Ion‐conducting grafted polypropylene film, 2. Volume grafting of polypropylene and gradient composition of poly(propylene‐g‐acrylic acid)

Grafting of acrylic acid onto a pre‐activated polypropylene film was investigated, varying the concentrations of monomer and Fe2+ ‐ions, the polymerization time and temperature. Experiments were planned according to a scheme of a latin square, and statistical analyses were performed for the optimization of the grafting variables. The concentration of ferrous ions was found to be the most significant variable for the graft level. At low concentration, ferrous ions act as activator of grafting but no grafting takes place at relatively high concentrations. The distribution of grafted poly(acrylic acid) within a PP film was examined by microphotometry of the coloured slides of the film. The grafted layer of PP reaches the center only at about 30% of grafted poly(acrylic acid) and up to 70% the distribution of grafted poly(acrylic acid) is still non‐uniform with a decreasing amount of the polyacid from the surface to the center. The film samples containing 30% of grafted poly(acrylic acid) already show conductivity in alkaline media and are interesting ion conducting materials.