Issue 2 (April 2023) - Zhao, Xu
Abstract: High-efficiency and energy-saving conversion of epoxy thermosets into "three-high" (high value, high quality and high performance) products is highly desired from the viewpoints of both environmental protection and resource utilization. Here, we demonstrate a new strategy for mild degradation of epoxy thermosets and in situ preparation of polyurethane foam from degradation solutions. The degradation solution contains the unreacted solvent polyethylene glycol and polyol degradation products after alcoholysis, both of which can react with isocyanate to produce polyurethane. The use of an insoluble catalyst makes it possible to achieve in-situ foaming of the degradation solution, which realizes the direct and full utilization of degradation products. Owing to the rigid epoxy skeleton of the degradation products, the obtained rigid polyurethane foam exhibited high mechanical properties (∼170kPa), good thermal insulation performance (33–35 mWm −1 K −1 ), low water absorption (3–5%), regular pore structure and good thermal stability, thus can be a good candidate for building insulation materials. Graphical Abstract: ga1 Highlights: The self-precipitation of catalyst avoids complex separation and wash process. In situ foaming by using degradation solution directly. Upcycling of waste epoxy thermosets to robust polyurethane foams. Waste-based source of polyurethane foam with cleaner production.