Photo oxidation poly methyl methacrylate

In conclusion, singlet oxygen plays a role in the photo-oxidative degradation of polymers containing olefinic unsaturations. Polymers that do not contain these groups, e.g. poly(vinyl chloride), poly(methyl methacrylate), polystyrene, etc., are unreactive [24]. 

Typical ESC A spectra obtained during photo-oxidation, e.g. poly(methyl methacrylate), are shown in Figure 3.25. From these spectra it is possible to evaluate the rate of polymer oxidation, by the comparison of the intensity of Cis and peaks (Fig. 3.26) [1703]. 

Fig. 3.25. ESCA spectra and core level bands of poly(methyl methacrylate) before and after photo-oxidation at various times [1703]. (Reproduced with permission from [1703] published by Elsevier Science Publishers Ltd, 1981.)...

Polymers exhibit variations in response to incident ultraviolet (UV) light. For example, urea-formaldehyde resins, polytetrafluoroethylene (PTFE), and poly(methyl methacrylate) (PMMA) exhibit significant resistance to photo-oxidation, while polyolefins. 

Blending methyl methacrylate-butadiene-styrene copolymer with poly(vinyl chloride) for instance was shown to decelerate the dehydrochlorination (leading to discoloration). The gel content, surface energy, and the spectroscopic characteristics of the blend was altered by the presence of the seccHid polymer [158]. In ethylene-propylene-diene rubber EPDM where the third monomer is ethylene-2-norbomene (NB), the photo-oxidation rate as measured by the accumulation of typical products such as hydroperoxides, varied linearly with the NB content [159]. The same held true for peroxide-crosslinked compounds of the same EPDM except that the linear relationship was found between the relative carbonyl absorbance on photoxidation and the amoiuit of peroxide used to crosslink the material... 

The stabilization of poly(vinyl chloride) against light has been reviewed by Wirth and Andreas. Detailed mechanistic studies have indicated the importance of peroxides in the process of photo-oxidation. It was suggested that protection could be successfully achieved by exclusion of radiation of A < 380 nm. E.s.r. examination of irradiated samples demonstrated the intervention of peroxides in the mechanisms with the ultimate formation of carbonyl groups which caused chain scission by Norrish cleavage. Photo-oxidation of samples of poly(vinyl chloride) modified by incorporation of acrylonitrile-butadiene-styrene, methyl methacrylate-butadiene-styrene, and methyl methacrylate-acrylonitrile-butadiene-styrene copolymers has been investigated. Discolouration was accelerated by the presence of the modifiers. Thermal pre-treatment accelerated photo-induced decomposition. Mechanical properties were also examined, and scanning electron microscopy showed surface defects due to decomposition of the modifier. ... 

The photodegradation and photo-oxidative degradation of polyacrylonitrile [41, 302, 1200, 1951, 2313] and its copolymers such as poly(acrylonitrile-co-isopropyl ketone) [41], poly(acrylonitrile-co-methyl methacrylate) [820], poly(acrylonitrile-co-2 naphthyl methacrylate [338], poly(acrylonitrile-co-butadiene) [24,2001], poly(acrylonitrile-co-styrene) [232, 747], poly(acrylo-nitrile-co-p-styrene) [232] and poly(a-chloroacrylonitrile-co-methyl methacrylate) [820] have been studied in detail. 

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