Dynamic mechanical properties of methacrylic-acid-grafted polyethylene films

A dynamical mechanical relaxation study has been made of low density polyethylene films to which methacrylic acid has been grafted by γ irradiation. The grafted films retain the original degree of crystallinity and show only slight changes in melting points and melt viscosities. This indicates that the grafted methacrylic acid side chains are long, few in number, and completely phase separated from the polyethylene matrix. Three dispersion regions are observed in plots of the loss modulus, E″ vs. temperature at constant frequency and these are labeled γ, β, α′, in order of increasing temperature. The α′ peak, above 215°C was assigned to microbrownian segmental motions accompanying the Tg of polymethacrylic acid. The β peak, at −20°C, was assigned to motions accompanying the Tg of branched polyethylene, and the γ peak, at −120°C, was assigned to local motions of a few CH2 sequences in polyethylene.