Studies on Development of Tough Polymeric Materials at Cryogenic Temperatures

1.制备了PET/PEN=100/0、95/5、90/10、85/15、70/30、50/50、30/70、10/90、0/100的PET（聚对苯二甲酸乙二醇酯）和PEN（聚乙烯-2,6-萘二甲酸乙二醇酯）共聚酯。在83 K和296 K下测试了单轴拉伸膜的力学性能。PET/PEN=90/10共聚物薄膜具有特别优异的低温性能。结果表明，PET/PEN=90/10薄膜单轴拉伸5次，在应力水平为400 MPa，温度为83 K时，拉伸率可达40%以上。对比5次单轴拉伸PET/PEN=90/10薄膜在83 K下拉伸试验前后样品的DSC（差示扫描量热计）曲线。在83 K拉伸试验后，冷结晶峰位置发生位移，曲线与基线之间的峰面积减小，表明在83 K拉伸试验中允许发生结晶。测量了从18k到玻璃化转变温度范围内的介电损耗切线。在100 K以下，PET及其共聚物除了在230 K左右出现明显的弛豫最大值外，还观察到损耗水平的增加与形貌有关。在此基础上，讨论了聚合物的结构与低温性能之间的关系。测量了几种聚酰亚胺薄膜(Upilex-S - r （Ube Industries）、Kapton （duPont）和Regulus （Mitsui Toatsu Chemicals）的机械和介电性能。所有样品在低温下均具有优异的力学性能。这在一定程度上是因为，即使它们的片段运动在低温下被冻结，这些聚合物也会发生变形，因此通过改变主链键角仍然可以保持柔性。因此，这种聚合物可以包括其主链由氧（醚键）或各种杂环键组成的聚合物。

1.Copolyesters of PET (polyethylene terephthalate) and PEN (polyethylene-2,6-naphthalene dicarboxylate) with composition of PET/PEN=100/0,95/5,90/10,85/15,70/30,50/50,30/70,10/90,0/100 were prepared. The mechanical propertiesof uniaxial stretching films were examined at 83 K and 296 K.PET/PEN=90/10 copolymer film possessed especially excellent cryogenic properties. It was found to withstand elongations in excess of 40% at stress levels about 400 MPa at 83 K for 5 times uniaxial stretching PET/PEN=90/10 film.DSC (Differential Scanning Calorimeter) curves of samples before and after tensile test at 83 K were compared for 5 times uniaxial stretching PET/PEN=90/10 film. After tensile test at 83 K,the peak position of cold-crystallization shifted and the peak area between the curve and a baseline decreased, indicating that crystallization is allowed to take place during tensile test at 83 K.Dielectric loss tangent was measured in the temperature range from 18 K to the glass transition temperature. The increase of loss level below 100 K in addition to the pronounced relaxation maximum at around 230 K of PET and its Copolymers was observed with dependence on the morphology. On the basis of the results obtained, relationship between the structure of polymers and their cryogenic properties will be discussed.2.The mechanical and dielectric properties of several polyimide films (Upilex-S and-R (Ube Industries), Kapton (duPont), and Regulus (Mitsui Toatsu Chemicals) were measured. All samples had prominent mechanical properties at cryogenic temperatures. This is partly because, even when their segmental motions are frozen out at cryogenic temperatures, these polymers could undergo deformation, and hence could still flexible by changing the main chain bond angles. Such polymers may, therefore, include those whose main chains are composed of oxygen (ether linkage) or various heterocyclic linkages.