Direct preparation of porous polyethylene filters by radiation polymerization of ethylene

Abstract

AbstractIn order to prepare porous, macroscopically homogeneous filters without a separate packing process, ethylene was polymerized by radiation in glass tubes. The bulk density of the polyethylene is approximately proportional to ρ(ƒM)2I0.9t2, where ρM is average ethylene density, ƒM is average ethylene fugacity, I is radiation dose rate, and t is reaction time. The effect of the bulk density on “treatment capacity” was investigated by experiments where air samples containing 0.1 wt‐% iodine vapor were filtered. Treatment capacity is difined as that amount of air per gram of polyethylene which passes through a filter until the polyethylene reaches the break point. The treatment capacity is approximately constant at 9 × 102 cm3/g over the bulk density range from 0.03 to 0.07 g/cm3, and it is lower at the outside of this range. The pressure drop due to the polyethylene filters varies with the 2.7th power of the bulk density when the bulk density is more than 0.03 g/cm3; below 0.03 g/cm3 this exponent increases with decreasing bulk density. Because of both the necessity of high Treatment capacity and that of low pressure drop, the optimum bulk density of polyethylene in the filter is about 0.03 g/cm3.