UV Absorber Definition & Classification
What Is UV Absorber?
(Definition of UV absorber)
These additives preferentially absorb the incident UV radiation and so protect the polymer from the radiation. UV absorbers do not themselves degrade rapidly, but they convert UV energy into harmless levels of heat energy, which are dissipated throughout the polymer matrix. UV absorbers are limited in their effectiveness because of the physical limitations of the absorption process, and their ability to absorb is governed by the need for high concentrations of additive and thickness of polymer before sufficient absorption will occur to retard the photodegradation effectively.
However, high concentrations of additive would be uneconomic and technically limited, while many applications (such as polyolefins) are in very thin sections, such as film and fiber. Benzophenones are good general-purpose UV absorbers for clear polyolefin systems, and can also be used in pigmented compounds. Benzotriazoles are used mainly in polystyrene. Both can also be used in polyesters. Concentrations are usually about 0.25-1.0%
Synonyms of UV absorber
- UV absorber agent
- UV stabilizer
- UV stabilizer agent
- ultraviolet absorber agent
- ultraviolet light absorber agent
UV Absorber Classification
The main function of UV absorbers is to absorb UV radiation in the presence of a chromophore (Ch) found in the polymer, the aim is to filter out the UV light that is harmful to the polymer before Ch* has had a chance of forming. Above all, a UV absorber must function within the 290 and 350 nm range.The purpose of UV absorbers is to absorb harmful UV light and quickly transform it into harmless heat. During this process, the absorbed energy is converted into vibrational and rotational energy of the molecule constituents. For UV absorbers to be effective, it is essential that this process takes place more rapidly than the corresponding reaction 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:
