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）和在部分侧链上用NLO染料（对硝基苯胺和n -甲基-4-硝基苯胺）标记的PMMA进行热学和介电测量，研究了物理老化的影响。随着物理老化时间的延长，本研究所测样品的吸热峰面积增大，峰位的高温位移增大。我们可以清楚地观察到介质损耗切线的温度依赖性从物理老化的紧密堆积状态到平衡状态的变化。介电常数的实部和虚部均出现变化，且不存在频率依赖性。这一结果表明，有必要对物理老化引起的结构变化提出新的认识。制备了PET/PEN= 90/10的聚对苯二甲酸乙二醇酯（PET）和聚2,6-萘二甲酸乙二醇酯（PEN）共聚酯。将其压在熔点以上，在冰水中淬火，得到非晶膜（样品1）。从样品1（样品3）制备单轴自由宽度为5倍的拉伸膜。样品1和样品3在347K下退火24h（分别为样品3和样品4）。样品3观察到介电伽马弛豫（-50K, 10khz），样品4明显下降。由于这种松弛被指定为缺陷区的运动，物理时效的影响是缺陷区的缩小或缺陷的运动受到抑制。对于0.1 Hz下拉伸模量的温度依赖性，在100K ~ 300K温度范围内，样品2的模量比样品1的模量高。在77K的拉伸试验中，试样2的杨氏模量比试样1高。试样4的杨氏模量、断裂抗拉强度和极限伸长率均低于试样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.