Photooxidation of polymers

Gugumus F (1990) Photooxidation of polymers and its inhibition. In Oxidation inhibition in organic materials, Vol II, Pospftil J and Klemchuk P (Eds), CRC Press Boca Raton, pp 29-162. 

To avoid interference by products formed in secondary reactions during photooxidation, it is necessary to observe the changes as near the beginning of the process as possible. In this report, we will show that contact angle measurements and other analytical methods which are restricted in application to the surface layers are well-suited to the early detection and study of the photooxidation of polymer surfaces. 

Oxidation of the styrene moiety and changes in the nitrogen environment in benzotriazole took place in 94. Available data confirm that the surface photooxidation of polymers containing aromatic moieties can differ from that of the bulk material [86]. This is due to the higher partial pressure of oxygen and incident photon flux in the surface area. Transmission IR data indicate that the quenching capabilities of benzotriazole moieties in the copolymer 94 are not active in inhibiting surface oxidation. 

Photodegradation and Photooxidation of Polymers Several reviews have appeared covering general as well as specific... 

BANBY AND RABEK Photooxidation of Polymers by Singlet Oxygen 393... 

HANBY AND RABEK Photooxidation of Polymers by Singlet Oxygen 397 substitued phenols by singlet oxygen (57-4l) ... 

On the more commercial front, the photooxidation of polymers continues to attract attention with a continued special interest in natural materials. Bio- and photodegradable plastics are important for agricultural usage. The same applies to polymer stabilisation where commercial applications dominate significantly with much emphasis on the synergistic behaviour of stabilisers. For dyes and pigments stability continues to be of major concern. 

There was undertaken an attempt [12] to show, by methods of luminescence, luminescence centres in PA, intensity of which does not depend on the light intensity, causing photooxidation of polymer. Corrected spectra of PCA fluorescence are characterized by... 

Majority of dispersed dyes, used for PETP dyeing, are instable themselves [284, 286]. That is why it may be supposed that increase of dye concentration leads to accumulation of being formed radicals in the thin surface layer of the sample without mixing, as a result of which the rate of chain break rises and suppresses chain photooxidation of polymer. This effect was called by the authors [175] effect of concentration inhibition, which was observed in the case of polycaproamide light stabilization by action dyes. 

Alessi, S., Calderaro, E., Fuochi, P. et al. (2005) Nucl. Instrum. Methods Phys. Res. B, 236, 55-60. Allen, N. S. Owen, E.D. (1989a) Luminescence studies of the photooxidation of polymers, in Zlatkevitch, L. (Ed.) Luminescence Techniques in Solid State Polymer Research, New York Marcel Dekker. 

PHQTODEGRADATION AND PHOTOOXIDATION OF POLYMERS This continues to be an active area of industrial and academic research with much emphasis on the mechanistic nature of the photochemical processes involved. Such processes are now more readily understood as polymeric systems become more amenable to analysis by modern methodologies. 

Our interest in polymer photodegradation has led us to an investigation of the competition for migrating energy by chain impurities and "defects" such as excimer-forming sites. To isolate the intrachain phenomena, photooxidation of polymer solutions in dimethoxymethane have been carried out. As an example of a very photostable excimer-forming polymer, PS has been selected. Since poly(methyl methacrylate) (PMMA) is known to be far less stable than PS on a quanta-absorbed basis, MMA units have been incorporated into the chain to act as weak links. For energy sinks, 1-VN and 2-VN units have been made part of the chain. 

This chapter reports the results of the literature that concerns the photooxidation of polymer nanocomposites. The published studies concern various polymers (PP, epoxy, ethylene-propylene-diene monomer (EPDM), PS, and so on) and different nanofillers such as organomontmorillonite or layered double hydroxides (LDH) were investigated. It is worthy to note that a specific attention was given to the interactions with various kinds of stabilizers and their efficiency to protect the polymer. One of the main objectives was to understand the influence of the nanofiller on the oxidation mechanism of the polymer and on the ageing of the nanocomposite material. Depending on the types of nanocomposite that were studied, the influence of several parameters such as morphology, processing conditions, and nature of the nanofiller was examined. 

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