Design And Preparation Of Polyimide Composites And Tribological Properties Research

Polyimide（PI）,a class of polymeric Materials containing benzene rings,has been adopted in the field of tribology for its excellent mechanical properties,temperature resistance and self-lubricating properties.However,when it is used directly in wear-resistant coatings,problems such as high friction coefficient and insufficient wear resistance may be encountered.To meet the requirements of various complex and severe working conditions,the performance of polyimide can be improved by modification.In this paper,the compositions and structures of polyimide were modified to develop composites with different structures,including fabric/polyimide composites,polyurea/polyimide copolymer（PUA/PI）and polyurea/polyimide/titanium carbide copolymer（PUA/PI/Ti₃C₂）composites.For these materials,the tribological properties of CF-PI,AF-PI and PI were comparatively studied at 25～200℃,as well as the effects of PUA and Ti₃C₂ on the tribological properties of PI under high and low temperature conditions.Specific studies include:（1）Polyimide prepared from 4.4’-diaminodiphenyl ether（ODA）and 3.3’,4.4’-biphenyltetracarboxylic dianhydride（BPDA）was used to impregnate carbon fiber fabrics to obtain carbon fiber/polyimide composites（CF-PI）,and aramid fiber/polyimide composites（AF-PI）were obtained in the same way,and the tribological properties of CF-PI,AF-PI,and pure PI at 25～200℃were investigated comparatively by using high and low temperature/vacuum tribological wear testing machine.The findings show that AF-PI has better tribological properties at room temperature,while CF-PI has excellent wear resistance at 200℃.And the reduction of mechanical properties of CF-PI at 200℃,the interfacial interaction is weakened and a homogeneous polymer-based transfer film is formed.（2）Polyimide（PI）and polyurea（PUA）were cross-linked and copolymerized using 4.4’-diaminodiphenyl ether（ODA）as a cross-linking agent to obtain different component polyimide/polyurea copolymers.The mechanical properties and tribological performance of the copolymers under high and low temperature environments were investigated by adjusting the ratio of PI and PUA segments.The results showed that PUA and PI had good co-operative effect in the composites,which led to excellent mechanical properties of the composites.In addition,the composites have good tribological properties at the mass ratio of PUA to PI of1:6.（3）A series of polyimide/polyurethane-based copolymer composites were prepared by in situ introduction of different contents of titanium carbide（Ti₃C₂）into the copolymer PUA/6PI,and their frictional properties were tested under high and low temperature environments.The results showed that the addition of a small amount of Ti₃C₂ significantly reduced the frictional wear of the frictional substrate.SEM and XPS results showed that a continuous transfer film consisting of a high proportion of frictional chemical products and Ti O₂ was formed during the friction process,which significantly improved the lubrication performance at different temperatures.