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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Raw, dewaxed and oxidized jute fibres and those chemically modified with phenol and formaldehyde (treatment done for 3 h at 95° C and pH 8) before or subsequent to oxidation, were subjected to graft copolymerization with methyl methacrylate (MMA) in the presence or absence of some other monomers such as maleic anhydride (MA) or methacrylic acid (MAA) in limited aqueous system using K2S2O8 as the initiator under photoconditions with the objective of inducing improved rot resistance and dyeability without loss in tensile strength of the fibre. For preparing oxy-jute, dewaxed and preswollen (dewaxed jute fibre swollen with 10% aqueous urea at 90° C for 2h) jute fibre were separately subjected to mild oxidation or bleaching using aqueous H2O2 and NalO4 and non-aqueous chlorine (Cl2 in CCl4) under specified conditions. Optimum conditions for graft copolymerization have been established by examination of the effect of such variables as monomer concentration, time of polymerization and nature of chemical modification of jute fibre prior to vinyl grafting. Percentage grafting, tenacity (g denier−1), dye fixation (%) and rot resistance (expressed as percentage retention of tensile strength of the fibre after a standard soil burial test) were evaluated and analysed. High rot resistance (80–90% retention of tensile strength after soil burial test) and dye fixation (%) of as high as 86% were readily obtained for grafted jute fibres. Washing fastness and light fastness properties of the dyed fibres (grafted and ungrafted) were also examined and compared.
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polymerisation einiger Vinylmonomerer wie z. B. Methylmethacrylat, Äthylmethacrylat, Methacrylsäure und Styrol wird in wäßriger Phase durch Bisulfit ausgelöst. Bei anderen Vinylverbindungen, wie. z. B. Acrylnitril, Vinylacetat, Methylacrylat und Acrylsäure tritt unter den gleichen Bedingungen Jedoch Keine Polymerisation ein.Der Mechanismus der Startreaktion wird diskutiert.In bezug auf die Bisulfit-Konzentration verläuft die Polymerisation des Methylmethacrylats nahezu nach der 0,5 ten Ordnung.Die quantitative Endgruppenbestimmung mittels einer kolorimetrischen Technik ergab einen Gehalt von etwa 2 Sulfonat-Endgruppen (-SO3H) pro Makromolekül. Sulfat-Endgruppen (-OSO3H) wurden nicht gefunden. Bei sehr geringen Initiatorkonzentrationen ( 〈 0,005 mol/l) wurden einige Hydroxylgruppen gefunden; jedoch ergab sich auch in diesen Fällen die Summe von Sulfonat- und Hydroxylendgruppen zu 2 pro Makromolekül.
    Notes: Bisulfite initiates aqueous polymerization of certain vinyl monomers such as methyl methacrylate, ethyl methacrylate, methacrylic acid and styrene but it fails in case of acrylonitrile, vinyl acetate, methylacrylate, and acrylic acid under identical conditions.The mechanism of initiation has been discussed.Catalyst exponent of this initiator with respect to methyl methacrylate is near about 0.5. Quantitative determination of endgroup by dye techniques of the polymers obtained show that about 2 sulfonate (-SO3H) endgroups are present per chain in almost all cases. No sulphate endgroup (-OSO3H) is ever found. In case of very low initiator concentration ( 〈 0.005 mole/1.), some hydroxyl endgroups are also found in general but the total (sulfonate and hydroxyl combined) amounts to about 2 per polymer chain.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Kupfer(I)chlorid und Kupferpulver löste in angesäertem Wasser die Polymerisation von Methacrylsäuremethylester, Methacrylsäureäthylester, Methacrylsäure und Styrol aus. Jedoch zeigte sich under identischen Bedingungen keine Polymerisation bei Acrylnitril, Acrylsäuremethylester und bei der Acrylsäure.Der Katalysatorexponent dieses Initiators hat in saurem, wäßrigem Medium beim Methacrylsäuremethylester den Wert 0,38.Die quantitative Endgruppenbestimmung in den erhaltenen Polymeren mittels der Farbtechniken ergab zwei Hydroxylendgruppen je Kette, wenn Säure und geringe Spuren Sauerstoff Vorhanden waren. Wurde jedoch der Sauerstoff sorgfälting ausgeschlossen, dann waren nur wenige Hydroxylendgruppen eingebaut.Es wurde der Mechanismus der unter verschiedenen experimentellen Bedingungen durchgefuhrten Startreaktion erörtert.
    Notes: Cuprous chloride and copper powder (in acid media) initiate the aqueous polymerization of certain vinyl monomers such as methyl methacrylate, ethyl methacrylate, methacrylic acid and styrene but it fails in case of acrylonitrile, methyl acrylate, and acrylic acid under identical conditions. Catalyst exponent of this initiator (in acid aqueous media) with respect to methyl methacrylate is 0.38.Quantitative determination of end-groups by dye techniques of the polymers obtained shows that about 2 hydroxyl end-groups per chain are present under acidic conditions in presence of slight traces of oxygen but in rigorous absence of oxygen, very little OH end-groups are found incorporated.The mechanism of initiation under different experimental condition is discussed.
    Additional Material: 4 Ill.
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It was found that the Py-SO2 complex (4-140 mmol·1-1) initiates the photopolymerization of methyl methacrylate (MMA) in bulk at 40°C, the initiator exponent, kp2/kt, and the monomer exponent being 0,30, 1,27·10-2 1·mol-1·s-1, and 1,00, respectively. The radical generation is followed by an in-situ initiator-monomer complexation reaction. The kinetics of the photopolymerization of MMA were also studied using the (Py-SO2)-complex (0,01-0,35 mol·1-1) in redox combination with benzoyl peroxide (BZ2O2) (2 - 110 mmol·1-1) as initiator in the presence of variable concentrations of pyridine (1 - 7 mol·1-1). The initiation depends on the concentrations of all the reactants in the system, and the reaction order with respect to either component of the redox pair is equal to 0,5 or reasonably less than 0,5, depending on whether or not the initiating component in question is present in the system in excess compared to its counterpart in the redox combination. Variable monomer exponents, largely dependent on [BZ2O2], characterize the redox photopolymerization process. The monomer exponent value, unity at [BZ2O2] = 0, progressively decreases with increasing [BZ2O2] (non-ideal kinetics). The rate enhancing effect of the solvent pyridine is more prominent at higher [BZ2O2]. The kinetic nonidealities in each case were further analyzed and interpreted in terms of (a) primary radical termination and (b) degradative initiator transfer. Relative effects of the variation of the level of dilution with pyridine were also analyzed.
    Additional Material: 10 Ill.
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  • 5
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The possibility of quantitative estimation of carboxyl groups in polymers by the dyeinteraction method developed in this laboratory has been investigated. The benzene extract of rhodamine 6Gx from a buffer of pH 10 under specified conditions has been used as the reagent. The estimation has been made by colorimetric measurement at 515 mμ of the color developed by mixing a solution of the polymer in benzene with the reagent. Copolymers of styrene (or methyl methacrylate of vinyl acetate) with acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or maleic anhydride at varying M1:M2 ratios in the 100:1 composition range have been prepared, and the monomer reactivity ratio r1 (which under such conditions becomes equal to the ratio of the mole-per cent of carboxyl in the feed to that in the copolymer) has been determined. The result agrees fairly well with the value of r1 reported in the literature. This indicates that the proposed method is capable of estimating fairly accurately the carboxyl groups or endgroups present in a polymer chain.
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aqueous polymerization of MMA was kinetically studied using separately two complexes of sulfur dioxide as initiators, namely, quinoline-sulfur dioxide (Q-SO2) complex and tetrahydrofuran-sulfur dioxide (THF-SO2) complex. In each case the initiator exponent was 0,5 and the monomer exponent was 1,5. Kinetic data, inhibitory effect of hydroquinone, and incorporation of sulfoxy end groups in the polymers indicate a radical mechanism of polymerization with first order dependence on monomer for the rate of initiation while termination appears to take place bimolecularly.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photopolymerization of MMA was carried out at 40°C in bulk and in diluted systems using quinoline-chlorine (Q-Cl2) C.T. complex as the photoinitiator. Bulk polymerization followed normal free radical kinetics (initiator exponent = 0,5) for [Q-Cl2] 〈0,0015 mol.1-1. In diluted systems, variable monomer exponents were observed, ranging from slightly above 1 to 2,7, depending on the nature of the solvent (benzene, carbon tetrachloride, chloroform, chlorobenzene, acetone, dioxane, THF and DMF). Initiator exponent was ≤0,5 in diluted systems and it even became practically equal to zero depending on the nature of solvent and the level of dilution. The kinetic non-ideality in diluted systems was explained on the basis of solvent-retardation and initiator-termination via degradative chain transfer involving solvent-modified initiating complexes and chain radicals. The actual initiating complex appeared to be the (Q-Cl2)-monomer complex formed instantaneously in situ on addition of Q-Cl2 complex to the monomer.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Flexural properties, impact energy, heat deflection temperature, and resistance to thermal and hydrothermal degradation of composites based on E-glass and N-glass fibers as the reinforcing agents, and epoxy, unsaturated polyester, phenolic, and epoxy-phenolic resin systems as the matrix materials were studied and compared. As a reinforcing agent E-glass fiber is superior to N-glass fiber, particularly with respect to development of flexural strength and modulus, impact strength, and thermal resistance; N-glass fiber, however, imparts to the composites substantially higher resistance to hydrothermal degradation under boiling conditions in different chemical environments. For use of both E-glass and N-glass fibers as reinforcing agents, the general order of resistance to hydrothermal degradation for the composites based on different matrix resins is epoxy 〉 phenolic 〉 unsaturated polyester resin. Incorporation of a low dose of a rubbery polymer, such as styrene butadiene rubber (0.1-0.2%) and liquid polybutadiene (0.5-0.75%), in unsaturated polyester resin as the matrix resin measurably enhances impact energy of the composite. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
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  • 10
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A dye partition method for the determination of hydroxyl endgroups in poly(methyl methacrylate) samples prepared in aqueous media with the use of hydrogen peroxide as the photoinitiator has been described. The dried polymers were treated with chlorosulfonic acid under suitable conditions whereby the hydroxyl endgroups present in them were transformed to sulfate endgroups. Spectrophotometric analysis of sulfate endgroups in the treated polymers was carried out by the application of the dye-partition technique developed for the purpose, and thus a measure of hydroxyl endgroups in the original polymers was obtained. H2O2, in the concentration range of 0.004-0.1M, was found to incorporate an average of nearly 1 OH endgroup per polymer chain.
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