UV screener

Various UV screeners were also tested for their stabilising activity, including hydroxybenzophenones, aminobenzoates, dyes and carbon black. Only combinations of dyes and carbon black showed any effect, the best being the commercially-available Waxoline Black (Table V). 

The UV absorbers are used to a greater extent with the solution vinyls than with the general-purpose and dispersion resins. This is due to the solution vinyl systems having been used to a greater extent outdoors than any of the other systems. The high color pigment loadings used with solution vinyl often act like UV screeners and protect the vinyl resin from attack. 

Bopp RC. U.V. light stabilizer compositions comprising cyclic aliphatic epoxy, UV screener, and polyalkyldipiperidine (HALS) compounds. U.S. Patent 4843116. June 27,... 

UV iight stabiiizers 4 Limited weatherability of PCs, interactivity of light stabilizers with other additives More outdoor-exposed POs using noninteracting forms of HALS and UV-screeners... 

The terminology used when referring to UV screeners and absorbers (UVAs) sometimes overlaps. UV screeners physically block, reflect, and scatter UV radiation while also absorbing it to some degree, while nonblocking organic UVAs efficiently absorb UV energy and convert it to harmless forms. 

Some authors have deduced that dyes, especially aroylbenzimidazoles, provided they are suitably thermally stable [7, 8], and flnorescence brighteners such as Leucopor EGM [9] can photostabilise PET. Naphthol AS dye intermediates have been patented as UV screeners applicable in aromatic polyesters [10]. 

Outside the chemically resistant layers comes the structural portion, which is designed primarily for strength. The exterior surface of the pipe, again, is rich in resin and usually is opaque. Ultraviolet (UV) screeners should be used in outdoor piping to improve its weather resistance. When chlorine has a relatively high hydrogen content, the barriers to UV and visible radiation can prevent photochemical initiation of the hydrogen-chlorine reaction. 

UV screeners are actually pigments. They render the polymer translucent or opaque and absorb or reflect UV light, thus protecting the polymer. Carbon black... 

The use of UV absorbers as UV screeners is practiced in a multitude of applications, such as simglasses, interocular lenses, auto windshield films, solar control... 

A simple way to evaluate the photostability of a UV screener is to measure the ehange in absorption upon irradiation due to variation in UV absorption of various screeners and in various matrixes. It is necessary to model the degradation process to find a meaningful way to normalize the rate of loss. If one assumed that the rate of photodegradation of a UV screener is proportional to the light flux, then the rate of loss is given by... 

An apparent zero-order kinetics was established for the loss of the screener [22, 56], that can be explained by the high absorbing, nonstirred nature of the system and by the negligible quantum yield at the wavelengths of the low-absorbing tail . The photodegradation of currently available UV screeners occurs at such a rate that most of the screener will be depleted from the surface layers of a coating or in the bulk after only 3-5 y of direct sun exposure or after several thousand hours in an accelerated device. An upper limit on the performance of stabilized materials could be supposed. 

Antioxidants, antistats, fillers, flame retardants, UV screeners, slip agents, metal deactivators, whiteners, pigments, and dye receptors are added to polyolefin powder, chips, or granules prior to fiber manufacture. These additives help to overcome fiber sensitivity to heat, UV radiation, and flame and to improve some other properties. In the melt-in-melt system, PP fiberforming polymers can be mixed with these additives to achieve specific formulations. 

Forsthuber, B., Schaller, C., Griill, G. Evaluation of the photo stabilising efficiency of clear coatings comprising organic UV absoibers and mineral UV screeners on wood surfaces. Wood Sci. Technol. 47, 281-297 (2013)... 

Although the pigment imparted some added benefit to the polymer as a UV screener in the past examples, the pigment itself can fade Figure 6) which may be undesirable. In a case such as this, the addition of a UV absorber can help to prevent pigment fading. 

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