Impregnation of polyethylene (PE) with styrene using supercritical CO2 as the swelling agent and preparation of PE/polystyrene composites

Impregnation of low-density palyethylene (LDPE) with styrene using supercri tical (SC) CO2 as the swelling agent was studied at 35 degreesC in a pressu re range from 90 to 160 bar. The concentration of styrene in the fluid phas e ranged from 0 to 1.668 mol/L. The soaking time varied from 4 to 36 h. In the presence of azobis(isobutyronitrile), the initiator, styrene polymerize d to some extent in the soaking process, which results in an increase in th e mass uptake. LDPE/polystyrene (PS) composites were prepared by the polyme rization of styrene further in SC CO2-swollen LDPE substrates at higher tem perature. Using this method, the composition of the composites can be contr olled by the soaking time, pressure, and styrene concentration in the fluid phase. Some of the PS molecules in LDPE/PS blends entangle with the polyet hylene molecules, which causes significant improvement in the impact streng th, the tensile strength, and the elongation at the break.