The effect of styrene grafting on the diffusion and solubility of organic liquids in polyethylene

The effect of grafting styrene onto low-density polyethylene on the diffusion and solubility of benzene and n-hexane in the graft copolymer has been investigated. The diffusion coefficient at zero concentration D_{c = 0} for both benzene and n-hexane decreased with the amount of styrene grafting in the polyethylene–styrene graft copolymer membrane. The free volume parameters of the polyethylene–styrene graft copolymer were calculated using benzene and n-hexane as the diffusing species. Results show that there is a large decrease in free volume as grafting proceeds and the effect is more pronounced at low levels of grafting. Solubility was found to be a function of the per cent grafting, there being a 50%–90% increase in benzene solubility in a 26% graft compared to polyethylene. The increase in solubility for n-hexane was considerably lower. The effect of crystallinity on the free volume parameters has also been calculated.