Polymeric hindered amine light

Set B Based on the results of set A discussed below, a third set. Set B, was prepared (Table IV). Cyasorb 531 (a benzophenone UV light absorber) was found to be the most effective stabilizer in Set A. It was therefore rerun at an even lower add-on in Set B, and since it was the only UV light absorber included in Set A, a second type of UV absorber, Tinuvin 327 (a benzotriazole) was included in Set B. Two new non-polymeric hindered amine light stabilizers (HALS) Tinuvin 770 and Tinuvin 765 were also evaluated in Set B with the hope that they might be more effective than the polymeric HALS (Chimassorb 944LD) included in Set A which was quite detrimental to the heat stability. Combinations of these four additives were also applied in Set B. The three new compounds evaluated have been reported to be effective light stabilizers for polyester and polyamide fibers (Capocci, G., Ciba Geigy Corporation, Ardsley, NY, personal communication, 1986). 

Kimura, K., et al. Direct determination of a polymeric hindered amine light stabilizer in polyproplylene by thermal desorption-gas chromatography assisted by in-line chemical reaction, Analyst, 2000, 125, 465. 

HALS-4 Polymeric hindered amine light stabilizer no... 

Chitnassorb . [Ciba-Geigy/Additives] Polymeric hindered amine light and heat stabilizer for polyolefins. 

Many studies on the identification of polymer additives by Py-GC/MS have been published recently for example, an innovative method based on direct analysis of polymers containing polymeric hindered amine light stabilizers (HALS) by using pyrolysis coupled to GC/MS was applied successfully for fast and straightforward identification of these additives. Each of the HALS showed different pyrolysis gas chromatograms containing characteristic pyrolysis products. As a result, HALS additives with very similar chemical structures, e.g., Chimassorb 944 and Chimassorb 2020, could be distinguished. 

Polymeric hindered amine light stabilizer is excellent for protection against ultraviolet degradation. Applications include polyolefins (polypropylene, polyethylene), olefin copolymers such as EVA as well as blends of polypropylene with elastomers. Also effective in polyacetals, polyamides, polyurethanes, flexible and rigid PVC, and PVC blends. 

A polymer-bound hindered amine light stabilizer [P-HALS] has been synthesized by terminating the living anionic polymerization of isoprene with 4(2,3-epoxy pro-poxy)-1,2,2,6,6-pentamethylpiperidine followed by hydrogenation of the resulting polymer to E-P copolymer using Zeigler type catalyst [40] ... 

Light stabilizers improve the long-term durability of plastics, especially polyolefins. Polymeric hindered amines, such as Tinuvin 622, and Chimasorb 944, are commonly used in polyolefins as light stabilisers. 

The chemical and physical observations here indicate that biological defacement of polymeric materials is a process precipitated by surface changes. This study suggests that polymers in exterior hostile environments can have significantly delayed surface erosion by the incorporation of light stabilizers. Optimal stabilization of the polymer surface with benzotriazoles and/or hindered amine light stabilizers provides the maintenance of surface integrity and thus increases the material s functional lifetime. 

A hindered amine light stabiliser has been found to enhance the light stability of blends of low and linear low density polyethylene with the latter contributing linearly to the overall stability of the blend. In coatings hindered piperidine light stabilisers are also effective especially when used in conjunction with a benzotriazole absorber while surface protection of styrene copolymers with 2-(2-hydroxy-5-vinylphenyl)benzotriazole requires a small amount of a hindered piperidine stabiliser. Polymeric hindered piperidine compounds on the other hand have been found to inhibit the singlet oxygen attack on poly(butadiene). ... 

The second part of this study [92] considered this peculiar point that has considerable consequences in terms of fundamental aspects of both the photooxidation of nanocomposites and the durability of these materials. A special attention was given to the interactions between the antioxidant, the clay (montmorillonite), and the compatibilizing agent (maleic anhydride), in terms of influence of each component on the rate of oxidation of the polymeric matrix. Two kinds of stabilizers were tested a phenolic antioxidant (Scheme 15.14) generally used to process polypropylene and a redox antioxidant of the hindered amine light stabilizer (HALS) class (Scheme 15.15) that is used as long-term stabilizer for polypropylene. 

The early examples were variants or derivatives of piperidine, and have long been used as antioxidants, but it was foimd that some of them were also effective UV stabilisers. Today there are 35 or 40 different hindered amine light stabilisers (HALS) including monomeric, oligomeric and polymeric variants. They are used alone in protecting polyolefins, being particularly effective in polypropylene and HOPE and, although LDPE has provided some difficulties, appropriate HALS stabilisers can still be used. EVA copolymers can use HALS, but styrene polymers often need support from other types of stabiliser such as a benzotriazole, and flexible PVC also benefits from auxiliary stabilisation. 

Keywords photooxidation, UV absorbers (UVA), outdoor performance, weathering, accelerated weathering, kinetic chain length, photoinitiator, Norrish reactions, peroxide decomposer, hindered amine light stabilizers (HALS), photosensitizer, transition metal complex, UV stabilizer, time-controlled stabilization, reactive antioxidants, polymeric antioxidants. 

Of the various chemical classes of UV stabilizers that have been developed, the benzophenone and benzotriazole UV absorbers, the hindered amine light stabilizers (HALS), and their combinations continue to satisfy the UV stabilization requirements of most of the large-volume outdoor polymer applications. In addition, many new stabilizer chemistries, such as UV absorbers based on hydrox-yphenyl triazines, have been developed for more demanding applications or to satisfy specific market needs. Light stabilizers together with other additives (qv), such as antioxidants (qv), impact modifiers, colorants (qv), fillers, heat stabilizers (qv) and plasticizers (qv), have enhanced the properties and extended the service life of polymeric materials, resulting in the replacement of traditional materials in a multitude of outdoor weatherable applications. 

The most common UV absorbers used commercially are hindered amine light stabilizers, which can also function as antioxidants in some plastics. Other UV absorbers include benzotriazoles and benzophenones, salicylate esters, cyanoacrylates, malonates, and benzilidenes. Factors such as the type of polymeric resin, type and level of pigments being used, and the presence of crosslinking compounds and catalysts govern the selection of UV absorber to be used. 

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