The Investigation On Synthesizing And Tribological Properties Of Fluorinated Polyimides

Tribological studies have now deepened into the molecular level. With the use of advanced surface mechanical device, it have been found, in the micro-tribology studies of polymer, that the molecular chains of the structure and monomer arrangement in polymers significantly affected the physical and chemical properties, thereby affecting the mechanical and frictional performances. During physics researches in the 21st century, condensed matter physics of material is recognized as the most likely area of the breakthrough. Polymer material, as the soft material, has become an important material widely concerned. Therefore, there is an urgent need to understand relationships between the chemical structure and condensed matter structure of polymer materials and tribological properties.Fluorinated polyimide (FPI) were synthesized. Through the study of the structure to FPI basic function and tribological properties, from molecular design mechanism, and explore new ways for high polymer materials developed in micro-tribological area. FPI of various structures were synthesized, choosing different kinds of monomers, characterized and tested with mechanical and tribological performances. Systematic studies about influences of fluorine polyimide structure on tribological properties of polyimide were implemented, and summed up the relationship between structure and tribological properties. Furthermore, it was proposed the friction and wear mechanisms of different structure PIs.The conclusions of this dissertation were drawn as follows:1. FPI with different kinds of structures and content of fluorinated monomers have been synthesized succesfully. Test results show that the introduction of fluoride unit can significantly change FPI tribological performances. With the increase of the content of fluoride monomer, heat-resistance, friction coefficient and abrasion resistance of the materials, obviously occurs improvement. Friction coefficients of non-fluorinated and fluorinated polyimides based on ODA/ODPA were 0.33 and 0.21 respectively, the wear rate of fluorinated polyimide was only half of fluorinated polyimide.2. FPIs of flexible molecular chain structures have lower surface energy, low friction coefficient, but the strength of material is not high, while FPIs of rigid structure exhibited higher surface energy, strength, good abrasion resistance, but higher friction coefficient. With molecular chain rigidity of polyimides synthesized from ODPA, BPDA and PMDA increased gradually, strength and wear rate reduced, and friction coefficient is gradually increasing.3. With the increase of FPI molecular, tensile strength and heat-resistant improvements were closely related to increase molecular interactions.Introduction of crosslinking FPI failed to significant in action, that may related to BMI structure incur lower heat-resistance and offset the some positive effect.4. The results from mechanism reasoning indicate the that:the lower surface energy of fluorine material was the essential reason of the friction coefficient reduction. Higher electronic polarizability of fluorine element brings high polymer material strength in intercropping force and heat-resistant improvement, which could be the cause of improved abrasion resistance.