Condensation and hydrophobicity of the surface hydroxyl groups between organosilane modified water glass and microsilica

As one of the novel green foundry binders, the bonding strength of two-component inorganic binder system (water glass-microsilica) under wet conditions needs to be further improved. In this work, gamma-(methacryloxypropyl) trimethoxy silane (MPS) was added to water glass. The effect of MPS on the storage stability of sand core was studied, based on which the mechanisms of condensation and hydrophobicity of water glass-microsilica were discussed. The results showed that the maximum bonding strength of 1.0 wt% MPS modified sand core was increased by 15.5% at 80-85% RH. MPS promoted the dehydration condensation between water glass and microsilica, which will make its three-dimensional network more complex. Moreover, it formed a hydrophobic organosilane layer on the surface of the bonding bridge, which can play a role in shielding hydrophilic Na+ and prevent the destruction of bonding film by forming Si-O-R bonds, preventing the external water from damaging.