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Silicates > as inorganic flame retardant

BTC offers silicate solutions of alkali metals which are added to certain formulations to increase the heat resistance. Thus, sodium and potassium silicates are well known inorganic flame retardants used in diverse applications which require fire-resistance like

  • fire-resistant doors,
  • fire-resistant glass.

Silicates are also known as water glass or liquid glass. Silicate solutions of alkali metals are known mainly as sodium silicate or potassium silicate. Mainly alkali silicates provide alkalinity beside other properties like adhesion (binding) or stabilisation. The silicate composition and the used alkali metal (sodium, potassium or others) determine the final property of the silicate.



Sodium Silicate

Potassium Silicate

Properties of our silicates as inorganic flame retardant

Alkali silicates are characterized by their weight ratio of xSiO2:yAlk2O (silica:alkali-metal ratio), which is often documented as molar ratio, or water glass modul. The final BTC silicate products depend on the alkali silicate lumps as base material and the further processing to get the final aqueous silicate solution.

Depending on the used molar weight and water content the silicate solutions are different in viscosity, density and pH-value. Generally all silicates are considered as alkaline (pH >9) solutions. With increasing alkali metal content the pH value increases and the adhesion and binding properties are also enhanced.

Potassium silicates differ in the following properties from sodium silicates:

  • they provide less tackiness;
  • no-efflorescence occurs;
  • they show good solubility;
  • they offer high temperature binding properties.

However sodium silicates solutions are economically more attractive if not specific properties like flame colour or no-efflorescence is needed.

Both, aqueous potassium and sodium silicates, are

  • purely inorganic (inorganic silica-polymer solution);
  • non-combustible;
  • VOC-free;
  • odourless;
  • UV-light, thermal and chemical resistant;
  • non-toxicological (they show no allergenic or mutagenic potential);
  • food-contact approved;
  • free of preservatives.

Silicate solutions are sustainable products and thus they are used in many versatile applications.

Despite standard grades like potassium or sodium silicates a special alkali silicate solution is available under the brand name Grossil®.

Applications of our silicates as inorganic flame retardant

Soluble silicates solutions are inorganic products which are incombustible and do not decompose at higher temperature. This key-property is used in versatile applications to enhance the heat resistance. For example, fire protection-glass or doors having a silica layer can resist a longer time in an area of high temperature. The time of resistance is crucial for achieving a certain fire-resistance class.

Welding electrodes (welding-rods) often contain a soluble silicate solution as binding and coating additive. Using potassium silicates or Grossil® products as ingredient for a welding rod produce a transparent violet flame colour during the welding operation. This colour is more convenient for the welder, than the intense yellow caused by sodium silicates.

Soluble silicates are used for the manufacturing of fire-proofed sealing binder or mortar.

Polymer materials with improved flame-retardant properties are obtained using silicates. Such hybrids, organic-inorganic material, show excellent flame-retardant properties. For example, polyisocyanate - sodium silicate solutions in various mixed ratios. See also ‘Flame-retardant properties of sodium silicate/polyisocyanate organic-inorganic hybrid material’ written by Jia-Ji Cheng, Fu-Bao Zhou, published in 2016, April 26th.

Further products used in combination with our silicates

Explore also our

About BTC

BTC Europe is BASF's European sales organization for small and medium-sized customers focused on specialty chemicals. Our silicates are used in a variety of industries as

besides others.