Photo-oxidation stabilization of polystyrene by aromatic ultraviolet light absorbers forming charge transfer complexes (original) (raw)
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Photodegradation of Polystyrene Films Containing UV-Visible Sensitizers
Journal of Research Updates in Polymer Science, 2013
The photodegradation of polystyrene films has been investigated in the presence of sensitizers such as benzophenone (BP) and thioxanthone (TX). The phototransformations were studied by infrared and UV-Vis spectroscopy. The results indicate that these photosensitizers accelerate and increase the efficiency of the photodegradation and the photo-oxidation processes in polystyrene and increase the formation of double bonds in the polymer. In all these process, TX showed a larger photosensitization efficiency than BP. Flash photolysis experiments indicate that the triplet reactivity of both sensitizers towards polystyrene are similar, so that the higher efficiency of thioxanthone when compared with benzophenone should be assigned to its larger absorptivity, as well as to the absorptivity of its degradation products in the irradiating region.
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.
Study of The Photostbilization Of Polystyrene In The Presence And Absence Of Schiff Base Derivatives
2022
Abatract The initiated photodegradation of polystyrene films notice able all around were examined (for 400 hrs.) in the being and absence of Schiff bases for benzoxazin product compounds by quickened weathering analyzer. The adding of (0.1% wt/v) of organic compounds to polystyrene films (thickness, 25μm) diminished the degradation of the polystyrene. The rate of degradation was trailed by an expansion in absorbtion of carbonyl for polymers utilizing viscosity, I.R., and UV spectra estimation. As per the results, the initiated degradation instruments of polystyrene films were recommended under the exploratory term utilized utilizing temperature 45 oC, radiation of UV at λ = 313 nm , illumination force 3.49x10-5 einsteins.dm-3.S-1.
Photostabilization of Polystyrene Films by Chromium complex
Journal of Garmian University, 2018
The photo sensitized degradation of polymer system is occasionally used as a means of solving the problem of environmental pollution, photostabilization of polystyrene films using chrom complexes was investigated. Poly styrene films with a thickness of 80μm and contains complexes concentration of 0.05% wt were produced by the casting method with chloroform being the solvent The photostabilization activities of these complexes were determined by monitoring changes in carbonyl,(I CO) and hydroxyl,(I OH) indices and calculating the photodecomposition rate constant (k d), the average molecular weight for the studied films The results obtained showed that the photostabilization activity of polystyrene film in the presence of the complexes as additive follows the trends:
On the photolysis of chain-chlorinated polystyrene
Journal of Photochemistry and Photobiology A: Chemistry, 1995
Copolymers of styrene and a-chlorostyrene containing 19%-95% a-chlorostyrene, prepared by photochlorination of polystyrene (PSt), were irradiated with UV light at hint = 254 nm (continuous irradiation) or at Ainc = 266 nm (flash photolysis). The major photochemical reactions occurring in films of highly chlorinated polymer (CPSt-95, TC1=0.95 El atoms per repeating unit) are chlorine release ~b(HC1) = 2 X 10-2) and the accompanying formation of carbon-carbon double bonds. Main-chain scission is a minor process of quantum yield ~b(S) = 2 × 10-3, but brings about a decrease in the average molar mass of CPSt-95. Flash photolysis studies revealed the existence of ~inglet excimers (~'~< 20 ns), triplets (z-65 ns) and benzyl-type radicals (z>~ 5 ms). The quantum yields of chlorine release and formation :)f benzyl-type radicals, measured in tetrahydrofuran solution, are of equal magnitude (about 0.2). By contrast, photochemical reactions in :opolymers of low chlorine content resemble those induced in polystyrene, e.g. at 3'cl =0.19 intermolecular cross-linking dominates over main-chain cleavage and renders the polymer insoluble.
Photodegradation kinetics of poly(para-substituted styrene) in solution
Polymer Degradation and Stability, 2008
The UV irradiation effects on stability of polystyrene, poly(4-methoxystyrene), poly(4-methylstyrene), poly(a-methylstyrene), poly(4-tert-butylstyrene), poly(4-chlorostyrene), and poly(4-bromostyrene) in dichloromethane, dichloromethane, tetrahydrofuran, and N,N-dimethylformamide solutions were studied in the presence of oxygen at different intervals of irradiation time. The photodegradation was studied at 293 K using fluorescence spectroscopy. Solutions of these polymers were accompanied by quenching of monomer and excimer emissions during the exposure of their solutions to UV light, and by a change in the structure of the fluorescence spectrum. Irradiation of poly(4-methylstyrene) and poly(amethylstyrene) at excitation wavelength of 265 nm showed an increase of fluorescence intensity of a broad band, at longer wavelength without clear maxima. This may indicate that photodestruction of these polymers by irradiation with light of frequency absorbed by the polymer, may start from a random chain scission, with the possibility of formation of polyene and carbonyl compounds.
Study the Photo-degradation of poly styrene –co-butadiene in presence of Ni complex and TiO2
2020
Abstract. In this work, the induced photo-degradation of poly styrene –co-butadiene films in the air has been studied (for 400 hr.) in the presence and absence of TiO2 dye and Ni complex, benzyl bis(benzoylhydrazone) Ni, as a photosensitizer by accelerated weathering tester, which are accomplished with the use of the Ultraviolet radiation at λ = 313nm, intensity of light of 3.490*10-5 Einstein/dm3.S at 45oCtemperature. The rate of the photo-degradation has been followed with an increase in the polymers, hydroxyl and carbonyl absorbance of the use of the UV-visible and infrared (IR) spectra respectively and viscometer measurement. The addition of (0.1 wt %) of TiO2 dye and Ni complex to poly styrene –co-butadiene films (25μm thick) improved the photo-degradation of polymer films, , and the photo-degradation with Ni complex higher than the photo-degradation of polymer with TiO2 dye where the degradation constant for Ni complex in polymer is higher than TiO2 dye.
Kinetic studies of the photo-degradation of poly(arylene vinylenes)
Journal of Luminescence, 2012
The kinetics of the degradation of a homologous series of Poly phenylene vinylenes in which the phenylene units of the PPV structure are systematically substituted by naphthyl and anthyrl units is presented. Degradation is monitored according to the decay of the long wavelength absorption maximum upon illumination with UV radiation. Compared to Toluene solution, the photo-degradation is seen to be accelerated in Chloroform solution. All decays are fitted with first order kinetics. It is found that all substitutions improve the stability of the vinylene polymers against decay. In particular the highly electro-negative naphthyl group serves to drastically increase the stability due to electron depletion across the vinyl bond. The decay rate is shown to correlate well with the variation of the electronic properties of the backbone and with the reduction of vinylene bond strength as measured using Raman spectroscopy.
The photostabilization of polystyrene (PS) films by 2,3-dihydro-(5-mercapto-1,3,4-oxadiazol-2-yl)-phenyl-2-(substituted)-1,3,4-oxazepine-4,7-dione compounds was investigated. PS films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform as a solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PS with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ cs ) of these complexes in PS films was evaluated and found to range between 3.31 × 10 -6 and 7.89 × 10 -6 . Results obtained showed that the rate of photostabilization of PS in the presence of the additive follows the trend (I > II > III > IV). According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive like UV absorption, peroxide decomposer and radical scavenger.
Polymer Degradation and Stability, 1982
Processing oJ'a styrene-acrylonitrile copolymer (SA N) at 160 °C in the presence of air results in the thermal oxidation of the styrene units and in the partial cyclisation of sequences of acrylonitrile units. Acetophenone groups and chain scissions are produced in equal number. As a consequence, the ultimate tensile strength is reduced and subsequent photo-oxidation can be initiated more efficiently. The rate of change of the ultimate tensile strength on exposure to ultraviolet light is proportional to the extent of previous thermal oxidation. A quantitative correlation is found between the ultimate tensile strength and the concentration of aeetophenone groups produced by thermal oxidation, photo-oxidation, or a combination of both. A phenolic antioxidant has been shown to have a detrimental effect on the tensile strength during processing. Moreover, when mixed with a hindered amine light stabiliser, it practically annihilates the photo-protective effect of the latter.