A facile strategy to achieve polyurethane vitrimers from chemical recycling of poly(carbonate)

Abstract

Polyurethane vitrimers (PUVs) incorporating urethane reversion covalent adaptable networks are usually limited by the use of aliphatic alcohol for carbamate groups, resulting in high activation energy for bond exchange. In this study, PUVs bearing phenolic carbamate were demonstrated to overcome the low reactivity between phenol and isocyanate in the consumption of polymer wastes. First, poly(carbonate) (PC) was converted to a versatile intermediate mixture of hydroxyl N, N’-diphenylene-isopylidenyl biscarbamates (DP-biscarbamates). Unlike previously developed products with linear structures, the incorporation of a crosslinking agent, trimethylol propane with multiple functional groups would generate crosslinked structures in PUVs with improved mechanical properties. Due to the active sites provided by phenolic carbamate-containing DP-biscarbamate, the PUV products exhibit a gradual viscosity drop that follows the Arrhenius equation and corresponds to the feature of vitrimers with dissociative covalent adaptable networks. These products exhibit activation energies below 100 kJ/mol for topology rearrangement, facilitating the reprocessability for compression molding at mild temperatures of 120 °C. Overall, this study provides a new insight into an efficient material recycling process by the utilization of polymer waste.

Keywords

• Polycarbonate waste
• Chemical recycling
• Polyurethane vitrimers
• Thermoset
• Phenolic carbamate