Extraction of various additives from polystyrene and their subsequent analysis

The extraction of fifteen polymer additives which are used as antioxidants, uv stabilizers, process lubes, flame retardants, and antistats from eight formulations of polystyrene is demonstrated with supercritical carbon dioxide and compared to traditional dissolution/precipitation extractions. The purpose of the study was two fold: 1) the development of a high performance liquid chromatography method(s) for the additives and 2) the determination of the viability of supercritical fluids for extraction of the additives from polystyrene. Nine of the additives were assayed via reversed phase liquid chromatography while, the remaining six additives could not be assayed in this manner. In order to develop an extraction method for the additives, the effects of static extraction time, CO2 density, and temperature were first investigated. These preliminary extractions revealed that a static period which afforded an opportunity for the polymer to swell combined with a high CO2 density and temperature above the polymer glass transition yielded quantitative recoveries of the additives. Triplicate extractions of the various polystyrene formulations matched additive recoveries obtained by the traditional dissolution/precipitation method but the former method was faster and used less organic solvent.