Photochemical behaviour of poly(vinylmethylether) (original) (raw)
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Photo-oxidation of poly(vinylbutyral)
Polymer Photochemistry, 1981
The photo-oxidation o[ poly(vinylbutyral) (PVB) induced by a Xenon arc light has been examined using IR, NMR and UV spectroscopy. The tensile strength and melt index o[ samples being photo-oxidised were also [ollowed. PVB degrades readily when exposed to light fi, om a Xenon arc. The process o[ photo-oxidation is autocatalytic, the key role being played by ketones and hydroperoxide intermediates. Ring-opening and main chain scission accompanied by an increase in carbonyl group and double bond contents are the principal reactions taking place. The spectral sensitivity of PVB towards 326, 369 and 445 nm light was found to be 60, 8 and 1, respectively. This effect may only partially be offset by covering the material with glass.
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. ᭧
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.
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.
Photooxidative degradation of polyether-based polymers
Macromolecular Symposia, 1999
The mechanisms of photooxidation of several polyether based polymers were compared in order to give general rules of orientation of the oxidative reactions. These polymers were a poly(ether-ester) and two poly(etherurethane)s. The behavior of the polyether component as homopolymer was also studied. This study was extended to copolymers of fluorinated olefins and ally1 or vinyl ethers, and the non fluorinated homologues. The elucidation of the photooxidation mechanisms was based on the identification of the photoproducts by analysis of both the solid polymeric matrix and the gaz phase formed on irradiation. It was shown that the photochemical sensitivity of the polyether component was responsible for the rapid oxidation of the copolymers. However, in the case of the fluorinated compounds, different behaviors were observed. It was shown that the presence of the fluorine atoms strongly influenced the orientation of the reaction and modified the oxidation kinetics. The reactivity of the methylene groups in a-position of the oxygen atom of the ether groups were not found to be equivalent regarding oxidation and the secondary was more oxidizable than the tertiary one.
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.
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.
Polystyrene photooxidation. 2. A pseudo wavelength effect
Macromolecules, 1992
The photoproducts formed in polystyrene photooxidized by exposure to long wavelengths (A L 300 nm) or short wavelength (A = 253.7 nm) absorbing in the IR range were identified and reported in the preceding paper. It was shown that, despite some differences in the distribution of oxidation photoproducts, the same products were obtained. The present paper report8 on complementary experiments carried out at a different temperature and on microspectrophotometric determination of the photoproduct profiles. The apparent differences resulting from the short-or long-wavelength irradiation are attributed to the diffusion of the low molecular weight photoproducts. A general mechanism accounting for the photooxidation of the polystyrene at short or long wavelengths is given.
Comparison of Photooxidation and Thermal Oxidation Processes in Poly(ether imide)
Macromolecules, 2005
Thermal oxidation and photooxidation processes occurring in poly 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride-1,3-phenylendiamine copolymer (ULTEM), were investigated and compared. The study aimed at finding possible differences in the oxidation pathways of this complex polymer by using the analytical power of MALDI techniques. ULTEM films were subjected to photooxidation by exposure at 60°C in a UV accelerated chamber (Q-UV Panel) in atmospheric air, and the oxidative process was followed as a function of the exposure time. Relevant structural information on the photooxidized ULTEM species was extracted from the MALDI spectra. These data show the presence of polymer chains containing acetophenone, phenyl acetic acid, phenols, benzoic acid, phthalic anhydride, and phthalic acid end groups. The mechanisms accounting for the formation of photooxidation products of Ultem involve several reactions: (i) photocleavage of methyl groups of the N-methyl phthalimide terminal units; (ii) photooxidative degradation of the isopropylidene bridge of BPA units; (iii) photooxidation of phthalimide units to phthalic anhydride and phthalic acid end groups. Some of these cleavage pathways are specific for the photooxidation process and the oligomers deriving from them are absent in the thermal by oxidized Ultem samples, whereas the thermal cleavage of the diphenyl ether units appears to occur only in the thermal oxidation process.
Physics Procedia, 2014
Disturbances of the photochemical evolution involved in the photolysis and in the photo-oxidation at long wavelengths (λ≥300 nm) of poly(propylene glycol-maleatophtalate cross-linked by the styrene (UP), caused by the addition of photo-active pigment such as zinc sulfide or black iron oxides, and no photoactive inorganic fillers such as calcium carbonate have been analyzed by means of FTIR and U.V. spectrophotometry. The photo-oxidation observed by FTIR of the polymer UP in the presence of inorganic fillers leads to the same photoproducts such as ones of the photo-oxidation of the virgin polymer, but the oxidation rate is greatly affected by the nature and the percentage of the inorganic filler. Zinc sulfide and black iron are incorporated in the film of polymers, The absorption spectra of ZnS reveals that this pigment is not as absorbent as titanium oxide in a more limited field. On the other hand, with a very low inner filter effect, black iron oxides promote the formation of absorbing photoproducts. The addition of Calcium carbonate non-absorbing filler to the UP, causes a slight decrease in the evolution of the I.