Glycidyl Carbamate Resins Synthesized through a Nonphosgene Route by Amidine-Based Superbases Using Recycled Polycarbonate

In this study, a ring-opening reaction of epoxide groups toward phenolic was proposed for obtaining glycidyl carbamate resins (GC resins) derived from waste polycarbonate (wPC) products, such as waste bottles. The wPC was first granulated, decolorized, and filtered, leading to wPC solution in anisole (yield = 98%). In the next step of the chemical recycling procedure, the wPC was fully converted into a raw material for producing GC resins. Through model reactions, a catalytically selective ring opening of epoxide groups toward phenol or carbamate groups was found. Therefore, to determine the appropriate reaction conditions such as reaction temperature, heating time, and catalytic conditions, differential scanning calorimetry was used to investigate the exothermic reactions. Initially, wPC was aminolyzed into hydroxyl-N,N′-diphenylene-isopropylidenyl biscarbamates as interim products, which were then subjected to ring opening of epoxide groups to produce diglycidyl-N,N′-diphenylene-isopropylidenyl biscarbamates (GC resins) in the presence of the amidine-based catalyst 1,5-diazabicyclo[4.3.0]non-5-ene. This approach provides not only a waste disposal solution, but also a nonphosgene route for the synthesis of carbamate. These GC resins were capable of self-curing to result in new polymer products with superior properties, such as high tensile strengths (>80 MPa) and large elongations at break (>200%), as measured in tensile tests.