Polyethylene photostabilization

High density polyethylene photostabilization induces the same problems as in PP light stabilization, hence the same light stabilizers are used. 

Photodegradation of polyethylene waste can be markedly accelerated via its grafting with acrylamide [98], In contrast, photostabilization of polyethylene and polypropylene can be achieved as a result of the grafting of 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone using gamma radiation [ 147], In this case, the grafted compound acting as a U V stabilizer is chemically bound to the backbone chain of the polymer and its evaporation from the surface can be avoided. 

PVC, polyamides, unsaturated crosslinked polyesters, ABS, and wood . Di- and tri-benzotriazole photostabilizers, such as (874) and (875) are synthesized from 2-nitro-benzenediazonium salts and an excess of 1,3-dihydroxybenzene or 1,3,5-trihydroxybenzene <85Mi 40i-0l>. The dibenzotriazole derivatives (874b and 875b) can be used as polymerizable acrylic UV absorbers <84PB237>. A few or/Ao-urethane and -trimethylsilane substituted 2-phenylbenzotriazoles (876 and 877) show similar photostabilization activity . Weather resistance of low-density polyethylene is improved by the addition of a benzotriazole-type photostabilizer <90M140i-04>. 

Photostabilization processes have not received much attention in the last year other than a multitude of review and specialist industrial articles. These include stabilization of polypropylene fibres, new stabilizer developments, sorting of stabilizers for polyethylene, trends in UV absorbers, hindered piperidines (hindered amine stabilizers (HAS)) for polyacrylics and urethanes, new stabilizers for polyolefins, enhanced service life applications, stabilizer mas-terbatches for polyester, stabilizers for UV cured acrylic overcoats for PVC, ° stabilization of clearcoats and various commercial packages. ... 

N.M. Stark and L.M. Matuana, Ultraviolet weathering of photostabilized wood-flour-filled high-density polyethylene composites. /. Appl. Polym. Sci. 90,2609-2617 (2003). 

Mosnacek, J., Bertoldo, M., Kosa, C., Cappelh, C., Ruggeri, G., Lukac, I., Ciardelh, F. Modification and photostabilization of low density polyethylene film by photodecomposition of various diazo-compounds and methyl azidocarboxylate. Polym. Degrad. Stabil. 92, 849-858 (2007)... 

Stark, N.M. Photodegradation and photostabilization of weathered wood flour filled polyethylene composites. Michigan Technological University (2003)... 

Stark, N.M., Mamana, L.M. Ultraviolet weathering of photostabilized wood-flour-filled high-density polyethylene composites. J. Appl. Polym. Sci. 90(10), 2609-2617 (2003) Bouza, R., Abad, M.J., Barral, L., et al. Efficacy of hindered amines in woodflour-polypropylene composites compatibilized with vinyltrimethoxysilane after accelerated weathering and moisture absorption. J. Appl. Polym. Sci. 120(4), 2017—2026 (2011)... 

Cadmium yellow and cadmium red are also good stabilizers, although other workers find the opposite effect. In recent studies" cadmium yellow was found to be a mild photostabilizer in polyethylene and inhibited the development of both hydroperoxides and carbonyl groups during irradiation. These apparent discrepancies in the literature may well be due to differences in pigment manufacturing history. 

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