Changes of Characteristic Endothermic Peak of Ionomers Induced by Various Heat Treatments

This study investigates the characteristic endothermic peaks of ionomers, Ti, appears at lower temperature than the melting point. We evaluate the thermal properties of ionomers under various heat treatment conditions with DSC. The Ti peak temperature and endothermic peaks area increase with longer heat treatment time. For more detailed analysis, we evaluate the nanoscale structure with small-angle and wide-angle X-ray scattering measurements. The correlation length between polyethylene crystals increases with increasing temperature above Ti. The results showed that the Ti peaks are very sensitive to heat treatment conditions, especially to the nanoscale structure. Furthermore, the radius of core of ion-aggregates and that of the immobile polymer layer was very sensitive of temperature. From these results, precise analysis also showed that the change in Ti peaks is due to the important role of molecular motion in the amorphous regions between crystals. We also showed that the appearance of Ti peaks depends on the interaction of ions with the carboxylic acid ion of polymers.