Studies on Development of Tough Polymeric Materials at Cryogenic Temperatures

通过对聚甲基丙烯酸甲酯（PMMA）、聚甲基丙烯酸乙酯（PEMA）以及在部分侧链上标记有NLO染料（对硝基苯胺和N-甲基-4-硝基苯胺）的PMMA的热性能和介电性能的测量，研究了物理老化对PMMA的影响。随着物理老化时间的延长，所有样品的吸热峰面积均增大，峰位发生了高温位移，介电损耗角正切随温度的变化规律可以清晰地观察到从物理老化的紧密堆积状态到平衡状态的变化。介电常数的真实的和虚部都发生了变化，不存在频率依赖性。这一结果表明，对物理老化引起的结构变化有新的认识是必要的.合成了PET（聚对苯二甲酸乙二醇酯）/PEN（聚2，6-萘二甲酸乙二醇酯）共聚酯，PET/PEN= 90/10。通过在熔点以上压制并在冰水中淬火获得非晶膜（样品1）。由样品1制备单轴自由宽度5倍拉伸膜（样品3）。样品1和样品3在347 K下退火24小时（分别为样品3和样品4）。对于样品3观察到介电伽马弛豫（在10 kHz下约50 K），并且对于样品4明显降低。由于这种弛豫被指定为缺陷区域的运动，物理老化的效果是缩小缺陷区域或抑制缺陷的运动。在0.1 Hz时，在100 ~ 300 K的温度范围内，样品2的弹性模量高于样品1;在77 K时，样品2的杨氏模量高于样品1，而样品4的杨氏模量、断裂强度和伸长率低于样品3。

Effects of physical aging have been investigated by thermal and dielectric measurements for Poly(methyl methacrylate)(PMMA), poly(ethyl methacrylate)(PEMA), and PMMA labeled with NLO dye(p-nitroaniline and N-methyl-4-nitroaniline) in part of the side chain. The increase of the endothermic peak area and the high temperature shift of the peak position were observed as the physical aging time increased for all samples measured in this study.We were able to observe clearly the change from closely packed state by physical aging to the equilibrium state in the temperature dependence of dielectric loss tangent. The change appeared in both the real and imaginary parts of the dielectric constant and the frequency dependence did not exist. This results indicate that new idea about the structural change due to physical aging is necessary.2. Copolyesters of PET(polyethylene terephthalate) and PEN(polyethylene-2,6-naphthalene dicarboxylate) with composition of PET/PEN= 90/10 was prepared. Amorphous film was obtained by pressing above the melting point and quenching in ice water(sample 1). Uniaxial free width 5 times stretching film was prepared from sample 1 (sample 3). Sample 1 and sample 3 were annealed at 347K for 24hr(sample3 and sample 4, respectively). Dielectric gamma relaxation(-50K at 1 0kHz) observed for sample 3 and decreased clearly for sample 4. As this relaxation was assigned as the motion of defect region, effects of physical aging are diminution of defect region or suppression of defect's motion. For temperature dependence of the tensile modulus at 0.1 Hz, the modulus of sample 2 was high value than that of sample 1 in the temperature range from 100K to 300K.In tensile test at 77K, Young's modulus of sample 2 showed high value than that of sample 1.But, Young's modulus, tensile strength at break and ultimate elongation of sample 4 were low value than these of sample 3.