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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:


Typical Composite Properties

Thermal Conductivity(ASTM C-177.C-325)
Mean Temp. 250oF (120°C) 0.40 Btu.in/hft2 deg.F(0.058 W/mK)
Mean Temp. 450oF (230°C) 0.56 Btu.in/hft2 deg.F(0.081 W/mK)
Mean Temp. 450oF (350°C) 0.65 Btu.in/h.ft2 deg.F(0.094 W/m.K)
Temperature Limit (ASTM C-447) 1200°F (650°C)
Density (ASTM C-447) 1-16 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/in⊃ (0.52-0.61 N/mm⊃)
Linear Shrinkage (ASTM C-356) Less than 2% at 1200°F(650°C)
Water Absorption Under 10% by volume after 24 hours
Note: Heating the moulded product within the range 300-500oF (150-260°C), 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 2.00 - 2.50 : 1 43 - 50
Liquid Hardeners 2.00 - 2.90 : 1 40 - 45
Solid Hardeners 2.00 - 2.30 : 145 - 50

Setting Agents

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

Gas Carbon dioxide - usually blown through the moulded shape.
Liquid Glycerol Diacetate plus either Glycerol Triacetate or Ethylene Glycol Diacetate
Solid 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
15 - 25%
at 68oF (20oC)
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