Photodegradation, polymer

Consider the photodegradation of polystyrene in sunlight (Scheme 9.5). Polymer photodegradation can be slowed down by adding photostabilisers, which may be ... 

See for example (a) Pospisil, J. and Klemchuk, P. P., Oxidation Inhibition in Organic Materials, Vol II, CRC Press, New York, 1990 (b) Rabek, J. F Polymer Photodegradation, Mechanisms and Experimental Methods, Chapman Hall, London, 1995 (c) Wypych, G., Handbook of Material Weathering, 2nd Edn, ChemTec Publishing, Ontario, Canada, 1995. 

F. Photodegradation of polymers-. Photodegradation of polymers assumes importance in two different contexts (i) ultraviolet and visible radiations are harmful to biopolymers like DNA, polysaccharides, proteins, etc. and an understanding of their mode of photolysis is important in life processes and (ii) more and more use of plastic materials in everyday life has created a problem of disposal. 

The biphasic kinetics curve for the reactions of polymers is very typical and is found frequently in the polymer literature. Daglen and Tyler showed62 that equation 27 gave excellent fit to these systems as well, which suggests the presence of reaction spheres is common in the mechanism of solid-state polymer photodegradation. 

Rabek, J. F. Polymer Photodegradation Mechanisms and Experimental Methods Chapman and Hall Cambridge, 1995. 

Andrady AL. Wavelength sensitivity in polymer photodegradation. In Andrady AL, Narasimhan B, Pascault J-P, et al., eds. Advances in Polymer Sciences. Vol. 128. New York Springer-Verlag, 1997 49-94. 

Photosensltlzatlon of polymers has been found to be Important for a variety of purposes such as 1) Photopolymerization, 2) PhotomodlfIcatlon (photo-grafting), 3) Photodegradation, and 4) Photostablllzatlon (13 In commercial polymers photodegradation reactions are usually photosensitized by the presence of alien groups In the chain or by the presence of trace Impurities (2,3). 

It has been demonstrated that the sensitivity of the mass spectrometer makes it Ideally suited for application to the study of polymer photodegradation. The basic understanding of the system makes it possible to extract useful kinetic and chemical information about the degradation reactions. Work on the roles of temperature, chemical composition and network structure is in progress. 

Fig. 10 Strain at break Vs. UV exposure time for polypropylene copolymer bars made from (a) virgin polymer (V) (b) virgin polymer + undegraded recyclate (U) (c) virgin polymer + photodegraded recyclate (P). Results for blends with recyclate contents of 10% and 25% are shown. (More details in Craig, I.H. White, J.R. Mechanical properties of photo-degraded recycled photo-degraded polyolefins. J. Mater. Sci. 2006, in press.)...

Interest in polymer photodegradation and oxidation processes is still widespread. Several reviews in this area have... 

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