Preparation, Characterization And Research On Tribological Properties Of Polymer Nanocomposites Based On Zirconia And Molybdenum Disulfide

Inorganic/polymer nanocomposites have received some interests in a wide range of scientific and industrial fields.These materials have better electrical,thermal,chemical activity,optical properties and extend their range of industrial applications.Compare with metal materials, Inorganic/polymer nanocomposites used for self-lubrication materials have attracted more and more attention because they displaying different characteristics,such as friction reduction,self-lubrication, wear resistance,corrosion resistance,shock absorption,noise reduction and easy to fabrication. Nanometer inorganic particles hard to disperse in polymeric matrix uniformly because their high surface energys.Therefore,the effect of compound between inorganic and polymeric meterials depends on the preparation process to a great extent.In this paper,differect kinds of inorganic/polymer nanocomposites were prepared via various ways.The interaction between nanometer inorganic particles and polymer were discussed.The compounding principle,structures and performances of nanocomposites were researched.The tribological peoperties of inorganic/polymer using for lubrication additives and friction couples were also investigated.1.Preparation of ZrO₂/polymer hybrid nanoparticles with ionic bonding.The ionic initiator potassium persulfate(K₂S₂O₄) were used,based on the positive charged colloidal particles generated from hydrolysis of zirconium oxychloride(ZrOCl₂).The inorganic ZrO₂ core were combined with polymer by means of the positive and negative attraction.S₂O₄^2- were attracted onto the zirconium colloidal particles and then initiating the polymerization of styrene.The effect of pH on the hydrolysis and condensation of ZrOCl₂ were studied.The effect of pH of zirconium sol on the polymerization methods were researched.The core-shell hybrid nanoparticles in the range of 70～80nm were synthesized by means of emulsion polymerization and soap-free emulsion polymerization,respectively.These nanoparticles have controllable structure,even particle size and good thermal stability.This experiment provides a new idea to product the low-cost, structure-controllable and large-quantity core-shell hybrid nanoparticles.2.Preparation of ZrO₂/polymer hybrid nanoparticles with covalent bonding.The core-shell ZrO₂/PAAEM/PS nanoparticles were synthesized through the combination of a sol-gel method and an soap-free emulsion polymerization approach.By this method,the modified nanometer ZrO₂ cores were prepared by chemical modification at a molecular level of zirconium propoxide with acetoacetoxyethylmethacrylate(AAEM),and then copolymerized with vinyl monomer to form uniform-size hybrid nanoparticles with diameter of around 250nm.Where the AAEM molecule plays the dual roles:(â…°) of providing chelating bonds for combining with Zr(OPr)₄ that could control the hydrolysis rate of Zr(OPr)₄,and(â…±) of providing double bonds for copolymerizing with the other vinyl monomer in the formation of an organic shell.The chemical bonds between organic and inorganic materials were formed and the thermal stability of ZrO₂/PAAEM/PS nanoparticles were enhanced.This study developed a facile and effective approach to prepare the core-shell ZrO₂/PAAEM/PS nanoparticles,and the hydrolysis and condensation of zirconium propoxide could be controlled readily.Core-shell ZrO₂/PAAEM/PS nanoparticles used as lubrication additives exhibits the good properties of friction reducing and antiwear.It should attributed to the repairing effects of nanoparticles on the friction couples.The application of this nanoparticles would provides evidence for the development of high-end lubrication.3.Preparation of ZrO₂/polyoxymethylene(POM) nanocomposites via blending method. Modification of POM is very essentially because its big molding shrinkage,residual strain in produce,notch brittleness etc.POM with different contents of ZrO₂ nanoparticles which were grafted by Polymethylmethacrylate(PMMA) were prepared.The effect of modified ZrO₂ on the crystallization properties of POM were investigated.The results show that the modified ZrO₂ nanoparticles acted as the nucleation agent in POM matrix and decreased the crystallite size of POM, increased the crystal growth rate.The tensile strength and the impact strength of POM were improved simultaneously at a small addition of the modified ZrO₂ nanoparticles.The tribological performance with different contents of ZrO₂ nanoparticles were studied,and indicated that plastic deformation and peeling off of POM were turned mild when modified ZrO₂ nanoparticles added in. The wear resistance of ZrO₂/POM nanocomposites was enhanced and its friction coefficient was changed a little.It can be believed that the rigid ZrO₂ powder increase the rigidity and deformation resistance of POM,so the carry-loading ability of polymers were enhanced during the friction process.The second,nanometer ZrO₂ particles usually located in the stress concentration point in the POM matrix,and can initiate much craze to resist the plastic deformation and adhesion transfer of the resin.Furthermore the nanometer particles combined the resin so intensely that ZrO₂ nanoparticles were not easy to be took off from the POM matrix,the large number of abrasive wear might be avoided.This study enrich the tribology of polymer.4.Preparation of intercalated POM/MoS₂ nanocomposites and study on its crystallization kinetics and tribological properties.Intercalated POM/MoS₂ nanocomposites were prepared by in situ intercalation/polymerization.The XRD pattern showed that the polymer was inserted into the MoS₂ galleries,and the interlayer spacing of the intercalated phase increased from 0.613nm to 1.118nm.The TEM image displayed that MoS₂ has good dispersion in the polymer matrix,and still had a layered structure.The intercalation mechanism of POM into MoS₂ were deduced combination the XRD research with the morphology observation.The crystallization kinetics of POM and intercalated POM/MoS₂ nanocomposites were also analyzed.It was indicated that MoS₂ has a heterogeneous nucleating effect,which enhance the crystallization temperature and crystal growth rate.The tribological behavior of POM/MoS₂ nanocomposites was researched under dry friction,and the worn surfaces were observed.It shows that POM/MoS₂ nanocomposites presented better friction reduction and wear resistance,especially under high load.The ultra-fining of MoS₂ can be achieved by means of this intercalated polymerization method.