Wednesday, 26 February 2014

How we use Calcium

Elizabeth Henderson
Product Development Manager

This month we’re going to consider calcium - far away to the left on the periodic table from the materials we’ve looked at so far. Calcium exists very widely in nature, as naturally occurring minerals as disparate as marble and chalk. Crystalline mineral Blue John (fluorspar, CaF2) is exploited to make jewellery and ornaments and calcite (CaCO3) is also sometimes found in spectacular natural crystals. However, the materials used by Itac tend to be white powders which have been mined and refined for industrial applications. Calcium’s chemistry is hardly exploited at all in Itac’s systems, but its compounds play a valuable role as fillers and are used in large quantities. Itac’s products are principally solvent-borne, which means that calcium compounds do not dissolve in them at all. In spite of this the particles’ large surface areas and the low surface tension of the solvent mix (compared to water) means that they wet out readily and form stable suspensions.
Calcium carbonate is widely used in Itac’s formulations for building products. Ultrafine calcium carbonate has been shown to improve the tear strength, tensile strength, and modulus of natural rubber latex film – it gives similar improvements in properties to Itac’s gutter paint films. The powder is easily incorporated and does not require remixing when the material has been stored. Calcium carbonate also plays a big part in construction adhesive formulation, by contributing to the rheology of the mix. It raises the viscosity, but the shear-sensitivity of the mix is limited so the product dispenses readily but smoothly and a bead of sealant does not flow out of shape after delivery.
An additional property of calcium materials which could be of interest to Itac is their flame-retardant nature. Calcium sulphate (gypsum) is used to make building products which are intrinsically flame retardant, and we have done some work here to try and use calcium compounds to form a coating which when subjected to high temperatures forms a ceramic-type matrix which would be a non-combustible shield impenetrable to smoke. So far we haven’t succeeded in this, but the idea is valid in the context of calcium chemistry.

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