PS와 PMMA 아이오노머의 열적 유도 치유

Abstract

In this study, the thermally induced healing of PS and PMMA ionomers was investigated. To conduct the experiments, the surface of the ionomers was cut by using a tool, weighing 1 kg, equipped with a cutter knife and wheels. Then, the ionomers were placed in vacuum ovens of three different temperatures for varying periods of time. After that, the scars on the ionomer surfaces were photographed by using an optical microscope with magnification of x150. As the first part of the study, the effects of the degrees of neutralization (0, 30, 50, 70 and 100 %)and the ion contents (3.9, 6.5 and 10.0 mol%) of the PS ionomers on the ionomer's thermal-induced healing were investigated. In addition, the effect of temperatures (120, 130, 140 °C) for thermal treatments on the ionomer's healing was also studied. It was found that with increasing ion content and neutralization degree the thermal-induced healing of the ionomers decreased. Furthermore, only the ionomer samples thermally treated at 120 °C showed strong neutralization degree effects. On the other hand, the ionomer samples treated at 130 and 140 °C exhibited only minor effects. In addition, it was also observed that the storage modulus of the ionomers at the temperature of interest significantly affected the healing behavior of the ionomers. As the second part of the study, the effects of polarity of polymer backbones and types of cation of the ionomer healing behavior were investigated. To do the work, the PS (SMA) and PMMA (MMA) ionomers were prepared and the acid groups of the ionomers were neutralized with various cations; the cations of different radii (Na+ vs. Cs+), different charges (Na+ vs. Ba2+), and from alkali metal and transition metals (Ba2+ vs. Zn2+). It was observed that SMA and MMA ionomers showed different matrix Tgs and cluster Tgs and storage moduli because of their polarity difference. Thus, when the SMA and MMA ionomers thermally treated at the same temperature, the SMA ionomers, having relatively lower matrix Tgs and storage moduli in comparison with those of the comparable MMA ionomers, exhibited better healing behavior that the MMA ionomers. Finally, it was found that the healing of Zn-neutralized ionomers was more profound than those of the ionomers neutralized with the rest of the cations. Thus, it was proposed that the better healing of the Zn-ionomers was due to both under-neutralization and internal plasticization effects.