Effect of magnesium oxide on the moisture absorption performance of phosphate adhesives

Aluminum phosphate adhesives have the advantages of low curing temperature, non-toxic, high bonding strength and high temperature structural stability, which can bond metals and ceramics, and can also be used as a matrix for refractory materials and composite materials, and have a wide range of applications in the construction and aerospace fields.

In this paper, modified aluminum phosphate adhesive was prepared by using phosphate solution prepared with H_3PO_4 and Al(OH)3 as the base material and

ZnO and MgO as the curing agent. The curing temperature of the adhesive was studied by differential scanning calorimetry (DSC), the structure of the insulation material was analyzed by scanning electron microscopy, and the hygroscopic properties of the phosphate adhesive were studied by comparing the weight gain ratio of each specimen under atmospheric conditions.

The results showed that the addition of ZnO and MgO could reduce the curing temperature of the adhesive and promote the cross-linking curing of the adhesive to different degrees, among which, the addition of 5% (mass fraction) ZnO and 5% (mass fraction) MgO could reduce the curing temperature of the phosphate adhesive from 254℃ to 172℃ and 161℃, respectively. The improvement of hygroscopic properties was more obvious with the addition of curing agent, among which, the addition of 5% (mass fraction) MgO could reduce the percentage of hygroscopic weight gain of the adhesive from 13.5% to 6.3%.