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Sunday, 22 September 2019


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Friday 01 September 2000 1:00:00 am

Can anyone help me to determine the way by which UV-light contributes to colourfading of Tc paints?

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Monday 30 October 2000 1:00:00 am

Thermochromic paints are regarded as special products in the coatings sector; their formulation does not contain the usual range of starting materials and formulators rely on individual batches.
Thermochromic materials generally exhibit a certain instability in their molecular structure. Isomerisation occurs under the influence of heat, which is accompanied by a relatively pronounced change in colour. In coating materials formulated according to this principle, both the inorganic components, i.e. special pigments, and the organic substance forming the binder, can be crucial for the thermochromic effect.
A simultaneous colour change due to the effect of light is normally undesirable, at least if it is irreversible. Although this phenomenon can be caused by light of all wave lengths, the risk of reduced thermochromicity is naturally greatest with energy-rich UV radiation.
The inorganic components prove to be least susceptible in this regard, if used at all in the formulation. In pigment-free systems - which are perfectly possible - thermochromicity is solely a feature of organic components. The thermally initiated rearrangement is of a stereochemical nature, for example, on bulky aromatic substituents. Those products in which the isomers have a bonding structure with unchangeable absorption conditions are the most stable against the effects of UV and UV-induced fading. Moreover, the requirements to be met by these products and the potential for using light stabilisers are not fundamentally different to the requirements to be met by light-fast binders in general.

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