Pre-formed Insulation Shapes

Silicate bonded perlite can be formed into rigid shapes and makes an insulation material which is conpletely non-flammable. Sodium silicates are widely used as high temperature adhesives and binders. The technology for perlite/sodium composite manufacture is based on the use of solidum silicate as a binder for moulding sand in foundries. Sometimes potassium silicate is preferred for applications where heat insulation and fire resistance are the main objectives as this material has a slightly higher softening point.

Sodium Silicate

Liquid sodium silicate is the most suitable binder for many purposes and is similar to tradiional "waterglass". The liquid sodium silicates are solutions of water soluble glasses manufactured from varied proportions of Na, Co and SiO, 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

Typical Composite Properties

Thermal Conductivity (ASTM C-177.C-325)
Mean Temp. 250^oF (120^oC)	0.40 Btu.in/hft² deg.F (0.058 W/mK)
Mean Temp. 450^oF (230^oC)	0.56 Btu.in/h.ft² deg.F (0.081 W/m.K)
Mean Temp. 660^oF (350^oC)	0.65 Btu.in/h.ft² deg.F (0.094 W/m.K)
Temperature Limit (ASTM C-447)	1200^oF (650^oC)
Density (ASTM C-447)	11-16 lb/ft³ (180-260 kg/m³)
Modules of Rupture (ASTM C-203, C-446) Min.	50-60 lb/in² (0.34-0.41 N/mm²)
Comprehensive Strength (ASTM C-165) Min.	75-88 lb/in² (0.52-0.61 N/mm²)
Linear Shrinkage (ASTM C-356)	Less than 2% at 1200^oF (650^oC)
Water Absorption	Under 10% by volume after 24 hours

Note: Heating the moulded product within the range 300-500^oF (150-260^oC), depending on the formulation, enhances the strength and water resistance of the composite material.

Formulations

A wide range of formulations of perlite/sodium silicate solution and setting agent can be used, together with additives to control the absorbency of the perlite and the speeed of setting 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 whilst lower rations and higher solids contents give greater strength in the finished product.

Setting Process	Silica/Alkali Ratio	Solids Contents
Gas Injection Liquid Hardeners Solid Hardeners	2.00 - 2.50 : 1 2.50 - 2.90 : 1 2.00 - 2.30 : 1	43 - 50 40 - 45 45 - 50

Setting Agents

Gas	Carbon dioxide - usually blown through the moulded shape.
Liquids	Glycerol Diacetate plus either Glycerol Triacetate or Ethylene Glycol Diacetate
Solids	Calcium silicates e.g. Portland Cenent Calcium sulphates e.g. Gypsum Silicides e.g. Ferrodilicon or Calcium Silicide Silicoflourides or Flourosilicates Ground metallurgical slag Heavy metal salts e.g. Carbonates or Phosphates

Suggested formulations using different setting agents
Material*	Gas Setting	Liquid Setting	Solid Setting
Sodium silicate Solution as % by volume of perlite	2.5 - 5%	5 - 10%	5 - 15%
Setting agent as % by weight of sodium silicate	15 - 25% at 68^oF (20^oC)	18 - 24%	25 - 50%

* The amount of silicate needed will depend on the particle size, density and absorbency of the perlite used.

Applications

High Temperature Insulation

Pipe covering
Furnace lining
Industrial ovens/kilns
Domestic oven lining
Firebricks and stoves
Chimney insulation
Foundry moulds and coves
Runner insulation shapes
Refractory Shapes

Building Construction

Ceiling tiles
Acoustical panels
Sandwich panels
Wall insulation blocks
Cyrogenic tank base insulation
Decorative mouldings and shapes
Sprayed coatings
Acid resistant blocks
Roofing tiles

Fire Protection

Fire doors
Fire resistant coatings
Steelwork cladding
Rood truss insulation
Fire-safe cabinets
Document boxes
Computer disk storage boxes
Electrical control cabinets

Other Applications

Liquid waste solidification
Asbestos encapsulation
oil absorbents
Welding rod coatings