silicate composites for high temperature insulation and formed shapes

Portland cement plasters made with Perlite aggregate instead of sand offer many advantages. They are more fire resistant, better insulators, and weigh approximately 60% less than conventional cement and sand plasters. With the addition of fiber reinforcement, superior crack resistance is achieved. In addition, fiber reinforced Perlite cement plaster panels can be safely and easily handled in the field.

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 “water glass.” 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:

    Low Cost
    Inorganic
    Easy to Handle
    Rapid Controlled Set
    High Strength
    Insolubility (when aired)
    Chemical Stability

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.

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.

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.

    Gas Carbon dioxide (usually blown through the molded shape)
    Liquids Glycerol Diacetat plus either
        Glycerol Triacetate
        or
        Ethylene Glycol Diacetat
    Solids
        Solids Calcium silicates – e.g. Portland Cement
        Calcium Sulphate – e.g. gypsum
        Silicides-g.g. Ferrosilicon or Calcium Silicate
        Silicofluorides or fluorosilicates
        Ground metallurgical slab
        Heavy metal salts-e.g. carbonates or phosphates