 Nubicoat HWR is manufactured with a newly developed silica encapsulation technology to prevent from acids attacking the polysulfured chromophores of the Ultramarine Blue structure. If this attack happens then the unique blue color fades since the chromophore disappears. The new manufacturing technology is based on the encapsulation of elemental particles rather than the encapsulation of agglomerates. A thinner silica layer is deposited therefore on each Ultramarine Blue particle. This results in the encapsulated pigment having a smaller average particle size as well as a narrower particle size distribution. Moreover it provides higher abrasion resistance of the protective silica coating. When could any Ultramarine Blue incorporated into a coating potentially be exposed to acids? Mostly in the case the coating is exposed outdoors. On one hand, exterior coatings are subjected to UV radiation, high temperatures, water (both humidity and rainfall) and oxygen for long periods of time. Even in the case of using the most stable organic binders they will progressively degrade in the presence of such conditions. This degradation might generate acid radicals that could be released from the binder and attack the Ultramarine Blue structure. On the other hand, when exterior coatings are located in highly industrial areas they can be exposed to the “acid-rain” impact, hence:
This “acid rain” could then lead to the decoloration of Ultramarine Blue used in paints located in such environments. In addition to all these, any coating made with binders of acid-nature e.g. PVDF, PVC plastisols or containing acid additives is likely to have in its composition small traces of acid components that could equally cause the color fading of Ultramarine Blue.
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