Ultraviolet screens

The addition of pigments to polymers is a very effective practical method for increasing the resistance to photodegradation. Carbon black is by far the most effective. It has been used for years as a filler in rubber vulcanites, but in thermoplastic materials such as polyolefins it also has a protective effect against photodegradation. This was shown for the first time in 1950 by Wallder et al. [126] they demonstrated that the weathering properties of polyethylene are improved by the addition of about 2% carbon black. The effect is dependent on the degree of dispersion and on the size of the particles. Channel Black (particle size about 30 nm), for instance, is more efficient than Furnace Black (particle size 80 nm). The role of carbon black is not only to prevent the absorp- 

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See Free-radical scavengers, Peroxide decomposers, Quenchers, Ultraviolet absorbers, Ultraviolet screening agents. 

Kolb, C.A. et al.. Effects of natural intensities of visible and ultraviolet radiation on epidermal ultraviolet screening and photosynthesis in grape leaves, Plant Physiol, 127, 863, 2001. 

Dunkle, R. L. and Shasha, B. S., Response of starch-encapsulated Bacillus thuringiensis containing ultraviolet screens to sunlight, Environ. Entomol., 18, 1035, 1989. 

Pentyl ester, C,4H2lN02, padimate A, Escatol 506. 2-Ethylhexyl ester, Ci7Hj,NOj, padimate O, Escalol 507. Glyceryl ester, see Glyceryl p-Aminober zoa te. thera cat Esters as ultraviolet screen. 

Yellow prisms from acetic acid, dec 195 196. therap CAT Ultraviolet screen. 

Dimethylaminobenzoic acid p-Dimethylamino benzoic acid p-N,N-(Dimethyl-amino)benzoic acid N,N-Dimethyl-4-aminoben2oie acid NSC 16696 Solarchem 0. Esters used as ultraviolet screens. Needles mp = 242.5° Xm = 308 nm (e = 25119, EtOH) slightly soluble in EtzO, soluble in EtOH. CasChem ISP Van Dyk Inc. Upo. 

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