Polyester photodegradation

From what is known of the initial photophysical and photochemical processes involved in polyester photodegradation, it would appear... 

Ikada E. 1997. Photo- and biodegradable polyesters. Photodegradation behaviors of aliphatic polyesters. Journal of Photopolymer Science and Technology 10 265-69. 

Studies in Photophysical and Photodegradation Processes in Aromatic Polyester Yarns... 

Scheme 1 shows the reaction which occurs when an aromatic polyester such as [I] is subjected to UV irradiation (5). The polymer first undergoes main-chain cleavage with subsequent rearrangement to polymer [II] which is photostable and can be used as a thin coating to protect efficiently other substrates which are normally photodegradable. 

The results of Figure 7 demonstrate that CO2 evolution from polyester films can also be measured and offers a convenient way of monitoring the photodegradation of polymers such as polylactones which are of increasing interest because of their biodegradability. However, unlike polyalkenes. 

Since 1971 our department is Involved in study of photodegradation, sensitized photooxidation and photostabilization of polymers. A big effort is made in the study of singlet oxygen oxidation of several important polymers, such as polydienes, poly(vinyl chloride), polystyrene and polyesters, reactions of atomic oxygen and ozone with polydienes and photostabilization of these polymers. 

The effect of several metal substrates have been examined on the photodegradation rate of poly(ethyleneterephthalate). Relative stabilities were in the order Cu > A1 > control polymer > Au > Ag under non-oxidative conditions. Under oxidative conditions only the Cu proved to be a photosensitiser499. No mechanistic explanations were apparent. The effect of new catalyst systems have been examined on the rate of photodegradation of polyester fibres OO, Apparently, whilst the use of Ti, Ge and A1 glycolate catalysts gave lower molecular weight products they proved to be more light stable than those prepared with antimony. Dye stability was also markedly improved. 

Discarded conventional plastics remain in the environment for decades. They block sewers and drains, disfigure the streets, beaches and countryside, and kill wildlife on land, in rivers and oceans. To overcome these problems increasing attention has been paid to the development of degradable plastics (1) starch-based, biodegradable, (2) aliphatic polyesters, biodegradable, (3) photodegradable, and (4) oxo-biodegradable. 

Ikada, E. (1997) Relationship between photodegradability and biodegradability of some ahphatic polyesters. Journal of PhotoPolymer Science and Technology, 10, 265-270. 

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