Studies on Development of Tough Polymeric Materials at Cryogenic Temperatures

1.制备了组成为PET/PEN=100/0，95/5，90/10，85/15，70/30，50/50，30/70，10/90，0/100的PET/PEN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共聚物膜具有特别优异的低温性能。结果表明，PET/PEN= 90/10薄膜经5次单向拉伸后，在83 K下拉伸应力约为400 MPa时，拉伸伸长率超过40%，并比较了PET/PEN= 90/10薄膜经5次单向拉伸前后的DSC曲线。在83 K的拉伸试验后，冷结晶的峰位置移动，曲线和基线之间的峰面积减小，表明在83 K的拉伸试验期间允许发生结晶。在18 K至玻璃化转变温度的温度范围内测量介电损耗角正切。除了在230 K附近的PET及其共聚物的显著松弛最大值之外，还观察到100 K以下的损失水平的增加与形态的依赖性。在此基础上，讨论了聚合物的结构与低温性能之间的关系。2.测试了几种聚酰亚胺薄膜（Upilex-S和-R（宇部工业）、Kapton（杜邦）和Regulus（三井东压化学））的力学和介电性能。所有样品在低温下具有突出的机械性能。这部分是因为，即使它们的链段运动在低温下冻结，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弯曲。因此，这样的聚合物可以包括主链由氧（醚键）或各种杂环键组成的那些。

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.