Irradiation Effect on Photodegradation of Pure and Plasticized Poly (4-Methylstyrene) in Solid Films

The photodegradation of irradiated thin films of poly (para-methylstyrene) with 265 nm radiations in the presence of airand as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR Spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on stability of poly (para-methylstyrene) towards irradiations was also investigated. Blending with phthalate plasticizers was found to cause a higher efficiency of photodegradation than that obtained in doping with terephthalate plasticizers. The intensity of absorption was also found to increase with time of irradiation and in change in the shape of the spectra at longer wavelength, thus indicating a possibility of photodegradation of polymer chains. The analysis of the FT-IR spectra of the irradiated and non-irradiated samples, shows a predominant absorption associated with carbonyl compounds with 1740 cm-1. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, have provided an evidence for the photodegradation as well as photo-oxidation of polymeric chains. The presence of the plasticizer in the polymer backbone was found to accelerate the photodegradation of polymeric chains.

Kinetic Study of the Effect of Plasticization on Photodegradation of Polystyrene Solid Films

The effects of UV-irradiation on stability of pure and blended polystyrene films with phthalate and terephthalate plasticizers were studied in presence of air. UV-visible, fluorescence and FT-IR techniques were used to study the photodegradation of irradiated polystyrene films. Increase of irradiation times of polystyrene films caused an increase in the intensity of the main absorption band and the increase in the intensity of a new absorption band at longer wavelength, thus indicating a possibility of photo degradation of polystyrene chains. The influence of added plasticizers, dimethyl terephthalate, diethyl terephthalate, dioctyl terephthalate, dioctylphthalate, and dibutyl phthalate on photo-quenching of the polymer fluorescence band was also investigated, and found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of excimer and monomer fluorescence bands maxima was also found to decrease with a small red shift with the increase in irradiation times. These changes may be attributed to the formation of new photo-products resulted from the photodegradation of irradiated polymeric chains. The photo- quenching rate constant was found to increase with the increase of the molar mass and bulkiness of the used plasticizers and to increase with the increase in irradiation time. The rate constant of the photo quenching process was found to decrease with the increase in the percent of added plasticizers, indicating that the added plasticizers might act as UV-absorbers which inhibited the photodegradation process. The analysis of the FT-IR spectra of the irradiated and nonirradiated samples showed a noticeable formation of new broad band centered at 1727 cm-1, and its intensity was found to increase with the increase in irradiation time and also with the increase in the amount of added plasticizer. In addition, the observed increase in the intensities of the carbonyl and hydroxyl absorption regions of the FT-IR spectra provided evidence for the photodegradation as well as photo-oxidation of polymeric chains.

Plasticization Effect on the Photodegradation of Poly (4-Chlorostyrene) and Poly (4-Bromostyrene) Films

The photodegradation of thin films of poly (4-chlorostyrene) and poly (4-bromostyrene) with 265 nm radiation in the presence of oxygen and as a function of irradiation time has been studied mainly using fluorescence, FT-IR, and UV-VIS spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on photo-oxidative degradation was also investigated. Phthalate and terephthalate-plasticizers were found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of absorption was also found to increase with irradiation time and in the intensity of a new absorption band at longer wavelength. The appearance of new fluorescence bands in the irradiated polymer films can well indicate a possibility of photodegradation of polymer films. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, providing evidence for the photodegradation as well as the photo-oxidation of polymeric chains. The increase in the analyzed ranges was attributed to the formation of alcohols, aliphatic ketones and to the increase in the number of (C=C) that resulted from hydrogen abstraction during chains - scission.

Fabrication and photodegradation properties of TiO_2 nanotubes on porous Ti by anodization

Both Ti foil and porous Ti were anodized in 0.5%HF and in ethylene glycol electrolyte containing 0.5%NH4F(mass fraction) separately. The results show that TiO2 nanotubes can be formed on Ti foil by both processes, whereas TiO2 nanotubes can be formed on porous Ti only in the second process. The overhigh current density led to the failure of the formation nanotubes on porous Ti in 0.5%HF electrolyte. TiO2 nanotubes were characterized by SEM and XRD. TiO2 nanotubes on porous Ti were thinner than those on Ti foil. Anatase was formed when TiO2 nanotubes were annealed at 400 °C and fully turned into rutile at 700 °C. To obtain good photodegradation, the optimal heat treatment temperature of TiO2 nanotubes was 450 °C. The porosity of the substrates influenced photodegradation properties. TiO2 nanotubes on porous Ti with 60% porosity had the best photodegradation.

One-pot synthesis of ordered mesoporous Cu-KIT-6 and its improved catalytic behavior for the epoxidation of styrene:Effects of the pH value of the initial gel

The heterogeneously copper-catalyzed oxidative cleavage of styrene was studied using copper-doped mesoporous KIT-6（CU-KIT-6_x） prepared via pH adjustment（where x is the pH：1.43,2.27,3.78,3.97,4.24 or 6.62）.Variations in the catalyst structure and morphology with pH values were characterized by X-ray power diffraction,nitrogen adsorption-desorption analysis,transmission electron microscopy and X-ray photoelectron spectroscopy.As the pH value applied during the initial synthesis,the resulting Cu-KIT-6_x exhibited different structural,textural and surface characteristics,especially in terms of specific copper species and copper content At a pH value of 3.78,approximately 4.6 wt%copper（Ⅱ） was successfully incorporated into the framework of the initial KIT-6,in the form of-Cu-O-Si- groups.The catalytic performance of each catalyst was evaluated by following the epoxidation of styrene,employing tert-butyl hydroperoxide as the oxidant and CH_3CN as the solvent.A significant styrene conversion of 43.5%with 86.6%selectivity for the desired styrene epoxide was obtained over the Cu-KIT-63.78.A higher Cu content,an ordered cubic laid mesoporous architecture and various specific textural characteristics all combined to endow the Cu-KIT-63.78 with high catalytic activity and good stability.

An Investigation on the Polymerization of Styrene by Fluorescence Probe Technique

The polymerization of styrene is monitored by pyrene excimer formation. The ratio of monomer to excimer intensities ( I m/ I e) of pyrene increases as polymerization proceeds. The increase of I m/ I e is ascribed to the increase of microviscosity surrounding the probes forming excimer during polymerization. The linear relationship between the changing rate of I m/ I e and the polymerization rate of styrene is obtained. Therefore, I m/ I e may be used to monitor the progress of the polymerization of styrene.

Study on Structure and Performance of Starch and Styrene Graft Copolymer

[Objective] The paper was to study the structure and performance of starch and styrene graft copolymer. [Method] The microscopic structure of corn starch and styrene graft copolymer was analyzed by using infrared spectrum and scanning electron microscope, and the property of starch and styrene graft copoly- mer was confirmed through grinding experiment, tensile strength, water absorption rate, hot water resistance properties and enzymatic properties analysis. [Result] The starch and styrene graft copolymer had the properties of thermoplastic and microbial degradation. IConclusion] The starch and styrene graft copolymer is expected to be developed as a biodegradable material.

Characterization of V_2O_5/MoO_3 composite photocatalysts prepared via electrospinning and their photodegradation activity for dimethyl phthalate

Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity of the composites were evaluated by their ability to photodegrade methylene blue and dimethyl phthalate（DMP） under visible-light irradiation. Compared with pure V2O5 and MoO 3,the V2O5/MoO 3 composites showed enhanced visible-light photocatalytic activity because of a V 3d impurity energy level and the formation of heterostructures at the interface between V2O5 and MoO 3. The optimal molar ratio of V to Mo in the V2O5/MoO 3 composites was found to be around 1/2. Furthermore,high-performance liquid chromatographic monitoring revealed that phthalic acid was the main intermediate in the photocatalytic degradation process of DMP.

Photoreductive degradation of sulfur hexafluoride in the presence of styrene

Sulfur hexafluoride （SF6） is known as one of the most powerful greenhouse gases in the atmosphere. Reductive photodegradation of SF6 by styrene has been studied with the purpose of developing a novel remediation for sulfur hexafluoride pollution. Effects of reaction conditions on the destruction and removal efficiency （DRE） of SF6 are examined in this study. Both initial styrene-to-SF6 ratio and initial oxygen concentration exert a significant influence on DRE. SF6 removal efficiency reaches a maximum value at the initial styrene-to-SF6 ratio of 0.2. It is found that DRE increases with oxygen concentration over the range of 0 to 0.09 mol/m^3 and then decreases with increasing oxygen concentration. When water vapor is fed into the gas mixture, DRE is slightly enhanced over the whole studied time scale. The X-ray Photoelectron Spectroscopy （XPS） analysis, together with gas chromatography-mass spectrometry （GC-MS） and Fourier Transform Infrared spectroscopy （FT-IR） analysis, prove that nearly all the initial fluorine residing in the gas phase is in the form of SiF4, whereas, the initial sulfur is deposited in the form of elemental sulfur, after photodegradation. Free from toxic byproducts, photodegradation in the presence of styrene may serve as a promising technique for SF6 abatement.

Mechanism study on UV-induced photodegradation of nonylphenol ethoxylates by intermediate products analysis

Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate products including aldehydic compounds, carboxylic compounds and cyclohexanyl compounds were identified. Five main degradation routes involving the oxidation of the alkyl chain and ethoxylate unit, shortening of the alkyl chain and ethoxylate unit, hydrogenation of the benzene ring were proposed.

Synthesis of Ln-doped MCM-41 mesoporous materials and their catalytic performance in oxidation of styrene

Using cetyl-trimethyl-ammonium bromide （CTMAB） as the template agent and tetraethylorthosilicate （TEOS） as the silica source, the MCM-41 mesoporous materials were synthesized with La or Ce incorporated in the framework under hydrothermal conditions. The structure and the state of La or Ce were investigated through the analyses of XRD, nitrogen adsorption-desorption, FT-IR, and UV-Vis. XRD and N2 adsorption-desorption results showed that Ln-MCM-41 exhibited the loss of the lattice ordering of the MCM-41 construct, and larger unit cell parameter and pore diameter than pure silica MCM-41. The FT-IR and UV-Vis results indicated the presence of isolated tetra-coordinated La or Ce ions in the framework and other Ln species dispersed highly on the Ln-MCM-41 surface simultaneously. Furthermore, their catalytic behaviors in the oxidation of styrene were studied using H2O2 as the oxidant. The La-MCM-41 catalysts exhibited high reactivity and the reactivity increased with the increase of the La content in the La-MCM-41 samples. On the contrary, Ce-MCM-41 catalysts showed low reactivity in the oxidation of styrene and the conversion of styrene decreased with the increase of the Ce content in the Ce-MCM-41 samples.

Leaching of styrene and other aromatic compounds in drinking water from PS bottles

Bottled water may not be safer, or healthier, than tap water. The present studies have proved that styrene and some other aromatic compounds leach continuously from polystyrene （PS） bottles used locally for packaging. Water sapmles in contact with PS were extracted by a preconcentration technique called as ＂purge and trap＂ and analysed by gas chromatograph-mass spectrometer （GC/MS）. Eleven aromatic compounds were identified in these studies. Maximum concentration of styrene in PS bottles was 29.5 μg/L. Apart from styrene, ethyl benzene, toluene and benzene were also quantified but their concentrations were much less than WHO guide line values. All other compounds were in traces. Quality of plastic and storage time were the major factor in leaching of styrene. Concentration of styrene was increased to 69.53 μg/L after one-year storage. In Styrofoam and PS cups studies, hot water was found to be contaminated with styrene and other aromatic compounds. It was observed that temperature played a major role in the leaching of styrene monomer from Styrofoam cups. Paper cups were found to be safe for hot drinks.

Photodegradation of acetochlor in water and UV photoproducts identified by mass spectrometry

The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous solution was rapidly degraded. The half-lives were 7.1, 10.1, and 11.5 min in de-ionized water, river water and paddy water, respectively. Photoproducts of acetochlor were identified by gas chromatography/mass spectrometry(GC/MS) and found at least twelve photoproducts resulted from dechlorination with subsequent hydroxylation and cyclization processes. The chemical structures of ten photoproducts were presumed on the basis of mass spectrum interpretation and literature data. Photoproducts are identified as 2-ethyl-6-methylaniline; N,N-diethylaniline; 4,8-dimethyl-2-oxo-1,2,3,4- tetrahydroquino-line; 2-oxo-N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)acetamide; N-(ethoxymethyl)-2′-ethyl-6′-methylformanilide;1-hydroxyacetyl-2-ethoxyl-7-ethylind ole; 8-ethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 4,8-dimethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 2-hydroxy-2′-ethyl-6′-methyl-N-(ethoxymethyl)acetanilide and a compound related to acetochlor. The other two photoproducts were detected by GC/MS although their chemical structure was unknown.

Studies on the Mechanism of the Direct Synthesis of Styrene form Benzene and Ethylene

The adsorption behavior and description behavior of benzene , ethylene and ethylbenzene over HZSM-5 and Co/HZSM-5 catalysts were studied by means of TPSR (Temperature programmed surface reaction) technique. TPSR results of ben- zene and ethylene co-adsorption show that the maian products are styrene , ethylben- zene, toluene, propane, and butane. In a separate experiment of ethylbenzene ad- sorption, styrene . toluene and benzene are formed due to cracking and dehydro- genation. The mechanism of styrene formation was proposed , i. e. , the reaction was carried out via. the dehydrogenation of mediate species ethylbenzene according to the results of TPSR-MS , activity testing and thermodynamic analysis.

MONOMER REACTIVITY RATIO AND THERMAL PERFORMANCE OFα-METHYL STYRENE AND GLYCIDYL METHACRYLATE COPOLYMERS

Synthesis and characterization of the copolymers （PAG） of α-methyl styrene （AMS） and glycidyl methacrylate （GMA） are presented. The copolymers of PAG were characterized by gel permeation chromatography （GPC）, Fourier transform infrared spectroscopy （FTIR）, nuclear magnetic resonance （^1H-NMR） and thermogravimetery （TG）. Based on the copolymer compositions determined by ^1H-NMR, the reactivity ratios of AMS and GMA were found to be 0.105 ± 0.012 and 0.883 ± 0.046 respectively by Kelen-Tudos method. TG revealed that thermal stability of the copolymers decreased with increasing the AMS content in the copolymers, which indicated that the degradation was mainly caused by the chain scission of AMS-containing structures. Under heating, the copolymers depolymerize at their weak bonds and form chain radicals, which could further initiate other chemical reactions.

CATALYTIC COPOLYMERIZATION OF STYRENE AND ETHYLENE BY NEUTRAL NICKEL(Ⅱ) COMPLEXES IN EMULSION

Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were characterized by an array of techniques including NMR,GPC,TEM,WAXD and DSC.The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units,and their M_W is in the range of 10~5-10~6.By enhancing the electron withdrawing of the s...

Copolymerization of Styrene with N-phenylmaleimide by Rare Earth Coordination Catalysts

Copolymerization of styrene (St) with N-phenylmaleimide (NPMI) was studied with rare earth coordination catalyst Nd(naph)3-AlEt3 in toluene. Characterization of the copolymers showed that the copolymers possess an alternating structure.

Enhanced photodegradation of phenolic compounds by adding TiO_2 to soil in a rotary reactor

Photodegradation ofpentachlorophenol （PCP） and p-nitrophenol （PNP） in soil was carried out in a designed rotary reactor, which can provide the soil particles with continually uniform irradiation, and on a series of thin soil layers. TiO2, as a kind of environmental friendly photocatalyst, was introduced to the soil to enhance the processes. Compared with that on the soil layers, photodegradation of PCP at initial concentration of 60 mg/kg was improved dramatically in the rotary reactor no matter whether TiO2 was added, with an increase of 3.0 times in the apparent first-order rate constants. The addition of 1 wt% TiO2 furthered the improvement by 1.4 times. Without addition of TiO2, PNP （initial concentration of 60 mg/kg） photodegradation rate in the rotary reactor was similar to that on the soil layers. When 1 wt% additional TiO2 was added, PNP photodegradation was enhanced obviously, and the enhancement in the rotary reactor was 2 times of that on the soil layers, which may be attributed to the higher frequency of the contact between PNP on soil particles and the photocatalyst. The effect of soil pH and initial concentrations of the target compounds on the photodegradation in the rotary reactor was investigated. The order of the degradation rate at different soil pH was relative to the aggregation of soil particles during mixing in the rotary reactor. Photodegradation of PCP and PNP at different initial concentrations showed that addition of TiO2 to enhance the photodegradation was more suitable for contaminated soil with higher concentration of PCP, while was effective for contaminated soil at each PNP concentration tested in our study.

Visible Light Induced Photodegradation and Phototoxicity of Phloxine B and Uranine

Ohjective To determine the visible light-induced photodegradation kinetics of two xanthene photosensitizers, phloxine B and uranine, in solution and on the surface of silica TLC plates, and to examine the phototoxicity of residues of degradation, which could provide valuable safety data on the two photosensitizers and other xanthene chemicals when applied in the environment. Methods UV-Vis absorption during photodegradation was monitored with a Unico 2102 spectrophotometer. Organic content of samples was measured with a Shimadzu TOC 4100. Phototoxicity tests were carried out using Saccharomyces cerevisiae with the methods modified from Daniels. Results When phloxine B and uraniue degraded in solution, their apparent rate constant k was 0.0019 and 0.0027 min^-1, respectively. The total organic carbon （TOC） content decreased by approximately 50% during the 8 h irradiation period, which led to a gradual decrease in phototoxicity of the residues. The photodegradation of photosensitizers on the surface of silica TLC plates was much faster than that in the solution. The apparent rate constant k and the half life of phloxine B were 0.0073 min^-1 and 95 min, respectively. Conclusion Visible light can rapidly induce photodegradation of phloxine B and uranine. The phototoxicity of residues is also decreased. The environmental risk of applications of phloxine B and uranine is minimal.

Morphology and crystal-plane effects of Zr-doped CeO2 nanocrystals on the epoxidation of styrene with tert-butylhydroperoxide as the oxidant

The morphology effect of Zr-doped CeOwas studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zrdoped CeOnanorods exhibited the highest catalytic performance（yield of styrene oxide and TOF value）followed by nanoparticles and nanocubes. For the Zr-doped CeOnanorods, the apparent activation energy is 56.3 k J/mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes（73.3 and 93.4 k J/mol）. The high resolution transmission electron microscopy results indicated that（100） and（110） crystal planes are predominantly exposed for Zr-doped CeOnanorods while（100）and（111） for nanocubes,（111） for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeOnanorods is mainly attributed to the higher percentage of Cespecies and more oxygen vacancies, which are associated with their exposed（100） and（110） crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeOnanorods did not lose its initial high catalytic activity after five successive recycles.