Sodium silicate(water glass) is the most widely used binder in investment casting.
The chemical expression is: Na2 ·SiO·H2O.
It is mixed by quartz sand with soda or thenardite, hybrid heating reaction and comes out of sodium silicate (semi-finished products), then put sodium silicate into boiled water.It is a mixture of many kinds of sodium silicate system, which is still contain a certain amount of free silica.
Sodium silicate is alkaline and its PH value commonly between 11-13.
The process performance is mainly composed of pattern material m and density d for measure.
The higher the M is, it shows that the higher the content of silica in sodium silicate, then, the combination of silicon dioxide and sodium oxide are more unstable, the more fee SiO2，the stronger colloidal properties is; The lower of M, The larger of the sodium silicate basicity.
The density indirect index reflecting the concentration of sodium silicate, commonly used d or r, when the modulus in a certain density, the larger of sodium silicate, the larger of the viscosity.