| In the curing process of waterborne epoxy resin(EP),it is easy to produce holes,cracks and other defects,which seriously limits its application in the field of anti-corrosion.In this paper,nano hexagonal boron nitride(h-BN)with high permeability is used as raw material and its surface is modified by chemical modification.Then the modified nano boron nitride/waterborne epoxy composite coatings are prepared to explore the mechanism of modified h-BN.The concrete research content is as follows:(1)Firstly,h-BN is hydroxylated,and then KH-550 reacts with hydroxylated h-BN to obtain KH-550 modified h-BN(KBN)functional filler.The KBN/EP composite coating was prepared.The influences of KBN dispersion and its addition amount on the corrosion behavior waterborne epoxy coating were investigated.The results show that the dispersion of h-BN modified by KH-550 in waterborne epoxy system is better than that of h-BN.The low-frequency impedance of KBN/EP composite coating is 3.8 times higher than that of EP coating and 3.1 times higher than that of BN(1.0 wt%)/EP composite coating.At the same time,the low-frequency impedance value of KBN/EP composite coating decreases with the increase of KBN content,the anti-corrosion performance of the 0.5 wt.%KBN/EP composite coating is the best,and its low-frequency impedance value is 6.73×10~7?·cm~2.(2)On the basis of previous work,in order to further improve the dispersibility of KBN,KBN was carboxylated by succinic anhydride,and then STP modified h-BN(SBN)functional filler was prepared by the reaction of sodium aminotriphosphate(STP)with KBN.Finally,SBN/EP composite coating was prepared.The results of IR and XRD show that STP has been successfully grafted onto the surface of KBN sheet,and the grafting reaction has no effect on the interlayer spacing of nano materials.Meanwhile,compared with KBN,the sodium phosphate group on SBN has stronger water solubility and can be more evenly dispersed in waterborne epoxy system.Electrochemical impedance spectroscopy(EIS)and salt spray test show that the corrosion resistance of SBN/EP composite coating is significantly higher than that of KBN/EP,and the highest low frequency impedance value can reach 1.48×10~8?·cm~2,which is an order of magnitude higher than that of KBN/EP composite coating and pure EP coating. |
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