A closed-loop process design for recycling expanded polystyrene waste by dissolution and polymerization

Abstract This study investigated recycling of expanded polystyrene (EPS) waste in a closed-loop design using the dissolution technique. The objective is to dissolve a maximum rate of EPS waste in styrene (its monomer), followed by suspension polymerization of this solution to incorporate the monomer (the solvent) in the polymer chain to avoid the need to separate the polymer and the solvent. The study evaluated the best operating conditions for these procedures, which resulted in 92% g·g−1 of particles at the appropriate size for expansion (425–1400 μm). Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were conducted to determine the chemical, thermal and rheological properties of the recycled polymers and to compare them with standard polymer, demonstrating that the recycled material kept its chemical, thermal, and rheological properties. This novel closed-loop technology has strong potential to produce recycled EPS with good properties and, if well established, will allow EPS recycling without the formation of secondary waste, in keeping with the principles of sustainable development and circular economy. A brief analysis of this process revealed a strong reduction in environmental impacts and suggests its economic viability, considering the demand for and market value of EPS and the investment required to produce it in a recycling process that could be amortized in a short period.