Design and Synthesis of Advanced Composites for Cryogenic Uses

本研究的目的是为设计和合成适用于低温环境的先进复合材料积累基础信息。从第一年的实验结果来看，能够改变主链键角的聚合物似乎具有优异的低温性能。这部分是因为，即使当它们的链段运动在低温下冻结时，这些聚合物也可以发生变形，因此仍然可以通过改变主链键角而具有柔性。在第二年的实验中，研究了聚合物的结晶度与低温性能之间的关系。聚苯硫醚在77 K时的强度和断裂伸长率随结晶度的增加而增加，而聚萘二甲酸乙二醇酯在77 K时的力学性能随结晶度的增加而降低。这些结果表明，聚合物的形态极大地影响其低温性能。聚合物复合材料的几种性能取决于大量因素，例如树脂含量、基质系统的相对柔性、固化温度和压力、固化和后固化周期以及纤维的表面处理。这些研究结果为开发新型低温复合材料提供了有益的参考。

The purpose of this study is to accumulate the fundamental information for design and synthesis of advanced composites usable in cryogenic environments, From the results obtained in experiments of the first year, it is suggested that the polymers which are able to change the bond angles of the main chain seem to excel in cryogenic properties. This is partly because, even when their segmental motions are frozen out at cryogenic temperatures, these polymers could undergo deformation, and hence could still be flexible by changing the mainchain bond angles. In the experiments of the second year, the relationship between the crystallinity of polymers and the cryogenic properties was studied. The strength and the elongation at break point of polyphenylene sulfide at 77 K increase with an increase in the degree of crystallinity, In the case of polyethylene naphthalate, however, both mechanical properties at 77 K decrease with increasing the degree of crystallinity. These results indicate that the morphology of polymers greatly affects their cryogenic properties. Several properties of polymer composites are dependent on large number of factors such as resin content, relative flexibility of the matrix system, curing temperature and pressure, cure and post-cure cycle, as well as surface treatment of fibers. These findings offer us the useful information for developing the new type of advanced composites for cryogenic applications.