Photodegradation of poly

The chemistry of the oxidative and nonoxidative photodegradation of poly(vinyl chloride) is reviewed with emphasis on work that has been published since the early 1970 s. Topics covered include the nature of the photoinitiating species, the photoinitiation mechanism, and the structural consequences and reaction mechanism of the overall photodegradation process. Also included is a summary of recent studies on the determination of structural defects in poly(vinyl chloride) by carbon-13 NMR. 

Photophysical Processes and Photodegradation of Poly(ethylene terephthalate-co-2,6-naphtha1enedi carboxyl ate) Copolymers. We have recently reported the photophysical processes and the photo-degradative behavior of Doly(ethylene terephthalate-co-2,6-naphthalenedicarboxyl ate), PET-2,6-ND, copolymer yarns containing 0.5 - 4.0 mole percent 2,6-naphthalenedicarboxyl ate, 2,6-ND (1) and the parent naphthalenedicarboxyl ate monomer, Figure 3 and 4. 

Photodegradation of Poly(Ethylene Terephthalate) and Poly(Ethylene/1,4-Cyclohexylenedimethylene Terephthalate)... 

In this connection Ishikawa and coworkers studied the photodegradation of poly(disilanylene)phenylenes 203126, and found that irradiation under the same conditions as in the photolysis of the aryldisilanes results in the formation of another type of nonrearranged silene 204 produced together with silane 205 from homolytic scission of a silicon-silicon bond, followed by disproportionation of the resulting silyl radicals 206 to 204 and 205 (equation 51). 

UV irradiation causes photodegradation of poly[methylcyclohexyl-co-methyl((3-tri-methylsilyl)ethyl]silane and PMPS solutions.104 It was found that branching of PMPS is induced by light exposure. The photochemistry of both pure solids and their toluene solutions has been studied. The UV absorption of the copolymer in solution has a maximum at 308 nm and at 303 nm for the... 

An ESR Study of Initially Formed Intermediates in the Photodegradation of Poly(vinyl chloride)... 

The lack of basic understanding and the prevalence of conflicting results in the area of photodegradation of poly(vinyl chloride) is mostly due to the deficiency in fundamental information about the sequence of events that takes place after the polymer molecule absorbs a photon. The use of PVC samples containing foreign unknown substances and the attribution of anomalies and discrepancies in experimental results to impurities further created considerable confusion in this subject. At the present stage of development in the field of photodegradation of PVC, it is critical to establish for pure PVC the identities and dynamics of the intermediates involved. 

In summary, our study of the photodegradation of poly(vinyl chloride) have established the following radical intermediates ... 

Taking into account [81,82] that photodegradation of poly(4,4-dimethyl-l-penten-3-one) [poly(BVK)] and poly(3-methyl-3-buten-2-one) [poly(MIK)] proceeds predominantly through a Norrish type I mechanism via the triplet state (Scheme 15), the above homopolymers have been studied as initiators in the photoinduced polymerization of vinyl monomers such as MMA, St, AN and VAc [83]. 

The photodegradation of poly 1,4-bis ( chloroethylmethylsilyl)benzene involves scission of the silicon-silicon bonds followed by the formation of silicon-carbon unsaturated compounds and hydro-... 

Skowronski, T.A. Rabek, J.F. Ranby, B. The role of commercial pigments in the photodegradation of poly (Vinyl Chloride) (PVC). Polym. Degrad. Stab. 1984, 8, 37-53. 

Shimoyama and coworkers " reported a NIR analysis of photodegradation of poly(methyl methacrylate) using an in situ fiber optic device. This type of technology from a related discipline is notable as a potential application for pharmaceutical systems. 

The dielectric strength of polyethylene has been measured as a function of additive concentration while in stabilised polymers the depth of degradation was found to be uniform . HALS have been found to be effective stabilisers for UV cured coatings and do not influence the cure rate . Bleached wood pulps can be effectively stabilised by ascorbic acid and wool by hydroxy-benzotriazoles and HALS . Hydroxybenzotriazole stabilisers also protect wood pulp and polyurethanes by co-reaction . The spectroscopic properties of monomeric and polymeric benzotriazoles have also been compared . UV absorbers are effective in clear coats and when grafted to wood . Dihydroxybenzophenone stabilisers inhibit the chain scission in the photodegradation of poly(methoxyacrylophenone) while tin stabilisers have also been found to photostabilise PVC . 

The photodegradation of poly(2,6-dimethyl-l,4-phenylene oxide), 1, has received considerable attention both in industrial and in academic laboratories. Workers have observed that when poly-(phenylene oxide) films are exposed to light of wavelengths greater than 300 nm in the presence of oxygen, considerable discoloration and crosslinking occur accompanied by the appearance of carbonyl and hydroxyl bands in the infrared spectrum (2-5). Most workers in the field have ascribed these results to a hydroperoxide-mediated free radical oxidation of the benzylic methyl groups (Scheme I). 

ESR investigation indicates that the radical resulting from scission of the methyl side group is formed on irradiation of a highly concentrated glassy solution of poly-a-methylstyrene [43]. One can thus conclude that the following reactions are more likely to occur as the initial steps of the photodegradation of poly-a-methylstyrene ... 

Ouchi, 1., Hosoi, M. and Matsumoto, F., Photodegradation of poly(ethylene-2,6-naphthalate) films, J. Appl. Polym. ScL, 20, 1983-1987 (1976). 

Poly(alkyl and aromatic ethers) - Organic acids accelerate the photodegradation of poly(isobutylene oxide) while epoxy glass fiber composites can be... 

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