| The phosphate adhesive possesses numerous good properties,however,its water resistance is relatively poor.In this paper,fillers which could react with the matrix were introduced to form the undissolved phase or improve the compactness of the adhesive,so as to improve the water resistance of the adhesive.Water resistance of four kinds of adhesive with Al（OH）3and H3PO4as the matrix was studied,and the fillers were composed of Si,CuO,MgO,SPS and B4C.Firstly,after being soaked in water,the shear strength of the joint bonded by AP+Si+CuO and heated from 150oC to 700oC decreased.According to the XRD and ICP tests,the Al（HP2O7）·2.5H2O was dissolved when the adhesive was soaked in water,which caused that the bonding performance of the adhesive weakened.Secondly,by introducing MgO into the adhesive of AP+Si+CuO,the water resistance of adhesive was improved.And the formation of the Mg3（PO4）2which is difficult to dissolve in water is the reason that the water resistance of the adhesive was improved.And then,the SPS was added into the adhesive of AP+Si+CuO+MgO.Compared to the unmodified adhesive,when heated at 500oC and 700oC,the shear strength reduction rate of modified adhesive soaked in water decreased from 11.53%to 6.70%,which means the water resistance was improved.And it is attributed to the SPS which could improve the density of the adhesive when heated at 500oC and700oC.In the last,another attempt was introducing B4C into the adhesive of AP+Si+CuO+MgO.After being heated from 150oC to 700oC and soaked in water for7 days,the shear strength of the joint bonded by the adhesive of AP+Si+CuO+MgO+B4C was 12.45MPa,10.29MPa,9.93MPa and 10.07MPa.Compared to the unmodified one,the shear strength reduction rate of the joint bonded by the adhesive of AP+Si+CuO+MgO+B4C and heated at 500oC and 700oC increased by 13.61%and 12.4%respectively.And it turned out that it was the oxidation of B4C and formation of B2O3that improved the water resistance of the adhesive. |
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