Ultraviolet stability carbon black pigments

In terms of weatherabilityf polystyrene does not exhibit ultraviolet stability and is not considered we ather-re sis tan t as a clear material. Continuous, long-term exposure results in discoloration and reduction of strength. Improvement in weatherability can be obtained by the addition of ultraviolet absorbers, or by incorporating pigments. The best pigmenting results are obtained with finely dispersed carbon black. 

Ultraviolet Light Stabilizers. Both titanium dioxide and carbon black are strong ultraviolet light absorbers and effective in protecting the PVC. For ultraviolet light absorption in transparent PVC oi foi impiovement of pigmented systems, various derivatives of benzotnazole are used. 

Typical, ultraviolet absorbers are salicylate esters, -amino-benzoate esters, a-cyano-0-phenylcinnamate esters, 2-hydroxybenzo-phenones, 2(2-hydroxyphenyl)2H-benzotriazoles (Figure 1), and more recently diaminodiphenyloxamides. Some pigments and various types of carbon blacks are also known as effective ultraviolet stabilizers. Another mechanism by which the stabilization of the polymers can be accomplished is by quenching the excited state of the molecules. 

Ultraviolet-screening pigments have been used extensively to protect polymers against the harmful effect of uv radiation. For example, carbon black imparts an extraordinary stabilizing power, mainly on account of its high uv-absorbing capacity However, like other UVA, carbon black has additional photoantioxidant... 

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