Research On Tribological Property Of Mesoporous Silica Reinforced Polyimide-matrix Composites

The increasing application of polymer-based self-lubricating materials in kinematic pair such as self-lubricating spherical plain bearing proposes urgent imperative demand for the development of new polymer-based self-lubricating materials,which is supported by the fundamental research of polymer tribology.Polyimide(PI)based self-lubricating composites have been widely applied in fields of aviation,aerospace,machinery etc.However,anti-friction and anti-wear properties of pristine PI are still poor when it is used as friction material,and tribological mechanism regarding PI materials also remains to be further studied.The particular nano porous structure of mesoporous silica has the unique ability of penetrability to polymer chains,which is able to form micro/nano scale reinforcing structure within polymer matrix and thus produces significant impact on properties of polymers.Such structure is expected to produce promotion effect on tribological property of PI.In this thesis,one kind of mesoporous silica(MPS)was used as modification material to fabricate MPS midified PI composites.The tribological property of MPS midified PI composites was studied.Focusing on friction interface,the tribological mechanism of MPS midified PI composites was investigated from the points of view of interfacial tribochemistry and formation mechanism of transfer film.Based on above study,the fabrication and property evaluation on new PI based self-lubricating material were conducted.In this thesis,firstly,nano-size MPS and thermoplastic PI were synthesized respectively to fabricate PI/MPS nanocomposites.Mechanical,thermal and tribological properties of PI/MPS nanocomposites were systematically studied and the MPS was found to be able to effectively improve the friction and wear property of PI.Secondly,the tribological mechanism of PI/MPS nanocomposites was investigated from the points of view of interfacial tribochemistry and formation mechanism of transfer film.Complex tribochemical reaction including decomposition of PI was revealed within the friction interface during the sliding between PI/MPS nanocomposites and bearing steel,which dominated the formation mechanism of the transfer film and produced significant impact on the friction and wear property of the composites.Furthermore,the tribological property of PI/MPS nanocomposites was continuously optimized by means of single or multi modification using solid lubricants and fibers.PI/MPS based composites with preferable tribological property and mechanical strength were obtained.Finally,the tribological property of above-mentioned PI/MPS based composites under extensive relative sliding speed and applied load(PV value)was systematically investigated and the P-v maps of the friction pairs consisting of the composites and bearing steel at atmospheric environment were obtained,which provided research basis and data support for the actual application of PI/MPS based composites.In this dissertation,with the study of tribological effect of MPS on PI as breakthrough point,the promotion effect of MPS on the tribological property of PI was verified.PI/MPS based composites possessing both good tribological property and mechanical property were successfully fabricated.Tribological mechanism of PI composites was revealed from points of veiw of tribochemistry and transfer film formation,which produced theoretical significance and practical value on the development of advanced polymer-based self-lubricating materials.