Dynamic Shrinkage Behavior of Polyester Fiber under High Pressure Carbon Dioxide

Dynamic shrinkage behavior of poly(ethylene terephthalate) (PET) fiber was measured by heating in high pressure CO 2 at a constant heating rate. In the dynamic shrinkage behavior, the shrinkage temperature ( T s ) of PET fiber in high-pressure CO 2 was obtained from the extrapolation of equilibrium shrinkage region that the sample reached the equilibrium shrinkage with respect to the temperature during the measurement. The T s of PET fiber was lower in high-pressure CO 2 compared to in air. Its amount increased linearly with increasing CO 2 density, and the decrease of 40 ºC was observed in CO 2 with the density of 0.15 g/cm 3 . The amount of CO 2 sorption in PET fiber was increased with increasing the CO 2 density in the measurement atmosphere, which resulted in the further enhancement of the molecular chains mobility. The slope of the equilibrium shrinkage region with respect to the measurement temperature was smaller than the one in air. It decreased with increasing CO 2 density to 0.08 g/cm 3 but remained constant at the higher density.