Light, and weathering

Polymer compositions containing pentaerythritol are also used as secondary heat-, light-, and weather-resistant stabilizers with calcium, zinc, or barium salts, usually as the stearate, as the prime stabilizer. The polymers may be in plastic or fiber form (87—89). 

Additives are needed not only to make resins processable and to improve the properties of the moulded product during use. As the scope of plastics has increased, so has the range of additives for better mechanical properties, resistance to heat, light and weathering, flame retardancy, electrical conductivity, etc. The demands of packaging have produced additive systems to aid the efficient production of film, and have developed the general need for additives which are safe for use in packaging and other applications where there is direct contact with food or drink. 

Only a limited range of nitro, azo and anthraquinone disperse dyes exhibit adequate fastness to dry heat, light and weathering for application on polyester automotive fabrics. The structure of Cl Disperse Yellow 86 was modified to incorporate UV absorbers of the benzophenone, benzotriazole or oxalanilide types into the dye molecule. The derived dyes showed better fastness properties than the parent unsubstituted dye. Positioning of the photostabilising moiety within the dye molecule had little influence on the light fastness obtained, however. Built-in benzophenone residues were more effective than the other two types [177]. Nevertheless, several further monoazo and nitrodiphenylamine disperse dye... 

They can withstand exposure to ozone, ultraviolet light and weathering. They have excellent dielectric properties and are not affected by oils. They get more easily tom than mbber and dissolve in aromatic solvent. 

Lightfastness and weatherfastness of quinacridone pigments (Sec. 3.2) deteriorate in the order 2,9 - 3,10 - 4,11 substitution. It is assumed that decreasing the distance between substituents and NH function disturbs the formation of hydrogen bonds [14] a tendency which culminates in the very poor light and weather resistance of 5,12-N,N -dimethyl quinacridone. 

Very light and weather resistant systems require very long outdoor exposure times. In order to accelerate the testing of pigmented systems, test methods have been developed which simulate outdoor conditions. The evaluation of such a test is not only conveniently accelerated, but the resulting data are easy to reproduce and independent of location, climate, date, and time. 

A number of diarylide yellow pigments are also available in the form of very opaque products with small specific surface areas. These are used to an appreciable extent in Chrome Yellow free paints, in packaging printing inks, and other media. Fastness to light and weather are much improved in opaque varieties, compared to the corresponding transparent types their rheological characteristics are superior. Opaque pigments are not resinated. 

A variety of diarylide yellow pigments are very fast to light and weather - although monoazo yellow and orange pigments are superior in this respect. 

P.Y.129 is not employed in plastics. The type of metal in the stabilizer defines how much of a color change is observed as the chelated metal in the pigment molecule is exchanged. Tin stabilizers produce red complexes, which, like corresponding lead or zinc chelates, respond very poorly to light and weather (see also Sec. 1.6.7). 

Types which feature slightly higher specific surface areas are more transparent and demonstrate somewhat different coloristic properties. Such types are not only tinctorially stronger and more greenish but also somewhat less fast to light and weather than opaque varieties, their flow behavior is less favorable. 

Effect of UV Light and Weather on Plastics and Elastomers, Plastics Design Library, New York, 1994. 

General drawbacks are the innate sensitivity to heat, low temperature, UV, light and weathering (but stabilized grades are marketed), weak impact resistance, poor scratch resistance, low flexibility, creep when the temperature rises, easy combustion with dripping and release of abundant black fumes, electrostatic build-up, some machining difficulties. 

The general drawbacks are sensitivity to heat, UV, light and weathering, requiring efficient protection for outdoor exposure (stabilized grades are marketed) inherent easy combustion, but FR grades are marketed cost (but justified by the performances) creep when the temperature rises sensitivity to attack by some chemicals. 

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