| In modern industry,epoxy resin can replace traditional metal materials to make gears,bearings,pulleys,etc.However,due to the three-dimensional cross-linking network structure and high cross-linking density,the friction and wear properties of pure epoxy resin can not meet the requirements of the increasingly developing engineering technology,which limits its application in the field of wear resistance.In this thesis,microcapsules with special"core-shell"structure are used to wrap the core material with lubricating effect,which is applied to the preparation of epoxy resin composites to improve the friction coefficient and other comprehensive properties of epoxy resin composites,so as to adapt to higher environmental requirements.In this thesis,an in-situ polymerization method was used to prepare urea-formaldehyde resin microcapsules and melamine resin microcapsules with white oil as the core material.The influence of emulsifier type,stirring speed,core wall ratio and reaction temperature on the morphology and properties of microcapsules were investigated.Scanning electron microscope(SEM),optical microscope(OM),particle size analyzer,infrared spectrometer(FT-IR),thermogravimetric analyzer(TG)and other testing methods were used to characterize the surface morphology,average particle size,chemical structure and thermal stability of the microcapsule material.Two kinds of microcapsules were added to epoxy resin respectively to investigate the physical and mechanical properties and friction properties of epoxy resin composites.The experimental results show that:Urea formaldehyde resin microcapsules were prepared by in-situ polymerization using white oil as core material,urea and formaldehyde as raw materials.The results showed that the best emulsifier was Tween 80 and Span 80(TS compound emulsifier);with the increase of stirring speed,the particle size of urea formaldehyde resin microcapsules decreased gradually;with the increase of core to wall ratio,the wall thickness of microcapsules gradually decreases,and the content of core material first increases and then decreases;The results showed that the optimal preparation conditions were as follows:TS compound emulsifier concentration was 6%,core-wall ratio was 2:1,p H=3,stirring speed was 400 r/min,curing temperature was 70?,the urea formaldehyde resin microcapsules had smooth surface,spherical shape,uniform particle size distribution,and average particle size was about 39?m.The wall thickness is about 0.9?m.The core material content is about 64.50%,and the thermal stability temperature is 150?.Melamine resin microcapsules were prepared by in-situ polymerization using white oil as core material,melamine and formaldehyde as raw materials.The results showed that the best emulsifier was Tween 80 and Span 80(TS compound emulsifier);with the increase of stirring speed,the particle size of melamine resin microcapsules decreased gradually;with the increase of core to wall ratio,the wall thickness of microcapsules gradually decreases,and the content of core material first increases and then decreases;when the concentration of TS composite emulsifier was 6%,the stirring speed was 400 r/min,the mass ratio of white oil to melamine resin was 2:1,p H=7,and the curing temperature was 80?,the average particle size of melamine resin microcapsules was 43?m.The content of core material is about 62.70%,and the thermal stability temperature is 160?.Compared with urea formaldehyde resin microcapsule,melamine resin microcapsule has rough surface,thicker capsule wall,higher hardness and better sealing performance.Two kinds of microcapsules were added into epoxy resin to prepare microcapsule/epoxy resin composites.The results show that the two microcapsules have good dispersibility in epoxy resin;It can effectively reduce the friction coefficient of epoxy resin composite and improve its wear resistance.When the content of UF resin microcapsule was5%,the friction coefficient of the composite was 0.075,which decreased by 63.79%;The wear rate was 0.53×10-7cm-3/Nm,decreased by 72.8%;When the content of melamine resin microcapsule was 3%,the lowest friction coefficient was 0.065,which decreased by 70.45%;The wear rate was 0.48×10-7cm-3/Nm,decreased by 70.3%.With the increase of microcapsule content,the physical and mechanical properties of epoxy resin composites will gradually decrease. |
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