PVC 2011: The Eleventh International PVC Conference: supercritical fluid-assisted processing of UPVC

A modified extrusion system was used to demonstrate the viscosity-reducing effect of supercritical carbon dioxide in unplasticised PVC, together with a capability to produce foam-free extrudate. This was accompanied by significant reductions in extruder motor power and an increase in material output. After subsequent diffusion of the gas, the properties of materials processed with and without carbon dioxide remained the same. It was also found that exposure to supercritical carbon dioxide had a significant effect on the rate and extent of PVC gelation using static tests in a pressure vessel (without the application of shear) during compounding in a Haake batch mixer and in a co-rotating twin-screw extruder. 10 refs.