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991.
Dan Donescu Mihai Cosmin Corobea Violeta Uricanu Constantin Radovici Sever Serban Sorina Alexandra Garea 《Journal of Dispersion Science and Technology》2013,34(5):671-679
The emulsion polymerisation of vinyl acetate (VAc) in presence of sodium dodecylsulphate (SDS) and sodium montmorillonite (NaMMT) is used in order to achieve polymer‐clay hybrids. The influence of the polyvinylacetate (PVAc), SDS, and PVAc‐SDS complex on the NaMMT structure also was investigated. The VAc emulsion polymerization rate exhibits a maximum as the NaMMT concentration increases. The XRD patterns correspond to hybrids with intercalated structure. If a water soluble comonomer, ammonium sulphato ethylmethacrylate (ASEMA) is used for copolymerization with VAc, a exfoliated hybrid structure (from XRD spectra) is obtained. The solid materials were analysed by TGA, FTIR, XRD, SEM, and TEM. 相似文献
992.
以四氯化钛为钛源,针铁矿(α-FeOOH)为载体,采用水解沉淀法制备了金红石相二氧化钛(Ti2O)与α-FeOOH的复合光催化材料,并采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线能量散射谱和X射线光电子能谱对样品进行了表征.结果表明,低温下,金红石相Ti2O包覆于α-FeOOH表面,并形成复合结构;较高温下,铁离子进入金红石相Ti2O晶格,并形成铁掺杂金红石相Ti2O纳米管;中温下,样品兼有复合和掺杂两者特征.在室温下以甲基橙为降解对象,采用钨灯+氘灯(波长200~800nm)为光源,对样品的光催化活性进行了测试.结果表明,样品对甲基橙的光催化降解效果良好;与纯α-FeOOH和金红石相Ti2O相比,不同结构样品的光催化活性均有所提高,其中,复合兼掺杂型样品的光催化活性最高.由此可见,与α-FeOOH复合和铁掺杂是提高Ti2O光催化活性的有效途径. 相似文献
993.
Cristina Nerín Elena Canellas Joaquín Romero Ángel Rodriguez 《International journal of environmental analytical chemistry》2013,93(12):863-874
An analytical strategy has been proposed and optimized to study the permeability of several flexible plastic materials, some of them with high-barrier properties, versus naphthalene, methyl bromide, toluene, ethylbenzene, and ortho- and para-xylenes. The strategy involves using a system of concentric plastic bags made from the materials to be tested polyethylene (PE) and used as permeable plastics to facilitate the homogeneous distribution of a solid compound, such as naphthalene, in vapour phase. After the permeation test, the vapour phase containing the pollutants that cross the plastic barrier is trapped in a 12% ethanol–water solution and further analysed by SPME in headspace mode. Several experimental conditions as well as different samples were tested. The results obtained are shown and discussed. 相似文献
994.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1295-1303
ABSTRACT Stabilized nitroxide radicals (TEMPO and its 4-hydroxy- and 4-oxo-derivatives) have been examined as inhibitors of the radical polymerization at 60°C of methyl methacrylate using azobisisobutyronitrile as initiator. Inhibition periods have been recorded and also the rates of the subsequent polymerizations and the molecular weights of the resulting polymers. It is concluded that alkoxyamines, formed during the inhibition, affect the polymerizations and lead to lowering of the molecular weights of the resulting polymers. The effect is attributed to a radical-displacement process involving the alkoxyamine and a growing polymer radical. 相似文献
995.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):791-809
Abstract 4‐(3′,4′‐Dimethoxycinnamoyl)phenyl acrylate (DMCPA) containing pendant chalcone moiety was copolymerized with methyl methacrylate (MMA) by radical polymerization in ethyl methyl ketone at 70°C under a nitrogen atmosphere using benzoyl peroxide (BPO) as a free radical initiator. The prepared polymer was characterized by UV, FT‐IR, 1H‐NMR, and 13C‐NMR spectra. The composition of the copolymer was determined using 1H‐NMR analysis. The monomer reactivity ratios of copolymerization were determined using conventional linearization methods such as Fineman–Ross (r 1 = 0.26 and r 2 = 0.61), Kelen–Tudos (r 1 = 0.26 and r 2 = 0.61), and Ext. Kelen–Tudos (r 1 = 0.23 and r 2 = 0.59), and a non‐linear error‐in‐variables model (EVM) method using the computer program RREVM (r 1 = 0.2541 and r 2 = 0.6094). The molecular weights (M w and M n) of the copolymers were determined by gel permeation chromatography. Thermogravimetric analysis of the polymers in air reveals that the stability of the copolymers decreases with an increase in the mole fraction of MMA in the copolymers. The solubility of the polymers was tested in various polar and non‐polar solvents. The glass transition temperature of the copolymers was determined as a function of copolymer composition. The copolymers were sensitive to UV light and became crosslinked after irradiation with 254 nm light. 相似文献
996.
Gregory B. Kharas Emi Hanawa Jamie Lachenberg Beata Brozek Patricia Miramon Audris C. Mojica 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):420-424
Electrophilic trisubstituted ethylene monomers, some ring‐substituted 2‐phenyl‐1,1‐dicyanoethylenes, RC6H4CH?C(CN)2 (where R is 3‐Br, 4‐CH3O; 5‐Br, 2‐CH3O; 4‐Cl, 3‐NO2; 5‐Cl, 2‐NO2; 2‐CN, 3‐CN, 4‐CN, and 4‐(CH3)2N), were synthesized by piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, 1H‐ and 13C‐NMR. Novel copolymers of the ethylenes and vinyl acetate were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C‐NMR, GPC, DSC, and TGA. High T g of the copolymers, in comparison with that of polyvinyl acetate, indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 190–800°C range. 相似文献
997.
The thermal degradation of polytetrafluoroethylene oxide has been examined by the isothermal and thermogravimetric methods in the temperature range 450 to 650°C. The main components of the volatile gas are trifluoro-acetyl fluoride, carbonyl fluoride, and tetrafluoroethylene. The thermogravimetric decompositions of polytetrafluoroethylene oxide and of polytetrafluoroethylene have been compared. 相似文献
998.
Abstract Copolymers of 3-methoxy-4-acryloyloxybenzal phenylimine and methyl methacrylate with different feed ratios are synthesized in ethyl methyl ketone using benzoyl peroxide as a free radical initiator at 70 ± 1°CC. The polymers were characterized by IR and 1H-NMR spectroscopic techniques. Copolymer compositions were determined by lH-NMR analysis of the polymers. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman-Rose and Kelen-Tüdös. The molecular weights Mn and Mw of the polymers and the poly-dispersity index were determined by gel permeation chroma-tography. The intrinsic viscosities and the thermal properties of the homo-and copolymers are also discussed. 相似文献
999.
Blend membranes comprising cellulose acetate and polysulfone (CA/PSf) were prepared through a solution casting method using a different concentration of polyvinylpyrrolidone (PVP) as the pore former. Fourier transform infrared spectroscopy (ATR-FTIR) was used to investigate structural properties of membranes. Membranes morphology and its thermal properties were characterized by scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The strength of membranes was studied by mechanical stability. The effect of PVP concentration on separation performance of the prepared membranes was studied. The separation performance of prepared membranes was tested by using an aqueous solution of cadmium metal complexed with humic acid. The results showed that an increase in the PVP concentration in the cast film from 0 to 3 wt% increased the thermal stability, water content (%), pure water flux, and solute rejection. SEM results showed that the pore size decreased but the number of pores increased on an increase in the PVP concentration. 相似文献
1000.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1487-1505
The polymerization of methyl methacrylate initiated by the titanium(III)-salicylaldoxime redox system was studied in an aqueous sulfuric acid-ethanol medium in the temperature range of 20–30°C. The rates of polymerization were investigated at various concentrations of reductant, oxidant, ethanol, sulfuric acid, and monomer. Cyclic voltammetric sensing of salicylaldoxime kinetic conditions demonstrated its reduction behavior. From the results obtained, it was inferred that the polymerization reaction was initiated by an organic free radical arising from the titanium(III)-salicylaldoxime redox system and termination took place predominantly by mutual coupling and small fraction by chain transfer mechanism involving solvent molecules. The effects of some water-miscible organic solvents and surfactants on the rate of polymerization were investigated. The temperature dependence of the rate was studied and the activation parameters were computed using Arrhenius and Eyring plots. A suitable kinetic scheme has been proposed on the basis of experimental observations. 相似文献