Preparation And Study On The Properties Of Novel Wear-resistant Epoxy Resin Composite Materials

Composites are among the most rapidly growing classes of materials,which present a great potential in optimisation of material performance by combining the advantages of several different constituent materials.In particular,polymer-based composites are taking the place of metal materials and becoming the most promising materials in the 21 st century owing to their excellent properties such as light weight,high corrosion resistance,good thermal stability and easy machining.Epoxy resin(EP),one of the most important thermosetting matrixes of advanced engineering composites,has characteristics of good stiffness,low curing shrinkage,high chemical corrosion resistance,and outstanding dimensional stability.However,due to the brittleness and poor properties of heat transfer and wear resistance of pure EP,combining epoxy resin with reinforcements is necessary in order to meet more demanding applications.In this paper,improving the wear resistance and mechanical properties of the epoxy-based composites is the main research object.The investigation mainly focuses on material modification,characterization analysis,mechanical reinforcing and anti-wear reinforcing around the scientific problems such as surface,interface and relations between composition-microstructure-performance.Multiple compound modification methods,for example,three-dimensional reinforcement filling,organic blend and fiber reinforcing are applied to improve the wear resistance and mechanical properties of the epoxy-based composites.Main research contents and conclusions of the thesis are listed as followings:(1)Three-dimensional(3D)interpenetrating network structure epoxy composites are fabricated based on the polydopamine functionalized carbon nanotube(CNT-PDA)reinforced flexible polyurethane(PU)sponge.The CNT-PDA and modified PU sponge are analyzed by by scanning transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR)and scanning electron microscope(SEM).The heat resistance,mechanical properties and friction and wear performance of pure EP,PU3D/EP and CNT-PDA/PU3D/EP composites are comparatively investigated.Results indicate that CNT-PDA is successfully anchored on the skeleton surfaces of sponge via the oxidative self-polymerization of dopamine,forming a continuous 3D carbon network.The interfacial interaction between modified PU sponge and epoxy(EP)matrix is significantly enhanced due to the covalent linkage of PDA.Therefore,CNT-PDA/PU3D/EP composites show the excellent properties.The thermal stability improves as compared to pure EP,and relative to thePU3D/EP composites,the tensile strength and impact strength increase 12.7% and 8.8%respectively.Moreover,as compared with pure EP and PU3D/EP composites,CNT-PDA/PU3D/EP composites exhibite lower wear rate and friction coefficient,and the curve variation trend is more smoothly.In particular,the wear resistance of CNT-PDA/PU3D/EP composites is 6.2 times and 3 times higher than those of pure EP and PU3D/EP composites under the applied load of 1.6 MPa,respectively.(2)Epoxy(EP)composites filling with different contents of polyvinylidene fluoride(PVDF)and carbon nanotubes(CNTs)are fabricated by the solvent evaporation and curing method.FT-IR and XRD analysis are performed to explore the discolorment mechanism of PVDF/EP composites before and after curing.The effects of PVDF and CNTs content on mechanical and tribological properties of composites are investigated.Results reveal that when the mass fractions of PVDF and CNTs are 30% and 1.0% respectively,the composites obtain the best mechanical properties and tribological performance.1.0%CNT/30%PVDF/EP composites exhibite 36.2% and 10.1% increase in flexural strength and hardness,as compared to those of 30%PVDF/EP composites.The wear rate of 1.0%CNT/30%PVDF/EP composites is 92.1% and 40% lower than those of pristine EP and 30%PVDF/EP composites under 1.0MPa and 0.76 m/s,respectively.In addition,wear tests under various applied loads and velocities are conducted for these three kinds of material,and 1.0%CNT/30%PVDF/EP composites show the most excellent tribological performance.The worn and counterpart surfaces are both investigated by the observations of SEM-EDS.During the friction process,the PVDF or CNTs peeled off from the worn surface would form a solid transfer film gradually under the mechanical load,which could effectively protect the worn surface from direct abrasion during the wear testing.This makes a great contribution to the improvement of antifriction wear-resisting performance of 1.0%CNT/30%PVDF/EP composites.(3)A fiber reinforced epoxy-based superhydrophobic coating with long-lived wear resistance is successfully prepared by integrating the hydrophobization of cotton fiber fabric and the curing of epoxy composites consisting of polyurethane(PU),polyfluoroalkoxy(PFA)and hydrophobic SiO2 nanoparticles.FT-IR and SEM analyses are employed to investigate the chemical compositions and micro-morphologies of the modified cotton fiber fabric and the final coating.The influences of PFA and PU contents on the hydrophobic and tribological properties of coating are investigated,and the adhesive force and resistance to acid and alkali tests are carried out at the same time.The role of each epoxy solution component in the properties of coating is also comparatively analyzed.When the epoxy solution containing 35 wt.% PFA and 25 wt.% PU,the obtained coating exhibites superhydrophobic behavior with a water contact angle(WCA)of 153.5 ± 1°.Tribological tests indicate that this fiber fabric/epoxy composites coating has stable friction coefficient and excellent wear-resistanceunder the harsh conditions with the applied load of 2.8 MPa and the sliding velocity of 0.51m/s.After 240000 cycles of abrasion,the coating just showes the decrease in thickness of 80?m without apparent damage and could retain high hydrophobicity with the WCA of 142°.Simultaneously,the coating exhibits good adhesion behavior and is resistant to the acid or alkali solution.The integrated performance of coating is derived from the synergistic action of each composition in epoxy solution.The PFA contributes to lowering the surface free energy,while the hydrophobic silica nanoparticles assist in forming a hierarchical nano/microstructure to increase the surface roughness,and the combination of both endows the coating superhydrophobicity performance.The addition of PU to epoxy solution significantly improves the wear-resistance of coating.