Thermal field-flow fractionation and gas chromatography - mass spectrometry in determination of decomposition products of expandable polystyrene after reactions in pressurized hot water and supercritical water

Nonbiodegradable polymers are an environmental concern, and various techniques have been developed to recycle and reuse them. Pressurized hot water, or supercritical water, is an interesting alternative as a reaction medium for depolymerisation, since water is a readily available "green" solvent and its physicochemical properties can be widely adjusted in the vicinity of the critical point. In the present study, various reaction conditions were applied to obtain as high styrene monomer yields as possible in the decomposition of industrial expandable polystyrene (EPS) in a pressurized, high-temperature aqueous medium. Other main reaction products were of interests as well. Thermal field-flow fractionation (ThFFF) was used after the degradation of EPS to check for possible high molar mass products. As a whole, the analytical techniques (GC-MS and ThFFF) employed in the characterization of EPS degradation in a pressurized, high-temperature medium complemented each other well and showed good performance.