A strategy to enhance recyclability of degradable block copolymers by introducing low-temperature formability

Abstract

Most thermoplastics are processed by melt-molding, which consumes energy and often results in thermal degradation of polymers and reduction of recycling opportunities. A potential solution is to introduce low-temperature formability in polymeric materials. Degradable block copolymers composed of poly(trimethylene carbonate) and polylactide are derived from renewables and processable at temperatures as low as ambient temperature through the application of pressure, thereby suppressing thermal degradation during processing and keeping the mechanical properties unchanged. An upper order-to-disorder transition phase behavior for the block copolymers can be predicted by the compressible regular solution (CRS) model. The block copolymers undergo a phase transition from an ordered (solid) state to a disordered (melt/solid) state by pressurizing to show fluidity. The melt/solid state is then reversibly solidified by removing the applied pressure. The low-temperature formability is dependent on the composition and molecular weight of the block copolymers. The “pressure plastics” substantially reduce energy consumption during processing with mitigating CO₂ emissions and enhancing recyclability. The elastomeric properties obtained allow the bock copolymers to be alternative to petroleum-based thermoplastic elastomers, such as polyethylene. In addition, the degradable nature reduces environmental impact even though escaping the collection system of the end-of-life plastics.