Expanded perlite granules can be bonded to form rigid shapes for a very wide range of applications. The most suitable binder for many purposes is a liquid sodium silicate similar to traditional "waterglass." The liquid sodium silicates are solutions of water soluble glasses manufactured from varied proportions of Na2C03 and SiO2, providing a wide range of chemical and physical properties.
Sodium silicates are widely used as high temperature adhesives and binders due to the following properties:
Silicate-bonded perlite makes an insulation material which is completely non-flammable, the refractory nature of the bond being a major advantage.
Potassium silicate is sometimes preferred for applications where heat insulation and fire resistance are the main objectives. This material has a slightly higher softening point than its sodium counterpart.
Sodium silicate is widely used as a binder for molding sand in foundries. The technology for perlite/sodium silicate composite manufacture is based largely on this foundry industry experience.
PERLITE/SODIUM SILICATE TECHNOLOGY
A wide range of formulations of perlite, sodium silicate solution and setting agent can be used, together with additives to control setting of the mix. General guidelines are given as a starting point.
SOLUBLE SILICATE GRADES
The choice of grade of sodium silicate solution depends on the application and setting process being used. Generally, a higher silicate to alkali ratio gives faster setting while lower ratios and higher solids contents give greater strength in the finished product.
Information given herein is from sources considered
reliable, but no guarantee of accuracy can be made or liability assumed. Your
supplier may be able to provide you with more precise data. Certain compositions or
processes involving perlite may be the subject of patents.