Photo-oxidation of poly(vinylbutyral) (original) (raw)
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Photochemical behaviour of poly(vinylmethylether)
Polymer Degradation and Stability, 1998
The photochemical behaviour of poly(vinylmethylether) (PVME) has been studied under irradiation at long wavelengths (A. > 300 mn), at 60°C and in presence of oxygen. In order to identify the photoproducts, the photooxidised samples have be submitted to chemical treatments and to photolysis (in the absence of oxygen). The results of the thermooxidation, at WC, of PVME samples are also reported and compared to photooxidation results. The oxidation kinetic curves were plotted and the nature of the photoproducts as a function of irradiation time was analysed. The FTIR analysis of the oxidation was completed by the analysis of the whole photoproducts by mass spectrometry. A mechanism accounting for the main routes of oxidation is proposed. 0 1998 Elsevier Science Limited. All rights reserved (
Photolysis and photo‐oxidation of unsaturated polyesters
Makromolekulare Chemie. Macromolecular Symposia, 1989
The photolytic and photo‐oxidative evolution of unsaturated polyesters, crosslinked or not, exposed to polychromatic light is studied using IR, FTIR, UV spectrometries. The influence of each elaboration parameter (nature and concentration of diacids like maleic anhydride, fumaric acid or phthalic acids, nature of glycols, nature and concentrations of crosslinking agents, mode of crosslinking) is determined. The mechanism involving primary excitation of the maleate‐fumarate or of phthalate units and radical reactions accounts for the appearance of hydroxylated and carbonylated groups. Photoyellowing of unsaturated polyesters is related either to the styrene oligomers or to the phthalate units. Through parallel studies of photochemistries in polystyrene (PS) and poly(butylene terephthalate) (PBT) at long wavelengths, the different sources of photo‐yellowing are precised.
Polymer Degradation and Stability, 1981
Processing of polystyrene at 160°C for different periods in the closed chamber of a Brabender Plastograph results in no appreciable oxidation. Therefore, the photooxidative stability of the polymer, as measured from retention of the ultimate tensile strength, is not affected by such treatment. On the other hand, acetophenone groups, the concentration of which increases with processing time, are produced at 160°C in the open chamber of the Plastograph as a consequence of extensive thermal oxidation. A quantitative correlation is found between the rate of change of the ultimate tensile strength of polystyrene and the extent of thermal oxidation. It is also demonstrated that a phenolic antioxidant, although it efficiently inhibits the thermal oxidation, has no specific effect on the photo-oxidation of polystyrene. A hindered amine light stabiliser, however, exhibits a pronounced photo-protective effect. A mixture of these additives combines the benefits of both.
Photo-chemical reactions in commercial poly(oxymethylene)
Polymer Degradation and Stability, 1979
Poly(oxymethylene) has been examined using infra-red, ultrariolet absorption and luminescence techniques. The first technique indicates that aldehydic carbonyl groups are present in the polymer whereas the latter two indicate the presence of ~,13unsaturated carbonyl groups. The behat'iour of these impurity carbonyl species during irradiation under sunlight-simulated conditions has also been examined. Possible mechanisms for the participation of these chromophoric units in the photooxidation of the polymer are discussed.
Recent advances in the photo-oxidation of polymers
Pure and Applied Chemistry, 1979
Recent results, mainly selected from the authors work on polystyrene, clearly indicate that a sound understanding of the photo-oxidation of polymers cannot be gained without quantum yields determination. These show that transfer of energy has a major role in the initiation of the photo-oxidation because of the high local concentration of reactive groups in polymers. It is also possible to find correlations between the rate of ageing of industrial polymers and the extent of chemical transformation of the materials prior to the exposure to ultraviolet light.
The Photo-Oxidation of Polymers. A Comparison with Low Molecular Weight Compounds
Elsevier eBooks, 1979
The photo-oxidation of polymers involves different steps in which their reactivity is different from that of low molecular weight conpounds. This is mainly due to the close vicinity of reactive groups in polymers and to the rigidity of the matrix. As a consequence, transfer of energy has a major role in the initiation of the photo-oxidation of most polymers on exposure to sunlight. It results in the sensitized decomposition of neighbouring hydroperoxide groups which, however, produce free radicals and thus initiate the oxidation less efficiently than model compounds in fluid solution. Scission of the polymer backbone, responsible for the alteration of the physical and mechanical properties, involves the decomposition of isolated hydroperoxide groups by two different mechanisms the relative importance of which changes with temperature.
Polymer Degradation and Stability, 2013
The behaviour of polyethylene with different contents in vinyl and t-vinylene groups have been studied by photooxidation with λ>300 nm light or by thermooxidation at a temperature of 100 °C. The oxidation was studied by infrared spectroscopy and it was shown that the same oxidation products were obtained, but with different relative concentrations depending on the conditions of ageing, i.e. photochemical or thermal conditions. The mechanisms by which the oxidation products are formed were recalled. The differences between photo-and thermooxidation were evidenced on the basis of the stability of ketones that do not accumulate in photochemical conditions, as a result of Norrish reactions. The influence of the initial amount of unsaturated groups on the rates of oxidation was characterized. It was shown that the concentration of unsaturations had no effect on the rate of photooxidation but dramatically influenced the stability in thermooxidative conditions.
Photo-oxidation of polymers—III
European Polymer Journal, 1978
Changes of molecular weight distribution resulting from vacuum photolysis and photo-oxidation of polystyrene have been determined by gel permeation chromatography. On irradiation at 253.7 nm, crosslinking is predominant in vacuo; in the presence of oxygen, crosslinking and main chain scission occur simultaneously because of light absorption by two or more different chromophores. Main chain scission is more important than crosslinking in the photolysis and photo-oxidation of polystyrene containing cumene hydroperoxide irradiated at 313 nm or containing benzophenone irradiated in the range 320-420 nm. In this last case, main chain scission and crosslinking are both strongly inhibited if the sample contains napthalene which acts as quencher of the excited triplet state of benzophenone, Only moderate inhibition is observed in the presence of 2,6-di-t-butyl-4 methylphenol. R~um6-Les changements de distribution de masse mol6culaire r6sultant de la photolyse sous vide et de la photoxydation du polystyr/me ont 6t6 d6termin6s au moyen de la chromatographie par perm6ation de gel. Lors de rirradiation fi 253.7 nm la r6ticulation est pr6pond6rante sous vide. En pr6sence d'oxyg6ne, r6ticulation et ruptures de chalne principale se produisent simultan6ment suite fi rabsorption de la lumi&e par au moins deux chromophores diff6rents. Les ruptures de chaines principales l'emportent sur la r6ticulation lors de la photolyse et de la photoxydation du polystyrene soit contenant de l'hydroperoxyde de cum6ne et irradi6 ~ 313 nm soit contenant de la benzoph6none et irradi6 dans le domaine 320-420nm. Dans ce dernier cas, les ruptures de chalne et la r6ticulation sont fortement inhib~es si l'6chantillon contient du naphtal6ne qui d6sactive le triplet excit6 de la benzoph6none; une inhibition mod6r6e est observ6e en presence de 2,6-di-t-butyl-4 m6thylph6nol.
Photooxidation of blends of polystyrene and poly(vinyl methyl ether): FTIR and AFM studies
Polymer, 2000
The chemical evolution of blends of poly(vinyl methyl ether) and polystyrene in conditions of photooxidation has been studied by infrared spectrometry and the photoproducts formed have been identified. The characterisation of the oxidation kinetics has permitted the detection of interactions between the two polymers. Analysis of the photooxidised samples by AFM has shown that the changes of the surface aspect could be characterised as a function of the irradiation time using several parameters and a tentative correlation between the modifications of the surface and the phase separation with the evolution of the chemical structure is proposed. ᭧