| Polytetrafluoroethylene (PTFE) is more and more important in our lives and wide variety industries are using PTFE resins directly or indirectly. Currently, there are three types of PTFE resin, including granular PTFE, fine powder PTFE and PTFE dispersions. Because PTFE has a lot of excellent properties, such as high chemical resistant, wide temperature range, good solvent resistance and insulating properties, it can be used in various environments. Therefore, PTFE has been widely used in high-technical industries, such as aero-craft and aero-space industry, general industry and medical industry, etc.PTFE fine power can be made of inner tube of PTFE hose assembly. As the high-performance flexible connection pipe, PTFE hose assembly has the characteristic of high temperature-resistant, high pressure-resistant, corrosion-resistant, excellent electrical properties and many other advantages, and PTFE hose assembly has been widely used in national defense. The development trend of PTFE hose assembly has the following three aspects: the application fields will expand from military to civil aviation; the direction of standardization products and the direction of diversification.Stress cracking is the main reason that PTFE high pressure hose assembly failed. Some applications require flexibility to bend and curl the hose, according to the working environment of PTFE hose assembly, it needs an excellent flexible performance. Lower permeability and higher flex life require a polymer with minimal void content after sintering. It can be accomplished by lowering the molecular weight to reduce melt viscosity, and thus improving coalescence. Lowering the molecular weight normally results in higher crystallinity, therefore, reduced flex life.To overcome this dilemma, the modified PTFE (Resin B) by copolymerizing a small amount of another perfluorinated monomer is used to prepare the hose. A small amount of the comonomers are sufficient to disturb the crystallinity of PTFE, which leads to a more amorphous phase. The use of Resin B can increase the flex life and decrease the gas permeability of the PTFE hose obviously.In order to analyze the performance difference between PTFE pressure hose assembly made of different PTFE fine powder, Resin A and B are compared via scanning electron microscope (SEM), differential scanning calorimeter (DSC), X-ray Diffraction (XRD), impulse test, assembly flexibility test, pressure test, high-temperature aging test, stretch void index test and orientation index. It is found that Resin B has less crystallinity and therefore, the hoses made from Resin B have enhanced flex life, anti-stress-cracking and isotropic performance. The hose assembly on aircraft can reduce the possibility of stress cracking, which will ensure the aircraft safety. |
