Light stabilizers UV absorbers

In supercritical fluid chromatography (SFC), a supercritical fluid, usually carbon dioxide, is used. An SFC column resembles a GC column or a packed LC column. The operating temperature is lower than that in GC, which makes it more suitable for the analysis of thermally labile compounds. Another advantage is that water is not present and this is particularly valuable for the analysis of phosphatic antioxidants. In addition, high molecular mass antioxidants can be analyzed with SFC. SFC and FTIR have been used for the analysis of light stabilizers (UV absorbers) and antioxidants [43]. The eluted compounds were deposited on a KBr window after they had passed through a capillary restrictor. The hmit of detection was aroimd 100 ng. 

Permyl . OFerro/Bedford] Proprietary light stabilizer, uv absorber for polymers (fiberglass-polyester cornigat outdoor panels PVC film for outdom use extruded garden hose cellnlosic eyeglass frames). 

Cyasorb . [Am. Cyanamid] Benzophe-nones light stabilizer/uv absorber for films, coatings, elastomers, and plastics in automotive, greenhouse, con-... 

Uses Light stabilizer, UV absorber for use in polymers (automotive, greenhouse, home siding, solar films and plastics)... 

Costabilizers enhancing light stability UV absorbers (1-3 wt%) (e.g., Tinuvin 400 and 1130 (reactive hydroxyl) and Tinuvin 405 or 928... 

Cyagard, Antioxidants, antistatics, UV light stabilizers, UV absorbers, Cytec Industries Inc. 

Polymers in their raw state are usually technically unsatisfactory in one respect or another, such as their stability to light or heat, or their processability, or flammability, or colour, or opacity, or antistatic characteristics, etc., and they simply could not be used in commercial applications successfully without the incorporation of one or more additives [2] to modify behaviour. The additives are often present at very low concentrations (0.1-3 parts per hundred of resin, by weight) and are called stabilizers, UV absorbers, viscosity modifiers, lubricants, fire retardants, pigments, etc. Fillers may be present at 50 or even 150 parts per hundred of resin, by weight. Thermosetting resins tend to have fewer additives of the kind... 

Uses Light stabilizer, UV light absorber for coatings, plastics Trade Names Containing BLS 292 Eversorb 93... 

Each transparent polymer must be stabilized against light-induced degradation by incorporation by uv stabilizers, uv absorbers should absorb uv light without the formation of free radicals. For commercial purposes, they should absorb under 420 nm, since the maximum sensitivity of many plastics lies between 290 and 360 nm. uv absorbers for cosmetic purposes, however, should absorb under 320 nm, since the human skin shows a sharp maximum sensitivity at 297 nm. 

To act as UV stabilizers, UV absorbers must be present at a finite concentration in order to fully absorb harmful UV light. At practically used concentrations, this means that a finite absorbing thickness is required. In the case of thin films [poly(ethylene) for agricultural use] or fibers (polypropylene fibers) this thickness criterion is not met and UV absorbers offer inadequate UV light protection. 

Ultraviolet Light Stabilization. UV light stabilization is produced by fillers that reflect UV, particularly aluminum flake and Ti02, and by fillers that absorb UV radiation and reduce it to harmless wavelengths, particularly carbon black and zinc oxide (Sec. 5.1.4). 

Antioxidants, light stabilizers, biocides, stabilizers, UV absorbers UV stabilizers... 

The exterior durabiHty of relatively stable coatings can be enhanced by use of additives. Ultraviolet absorbers reduce the absorption of uv by the resins and hence decrease the rate of photodegradation. Eurther improvements can be gained by also adding free-radical trap antioxidants (qv) such as hindered phenols and especially hindered amine light stabilizers (HALS). A discussion of various types of additives is available (113). 

The early recognition of the role of stable nitroxyl free radicals, e.g., 2,2,6,6-tetramethyl-4-oxopiperidine, and their hindered amine precursors, in polymer stabilization soon led to the development of the hindered amine light stabilizer (HALS) class of photoantioxidants. The first HALS, Tinuvin 770, AO-33, (commercialized in 1974) proved to offer much higher UV-stabil-ity to polymers than any conventional UV-stabilizer available at the time such as UV-absorbers, nickel compounds and benzoates. Table 3). 

UV absorbers have been found to be quite effective for stabilization of polymers and are very much in demand. They function by the absorption and harmless dissipation of the sunlight or UV-rich artificial radiation, which would have otherwise initiated degradation of a polymer material. Meyer and Geurhart reported, for the first time in 1945 [10], the use of UV absorber in a polymer. They found that the outdoor life of cellulose acetate film was greatly prolonged by adding phenyl salicylate (salol) [10]. After that, resorcinol monobenzoate, a much more effective absorber, was introduced in 1951 [11] for stabilization of PP, but salol continued to be the only important commercial stabilizer for several years. The 2,4-dihydroxybenzophenone was marketed in 1953, followed shortly by 2-hydroxy-4-methoxybenzophenone and other derivatives. Of the more commonly known UV absorbers, the 2-hydroxybenzophenones, 2-hy-droxy-phenyl-triazines, derivatives of phenol salicylates, its metal chelates, and hindered amine light stabilizers (HALS) are widely used in the polymer industry. 

The UV method performs well in the absence of interferences of other additives or pigments but is liable to be in error owing to interference by highly absorbing impurities that may be present in the sample or in the solvent [56,57]. Commercial erucamides with variable light stability have been analysed by means of SEC-UV (254nm)/RI and UV absorption in MeOH [58]. 

Polyvinyl chloride has been modified by photochemical reactions in order to either produce a conductive polymer or to improve its light-stability. In the first case, the PVC plate was extensively photochlorinated and then degraded by UV exposure in N2. Total dehydrochlorination was achieved by a short Ar+ laser irradiation at 488 nm that leads to a purely carbon polymer which was shown to exhibit an electrical conductivity. In the second case, an epoxy-acrylate resin was coated onto a transparent PVC sheet and crosslinked by UV irradiation in the presence of both a photoinitiator and a UV absorber. This superficial treatment was found to greatly improve the photostability of PVC as well as its surface properties. 

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