Study On Surface Modification And Tribological Properties Of Polymer

In nature,different micro-nano structures on the surface of plant leaves can lead to different biological properties of plants.From the point of view of bionics,smooth films and bionic texture films of three different materials,polyvinyl alcohol(PVA),sulfonated polyether ether ketone(SPEEK),and sulfonated polyether ether ketone/polytetrafluorowax(SPEEK/PFW),were prepared by salivation-transfer process.The molecular structure,thermal properties and mechanical properties of the films were investigated.Tribological properties of three smooth films and their corresponding bionic textured films under dry friction were systematically studied.For different kinds of thin films,the effects of load and rotational speed on the tribological properties of thin films were also studied.The composition and morphology of wear marks were comprehensively investigated by using X-ray photoelectron spectroscopy(XPS),field emission scanning electron microscopy(SEM),optical microscopy(OM)and three-dimensional profilometer.The wear reduction mechanism of bionic textured films was obtained by analyzing the test results.The work completed in this study is described below.(1)Through the analysis of the plant leaves’ surface and biomimetic texture film by optical microscopy(OM),the surface of biomimetic texture film successfully copied the micro-structure of plant leaves.So,this methodhas successfullycompleted the modification of the surface of polymer film.At the same time,the effects of bionic texturing on the molecular structure and thermal properties of polymer films were studied.FTIR and TGA analysis showed that bionic texturing had no effect on the molecular structure and thermal properties of polymer films.This modification method only changes the surface structure of the polymer film,does not destroy the original molecular structure and properties of the polymer,and the mechanical properties of biomimetic textured films are better than smooth films.(2)When the load is 5 N and the speed is 200 r/min,the friction coefficients of M-PVA and C-PVA biomimetic texture films are 0.09 and 007,respectively.Compared with smooth films,the friction coefficients of M-PVA and C-PVA biomimetic texture films decrease by 0.06 and 0.08,respectively.With the increase of load,the friction coefficients of the three kinds of films show an upward trend,but the two kinds of bionic textured films change less with load.When the load increases by 2 N,the friction coefficients only increase by 0.02,while the smooth films increase by 0.05.With the increase of rotational speed,the friction coefficient decreases first and then increases,which is in accordance with the theory of polymer friction.(3)Under friction conditions,the friction coefficients of F-SPEEK and C-SPEEK biomimetic textured films are lower than those of smooth SPEEK films at load of 5 N and rotational speed of 200 r/min,which decrease by 0.13 and 0.15,respectively.This is because on the one hand,bionic texture can reduce the contact area between friction pairs,on the other hand,it can accommodate debris in the friction process,which prevents the debris from scratching the friction surface further.At the same time,under the action of friction heat and friction force,the bionic texture morphology becomes fish scale,reduces the friction in friction,and reduces the friction coefficient and wear rate.Under sea water lubrication,the two textured films also exhibit excellent tribological properties.(4)After adding PFW,the friction coefficient of the film decreases as a whole.The friction coefficients of the A-SPEEK/PFW andC-SPEEK/PFW biomimetic textured films are kept at about 0.1 in the range of 3-11 N load,which shows good friction stability.With the increase of rotational speed,the friction coefficients show an upward trend,and the rules of the two biomimetic textured films are different,which is due to the different surface structures of the biomimetic textured films.The research in this thesis shows that the micro-structure of plant leaf surface can be successfully copied on the surface of polymer film by salivation transfer printing process.Under dry sliding conditions,the bionic texture exhibits excellent tribological properties,and the maximum friction coefficient can be reduced by 0.15.This provides a new idea for the modification of polymer,and provides a new method for the preparation of bionic texture.Further optimization of bionic texture morphology is of great significance topromote the development of bionic tribology.