A facile and environmental friendly approach for recycling waste polystyrene foam

Polystyrene (PS), as a widely used plastic product, especially polystyrene foam (PSF), will permanently pollute the environment after consumption, the vast volume restricts its recycling and reuse. In this work, a novel environmentally friendly and sustainable approach is used to recycle waste PSF via near-critical water (NCW) method. Under NCW condition (185 ± 10℃, 1–1.5 MPa), the morphology of waste PSF changes to viscous state, returns to glassy state with subsequent temperature decrease, before finally recycling. The basic attributes of the recovered PS beads such as, chemical structure and thermal stability almost no change, which demonstrated the NCW method was feasible. This work proposes a new idea for recycling more pure PS, use water as the reaction medium reducing the use of organic solvent to protect environment, and reducing the CO₂ emission of the PS traditional synthetic pathway, which effectively alleviating the consumption of non-renewable resources and has potential to be sustainable recycled, reused of solid waste resource and applied on a large scale.