EFFECT OF HYDROGEN-BONDING AND IONIC AGGREGATION ON MELT RHEOLOGY OF AN ETHYLENE-METHACRYLIC ACID COPOLYMER AND ITS SODIUM SALT

A study has been made of the dynamic and steady shear melt rheology of an ethylene-methacrylic acid copolymer, its methyl ester, and 70% neutralized sodium salt. Correspondence was found between steady shear viscosity and the complex dynamic viscosity for the ester and acid materials. Over the temperature and frequency range studied the time-temperature superposition principle was applicable to G prime data for each of the derivatives and a supermaster curve could be constructed from the three individual master curves. Time-temperature superposition was found not applicable to G double prime data for the sodium salt. Differences in rheological response between the ester and acid copolymers are explained by differences in T//g. It is suggested that differences in temperature shifts DELTA T required to produce G prime superposition between the three derivatives reflect differences in DELTA H for interchain interactions. A mechanism for flow of clustered ionomers is suggested consisting of an initiation and a propagation step.