Preparation and Degradation of Waste Polycarbonate-Derived Epoxy Thermosets and Composites
Ren-Yu Yeh, Kamani Sudhir K. Reddy, Yi‐Chun Chen, Meng-Wei Wang, Hou-Chien Chang, Mahdi M. Abu‐Omar, Ching Hsuan Lin
Abstract
We report a robust, 100% atom-efficiency strategy for preparing waste polycarbonate (WPC)-derived epoxy resin. To demonstrate the preparation process, we perform a pyridine-catalyzed model reaction between diphenyl carbonate (DPC) and diglycidyl ether of bisphenol A (DGEBA) in a molar ratio of 1:2. After epoxy-equivalent titration and two-dimensional nuclear magnetic resonance (2D-NMR) analysis, we confirm that the product is bis(1-(4-(2-(4-(oxiran-2-ylmethoxy)phenyl)propan-2-yl)phenoxy)-3-phenoxypropan-2-yl) carbonate (DPC-EP2). Based on the model reaction, three WPC-based epoxy resins (WPC-EPX, X = 2, 3, and 4) were prepared by the reaction of WPC with DGEBA in a molar ratio of 1:2, 1:3, and 1:4 in the presence of pyridine. The WPC-EPX epoxy resins were cured with WPC, phenol novolac (PN), diamino diphenylmethane (DDM), and dicyandiamide (DICY). The mechanical and thermal properties of the thermosets were discussed. We also prepared epoxy/carbon fiber composites and investigated the degradation of epoxy thermosets and the recycling of the carbon fiber. When the WPC-EP2 epoxy resin was cured with WPC, it can be successfully degraded to a phenoxy resin and 1,3-dihyexylurea through a catalyst-free aminolysis process. Undamaged carbon fibers have been recycled, according to the scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) and tensile stress–strain data. The transformation of WPC to WPC-EPX, the aminolysis of WPC-EP2/WPC to a phenoxy resin and 1,3-dihexylurea, and the recycling of carbon fiber in the composite have been successfully demonstrated. Therefore, we believe that this work contributes greatly to the field of “sustainable approaches in waste utilization.”