Phase behavior of supercritical CO2/styrene/poly(vinyl chloride) system and synthesis of polystyrene/poly(vinyl chloride) composites

The phase behavior of the supercritical (SC) CO2/styrene/poly(vinyl chloride) (PVC) system was studied at 40 degrees C in the pressure range from 80 to 160 bar. The styrene concentration in the fluid phase ranged from 0 to 0.4 mol/L. The mass uptakes of styrene in PVC films before and after depressurization were obtained. A considerable amount of styrene in the films was carried out by CO2 in the venting process. When styrene contains 0.3 mol % initiator 2,2'-azobis(isobutyronitrile) (AIBN), the mass uptake is much higher than that in the absence of the initiator. The mass uptakes can be controlled by soaking time, pressure, and styrene concentration. PVC/polystyrene (PS) composites were prepared by the polymerization of styrene in PVC substrates. Scanning electron microscopy indicates that the original PVC gains are broken into the primary particles in the course of SC CO2 swelling at the low temperature of 40 degrees C, and the PVC primary particles force the PS particles to be well dispersed between them. The mechanical measurements show that the addition of PS not only can toughen brittle PVC but also can reinforce it in the PS content range from 0.074 to 0.24 g/g.