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UV Absorber Definition & Classification
These additives preferentially take in the incident UV radiation and so protect the polymer from the radiation. UV absorbers don't themselves degrade quickly, however they convert UV energy into harmless levels of heat energy, which are dissipated all through the polymer matrix. UV absorbers are limited in their effectiveness because of the physical limitations of the absorption process, and their ability to soak up is governed by the need for high concentrations of additive and thickness of polymer earlier than ample absorption will happen to retard the photodegradation effectively.
Nevertheless, high concentrations of additive can be uneconomic and technically limited, while many applications (resembling polyolefins) are in very thin sections, reminiscent of film and fiber. Benzophenones are good general-goal UV absorbers for clear polyolefin systems, and will also be utilized in pigmented compounds. Benzotriazoles are used mainly in polystyrene. Each can also be used in polyesters. Concentrations are usually about 0.25-1.zero%
Synonyms of UV absorber
UV absorber agent
UV stabilizer
UV stabilizer agent
ultraviolet absorber agent
ultraviolet light absorber agent
UV Absorber Classification
The primary operate of UV absorbers is to absorb UV radiation within the presence of a chromophore (Ch) found in the polymer, the aim is to filter out the UV light that is dangerous to the polymer earlier than Ch* has had an opportunity of forming. Above all, a UV absorber should function within the 290 and 350 nm range.The purpose of UV absorbers is to soak up harmful UV light and quickly transform it into hurtless heat. Throughout this process, the absorbed energy is transformed into vibrational and rotational energy of the molecule constituents. For UV absorbers to be efficient, it is essential that this process takes place more rapidly than the corresponding response within the substrate, and that neither the UV absorber nor the polymer it is intended to stabilize is damaged during energy conversion. The most important UV absorbers are:
a) 2-(2-hydroxyphenyl)-benzotriazoles
b) 2-hydroxy-benzophenones
c) hydroxyphenyl-s-triazines
d) oxalanilides
Every of these UV absorber groups can be characterized by a typical absorption and transmission spectrum.
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