Study On Preparation And Tribological Properties Of Polyimide And Composites

The energy loss and material loss caused by friction and wear are difficult problems in the world.It is urgent to develop new wear-resistant materials.Polyimide(PI)is an aromatic heterocyclic polymer with amide bond in the main chain.Because of its high strength,light weight and good flexibility of molecular chain,PI is widely used as wear-resistant parts such as bearings and gears.However,the tribological properties of pure polyimide are not good enough.It is necessary to modify its tribology by adding tribofilm and changing the molecular structure.Therefore,graphene oxide/polyimide(GO/PI),carbon nanotube/polyimide(CNT/PI)and fluorinated and sulfur-containing polyimide materials were prepared in this paper.The effects of go and CNT nano fillers on the tribological properties of PI at room temperature and the effects of fluorine and sulfur atoms on the tribological properties of PI under wide temperature range were studied.The main studies include:1.Graphene oxide(GO)was introduced into polyimide(PI)prepared by4.4?-diaminodiphenyl ether(ODA)and 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride(BPDA)to prepare graphene oxide/polyimide composites.The tribological properties of polyimide and graphene oxide/polyimide composites were investigated by a multifunctional friction and wear tester.The results showed that the modulus and hardness of polyimide were significantly improved by the addition of graphene oxide.When the mass fraction of GO was 0.1%and 0.3%,the tribological properties of the composites were better It is found that the transfer film formed on the metal dual surface plays an important role in the tribological properties of polyimide composites.2.Carbon nanotubes(CNT)was introduced into polyimide(PI)prepared by4.4?-diaminodiphenyl ether(ODA)and 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride(BPDA)to prepare graphene oxide/polyimide composites.The addition of CNT enhanced the strength,modulus and hardness of PI matrix.In addition,the friction coefficient(0.05)and specific wear rate(1.0×10^-6mm³/N·m)of PI composite with 1.0 wt.%CNT were significantly lower than those of pure PI,which were 90.7%and 82.0%lower than those of pure PI.It is found that CNTs and tribochemical products continuously enter into the friction film,which enhances the lubricity and load-carrying capacity of the friction film.3.The tribological properties of common polyimide(PI),fluorinated polyimide(FPI)and sulfur-containing polyimide(SPI)in a wide temperature range were studied by high and low temperature friction and wear tester.It was found that the incorporation of fluorine and sulfur atoms into polyimide had a significant effect on their mechanical and tribological properties.Generally,the wear rates of FPI and SPI are much higher than PI,and FPI displays the worst friction coefficient.To deeper reveal the fundamental reasons,the FTIR,XPS,EDS,SEM characterizations were carried out combined with molecular dynamic simulation.The calculation results from the Molecular Dynamics model between PI and Fe showed that the interaction potential energy of SPI and FPI was larger than that of PI due to the polarization of F and S.Judged from the structures of transfer film,SPI and FPI was easily adhered on the surface of counterpart,even chemical reaction.The XPS analysis further confirmed the possibility of tribo-chemical reactions between SPI/FPI and Fe.This study will provide the theoretical guidance for other polymer molecular design and its tribological research.