Oxygen Permeability of Polypropylene Containing Polyisobutene with Magnesium Acetate

The oxygen permeabilities of polypropylene films are reduced by adding a minor percentage of a polyisobutene ionomer. The polyisobutene ionomers were prepared by in situ salt exchange of magnesium acetate with maleated polyisobutenes of commercially available low relative molecular mass. The more polar magnesiurn salts aided phase separaion during crystallization from the molten polypropylene mixtusre. Scanning electron microscope photographs revealed that the polyisobotene ionomer is largely concentratd in the amorphous regions between the polypropylene spherulites, where the ionomer tends to concentrate during crystallization. The influence of the polyisobutene ionomer on the oxygen permeability of polypropylene was found to be slightly dependent upon the relative molecular mass of the polyisobutene precursor. Under optimum conditions, the oxygen permeability of polypropylene is reduced by 20% with only 1% additive.