中文摘要：

研究了0％～20％（质量分数）邻苯二甲酸二辛酯（DOP）与聚甲基丙烯酸甲酯（PMMA）混合后的相溶性。用差热分析（DSC）和动态机械分析（DMA）法表征了其玻璃化温度（Tg）和弛豫行为。Tg和α弛豫温度随DOP含量的增加而减小，表明DOP的添加改善了PMMA的塑性。在β弛豫区，损耗模量E＇＇的振幅几乎不随DOP含量的增加而改变。DMA测试也表明，低温处存在明显的局部运动。用单轴力学压缩测试研究其塑性行为，通过应力-应变曲线分析了屈服强度（σy）、塑性流动应力（σpf）及应变软化（SSA）与温度和DOP含量的关系。不同DOP含量时的瓦-丁关系曲线表明α运动在整个温度范围内对σpf起作用；σy在低温处由β运动起作用，在靠近Tg时α运动起作用。除低温外，所有的DOP／PMMA体系均呈现出很小的SSA值，这与强的β弛豫运动有关。

英文摘要：

Miscible mixtures of poly（methyl methacrylate） （PMMA） and di-octylphthalate （DOP） are investigated over the range 0 %- 20wt% of DOP. The glass transition temperature（Tg） and relaxational behavior are charac- terized by differential scanning calorimetry （DSC） and dynamic mechanical analysis （DMA）. Increase in DOP content improves the plasticization of PMMA, as revealed by the decrease of both Tg and α relaxation temperature. In the β relaxation region, the amplitude of E＂ loss peak is almost independent of the DOP content, showing the absence of any antiplasticization effect. This result is in good agreement with the intramolecular character of the PMMA β relaxation motions. DMA spectra also reveals, at low temperature, the occurrence of highly localized motions ascribed to the PMMA 7 relaxation. The plastic behavior of DOP/PMMA is deduced from compression tests. Use of the reduced temperature Tg - T for inspecting the plots at variable DOP content shows that σpf is controlled by the α motions all over the temperature range, whereas ay is governed by the β motions at low temperature and by the α motions while approaching Tg. Except at low temperature, all the DOP/PMMA samples exhibit a quite low SSA, in connection with the presence of a strong β relaxation.