EFFECT OF IONIC INTERACTION ON LINEAR AND NONLINEAR VISCOELASTIC PROPERTIES OF ETHYLENE BASED IONOMER MELTS

The effect of ionic interaction on linear and nonlinear viscoelastic p roperties was investigated using poly(ethylene-co-methacrylic acid) (E /MAA) and its ionomers which were partially neutralized by zinc or sod ium. Dynamic shear viscosity and step-shear stress relaxation studies were performed. Stress relaxation moduli G(t, gamma) of the E/MAA and its sodium or zinc ionomers were factorized into linear relaxation mod uli G degrees(t) and damping functions h(gamma). The relaxation modulu s at the smallest strain in each ionomer agreed with the linear relaxa tion modulus calculated from storage modulus G' and loss modulus G ''. In the linear region, the ionic interaction shifted the relaxation ti me longer with keeping the same relaxation time distribution as E/MAA. In the nonlinear region, the ionic interaction had no influence on h( gamma) when the ion content was low. At higher ion content, however, t he ion bonding enhanced the strain softening of h(gamma).