Photostabilization of polyolefins

Photoantioxidants are typified by the class of HAS which although were developed for photostabilization of polyolefins, also possess thermal antioxidant properties. They are generally assumed to function as primary antioxidants in that they scavenge radicals and in particular, peroxy radicals. 

Al-Malaika, S. Scott, G. Photostabilization of polyolefins. In Degradation and Stabilisation of Polyolefins Allen, N.S., Ed. Applied Science London, 1983 283-335. 

Gugumus F. Mechanisms and kinetics of photostabilization of polyolefins with N-methylated HALS. Polym Degrad Stab 1991 34 (l-3) 205-241. 

Of the alkoxy derivatives, 2-hydroxy-4-methoxybenzophenone (ciasorb UV-9), the 4-octoxy- (ciasorb UV-531) and 4-dodecyloxy-derivatives are finding industrial use for the stabilization of polsmiers. The latter are especially recommended for the photostabilization of polyolefins, since, thanks to the presence of a long hydrocarbon chain, they possess good compatibility with the polymers and do not migrate to the surface. 

Gugumus F. Mechanism and kinetics of photostabilization of polyolefins with HALS. An-gew Makromol Chem 1990 176/177 241-81. 

Some dyes remarkably improve the photostabilization of polyolefins when light-stable materials are desired, the choice between black and... 

Al-Malaika S and Scott G, Photostabilization of polyolefins in AUen N S, Degradation and Stabilization of Polyoleftns, London, Applied Science, 283-333, 1983. 

It is well known that HALS compounds (sterically hindered amine light stabilizers) exert excellent photostabilizing effect on polyolefins (1-3). Most of the authors agree that N-oxyl radicals formed from HALS compounds play an important role in the photostabilizing process (4-6). 

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. ... 

It has been shown in the preceding sections that raw polymers are highly susceptible to degradative oxidation. The success of plastic materials, which find apphca-tions in practically any aspect of life, relies heavily on the performance of polymer stabilizers, 70% of which are used for polyolefins. According to their principal protection activity, common polymer stabilizers are conventionally classified as antioxidants, photoantioxidants, photostabilizers, metal deactivators, antiozonants, and heat stabilizers for PVC. 

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