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Elizabeth Henderson
Product Development Manager ITAC Ltd |
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.
