| Epoxy resin(EP)is a kind of thermosetting resin with stable chemical properties,good electrical insulation properties,strong adhesion and excellent mechanical properties.It is widely used as adhesives,coatings,electronic packaging materials,etc.in aerospace,vehicles,electronic devices,building facilities and many other fields.Tribological properties of the epoxy resin coatings are poor due to the three-dimensional cross-linked network structure of the cured epoxy resin,which could cause the coating to be peeled off during the friction process and eventually causes severe damage to the metal substrate.Therefore,improving the tribological properties of epoxy coatings is an urgent problem to be solved.Addition of nanofillers is a popular method that researchers often use to enhance the tribological properties of epoxy coatings.Boron nitride has stable chemical properties,good mechanical properties,and excellent thermal conductivity.In addition,hexagonal boron nitride(h-BN)shows good self-lubricating properties,which can enhance the friction-reduction effect of epoxy coatings.Cubic boron nitride(c-BN)has high hardness,which can increase the rigidity and the wear resistance of epoxy coatings.Based on the construction of a boron nitride modified epoxy composite coating system,this work systematically investigates the synergistic mechanism of binary boron nitride fillers to enhance tribological properties of epoxy coatings.The tribological properties of epoxy composite coatings modified by c-BN and h-BN binary composite fillers varied with the structural proportion of c-BN and h-BN.The modification of h-BN and c-BN with polydopamine improved its dispersibility in epoxy resins.Boron nitride/epoxy composite coatings were prepared by adjusting the proportions of the binary boron nitride filler with different structure,and tribological properties of the composite coatings were investigated under both of dry friction and seawater conditions.The results showed that the binary boron nitride filler could improve the tribological performances of epoxy composite coatings under both dry friction and seawater conditions.When the content of h-BN with lamellar structure was high,the coefficient of friction(COF)and wear rates of the composite coatings were significantly reduced due to the good self-lubricating effect of h-BN.When the contents of h-BN and c-BN were the same,the hard particles of c-BN entered the friction interface and the COF was increased in the case of dry friction,and the COF did not improve due to that of the friction interface was covered by seawater under seawater condition.When the content of c-BN was high,the wear rates were significantly reduced due to that the c-BN greatly improved the hardness of the composite coatings,but the COF of the coatings still increased under dry friction.In summary,when the content of h-BN with lamellar structure and the content of c-BN with diamond-like structure changed,the self-lubricating effect of h-BN,and the effect of improving the hardness of the composite coating by c-BN,and the effect damage to the friction interface by c-BN particles also changed.Hexagonal boron nitride with different shapes greatly influenced the tribological properties of modified epoxy composite coatings.We modified the hexagonal boron nitride nanosheets(BNNP)and nanospheres(BNNS)with polydopamine,and boron nitride/epoxy composite coatings were prepared.The results showed that both nanosheets and nanospheres could improve the tribological properties of epoxy coatings.The BNNP showed good self-lubricating performance,which reduced the COF and wear rates of the epoxy composite coatings.When the content of BNNP was0.5 wt%,it showed the best tribological performance.When the content increased,the tribological properties of the composite coatings were deteriorated due to the agglomeration of the nanosheets,BNNS could significantly improve the tribological properties of epoxy composite coatings when the content of BNNS was 0.25 wt%.This was because BNNS had a relatively high specific surface area.The interface interaction between BNNS and EP was better.BNNS could enter the friction interface during the friction process,providing a certain degree of rolling friction and BNNS could fill in grooves and wide cracks in the friction interface,which smoothed the friction interface and reduced the COF.However,BNNS particles were easier to agglomerate than BNNP due to the higher specific surface area,affecting the tribological performance of the composite coatings.The wear rates of the composite coatings increased by 135.20% and 139.52% respectively when the content of nanospheres were 0.5 wt% and 0.75 wt%,compared with that of 0.25 wt%. |
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