The use of temperature variation in supercritical fluid extraction of polymers for the selective extraction of low molecular weight components from poly (ethylene terephthalate)

Abstract

The extraction of poly (ethylene terephthalate), PET, using a Soxhlet extractor is a widely used procedure for the determination of migratory compounds. The use of supercritical fluid extraction, SFE, makes it possible to determine the oligomer content in a much shorter analysis time. A systematic study of the influence of temperature, pressure (density) and mobile phase composition shows that it is not only possible to increase the speed of extraction but also to conduct a multi-step extraction of PET fibers. The method allows the automation of the whole analysis using a selective two step supercritical fluid extraction of the oligomers, firstly from the fiber cover and then from the core of the fiber. The systematic study of the influence of temperature has led to a model for dynamic extraction with supercritical fluids which considers the temperature-dependent physical changes in polymers. A simple rule for estimating the optimum temperature for the SF extraction of polymers is suggested.