Polymer UV stabilization

The above presented data may constitute evidence that under model conditions (without presence of polymer) UV stabilizers are adsorbed. It is conceivable that the absorption on filler may potentially play a positive role it may slow down loss of stabilizers due to their migration and volatility. Figure 13.10 gives data on changes in carbonyl absorption during PP photooxidation. Both calcium carbonate and talc reduce the performance of HALS even though these fillers are only used in a very moderate concentration (10%), much lower than in typical products. 

Polymer UV Stabilization HLT Dynstat (h) Time to Visual Appearance of Chalking (h)... 

Sunshine and its UV radiation have a deteriorating effeet on many polymers. UV stabilizers play an important role in plastics for external uses hy counteracting the effects of the sun. UV stabilizers are used in plastic items such as greenhouse film, outdoor furniture, and automotive plastic parts. The amounts added are very small and generally <1%. 

Chemically lubricated homo- polymer uv stabilized homo- polymer UV stabilized, 20% glass-filled homopolymer Extrusion grade homo- polymer EMI shielding (conductive) SheM... 

Properties ASTM Test Method Chemically Lubricated Homo- polymer uv Stabilized Homo- polymer UV Stabilized 20% Glass-Filled Homo-polymer Extrusion Grade Homo- polymer 30% Carbon Fiber 10% PAN Carbon Fiber, 10% PTFE-lilled Copolymer Cast... 

Uv-curable polymers Uv devices Uvilon Uvithane 893 Uv light stabilizers... 

The ESIPT mechanism of phototautomerization allows the employment of types 346 and 347 compounds and their analogs as UV stabilizers useful for synthetic polymers. Such a stabilizer -rapidly converts the energy ab-... 

A multidimensional system using capillary SEC-GC-MS was used for the rapid identification of various polymer additives, including antioxidants, plasticizers, lubricants, flame retardants, waxes and UV stabilizers (12). This technique could be used for additives having broad functionalities and wide volatility ranges. The determination of the additives in polymers was carried out without performing any extensive manual sample pretreatment. In the first step, microcolumn SEC excludes the polymer matrix from the smaller-molecular-size additives. There is a minimal introduction of the polymer into the capillary GC column. Optimization of the pore sizes of the SEC packings was used to enhance the resolution between the polymer and its additives, and smaller pore sizes could be used to exclude more of the polymer... 

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). 

Irg 1076, AO-3 (CB), are used in combination with metal dithiolates, e.g., NiDEC, AO-30 (PD), due to the sensitized photoxidation of dithiolates by the oxidation products of phenols, particularly stilbenequinones (SQ, see reaction 9C) (Table 3). Hindered piperidines exhibit a complex behavior when present in combination with other antioxidants and stabilizers they have to be oxidized initially to the corresponding nitroxyl radical before becoming effective. Consequently, both CB-D and PD antioxidants, which remove alkyl peroxyl radicals and hydroperoxides, respectively, antagonise the UV stabilizing action of this class of compounds (e.g.. Table 3, NiDEC 4- Tin 770). However, since the hindered piperidines themselves are neither melt- nor heat-stabilizers for polymers, they have to be used with conventional antioxidants and stabilizers. 

The photodegradation of synthetic polymers can be considerably reduced upon addition of ultraviolet stabilizers. The UV stabilizers (preferably derivatives of o-hydroxy-benzophenone or of 2-(2 -hydroxys -methylphenyl)benzotriazole (Tinuvin) transform the absorbed light energy into thermal energy thus preventing all sorts of photochemically initiated reactions. For review articles see the papers of Otter-stedt (.l), Heller and Blattmann ( 2, 2), Kloepffer (jl, j ), Gysling (JS) and Trozzolo (19 ) ... 

Is the UV-stabilization only due to the screening effect (or more precisely light absorbing effect in a spectral region where the absorption spectra of polymer and UV-stabilizer overlap) of the UV-stabilizers and/or can it be enhanced by an energy transfer from the excited polymer to the stabilizer molecule ... 

Besides these "physical aspects" of the light protection of polymers there are some hints that UV-stabilizers of the o-hydroxyphenyl-benzotriazole type are able to scavenge radicals ("chemical aspects") the production of which could not be suppressed completely by the methods described in this paper (23). 

The styrenic thermoplastic elastomers are the only type which are fully compounded in the manner of conventional elastomers. In this case, however, the addition of carbon black, or other fillers, does not give reinforcement. Additions of polystyrene, or high impact polystyrene, and oil are used to vary hardness and tear strength, and fillers can be used to cheapen the material. Other added polymers, e g., EVA, can be used to increase ozone resistance. These materials also require antioxidants for protection during processing and service life, and the poor UV stability restricts their use in outdoor applications. 

Allen, N. S., Edge, M., Mohammadian, M. and Jones, K., UV and thermal hydrolytic degradation of poly (ethylene terephthalate) importance of hydroperoxides and benzophenone end groups, Polym. Degrad. Stabil., 41, 191-196 (1993). 

The thermal stability and lightfastness of polyesters is particularly necessary for technical and high-performance applications. The modification of the polymer causes disorder and affects the stability as well as some other properties. PET modified by DEG suffers particularly from photo-oxidative reactions due to the presence of the sensitive ether bonds. These copolymers need special stabilization depending on the kind and degree of modification. The UV stability can also be influenced by the technology of the process, whereby slight improvements of DMT-based polymer are observed [29],... 

As a rule, however, most of the ESIPT dyes exhibit weak to very weak fluorescence quantum yields, i.e., the quantum yield of the nonradiative processes is near unity. Such dyes, if they show little permanent photodestruction, can be used as ultraviolet (UV)-stabilizers of polymers, such as Tinuvin (a hydroxy-benzotria-zole),(45) because they efficiently convert UV radiation, harmful for the polymer, into harmless heat. The mechanisms of these nonradiative decay paths are often linked to... 

Williams, R.S. (1983). Effect of grafted UV stabilizers on wood surface erosion and clear coating performance. Journal of Applied Polymer Science, 28(6), 2093-2103. 

USP acid test analy chem A United States Pharmacopoeia test to determine the carbonizable substances present In petroleum white oils. yti es pe as ad. test) UV stabilizer chem Any chemical compound that, admixed with a thermoplastic resin, selectively absorbs ultraviolet rays used to prevent ultraviolet degradation of polymers. Also known as ultraviolet stabilizer. yu ve sta ba.iTz ar)... 

Uses. Solvent for polymers polymerization catalyst stabilizer against thermal degradation in polystyrene UV stabilizer in polyvinyl and polyolefin resins... 

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