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  • 1
    Digitale Medien
    Digitale Medien
    Novel polystyryl resins for size exclusion chromatography (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2029-2038 
    Details
    ISSN: 0887-624X
    Schlagwort(e): 1,2-bis(p-vinylphenyl)ethane ; divinylbenzene ; crosslinker ; network structure ; size exclusion chromatography resins ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New size exclusion chromatography (SEC) resins based on a crosslinker having independent vinyl groups have been produced and compared with SEC resins based on divinylbenzene-55 (DVB). 1,2-Bis(p-vinylphenyl)ethane (p,p-BVPE) and its meta-isomers were suspension-copolymerized with p-methylstyrene in the presence of different porogens to give particles of about 5 μm average diameter. The porous particles were slurry-packed into stainless steel columns for SEC evaluation. Calibration curves were obtained using narrow disperse polystyrene standards with molecular weights ranging from 580 to 3,040,000. The calibration curves for the new BVPE resins covered wider useful molecular weight ranges than those for comparable divinylbenzene resins. Particle size, surface morphology and the properties of pores were studied using a Coulter Multisizer II, scanning electron microscopy, nitrogen adsorption, and mercury porosimetry. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1994.080321104
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  • 2
    Digitale Medien
    Digitale Medien
    Poly(N-isopropylacrylamide). I. Interactions with sodium dodecyl sulfate measured by conductivity (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 957-962 
    Details
    ISSN: 0887-624X
    Schlagwort(e): poly(N-isopropylacrylamide) ; sodium dodecyl sulfate ; polymer-surfactant complex formation ; micelle formation ; phase separation temperature ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conductometric titration of poly(N-isopropylacrylamide) (polyNIPAM) with sodium dodecyl sulfate (SDS) gave two apparent transitions labeled C1 and C2. The C1 transition was independent of polyNIPAM concentration in the 0.05-0.3 wt % range, whereas C2 was proportional to the polymer concentration. C1 corresponded to the onset of binding of surfactant with polymer. Arguments based on a simple mass action model for micellization are presented to show that C2, the second transition, is not due to any simple explanation such as being the point above which only free micelles are formed with surfactant addition. The cloud point of polyNIPAM increased with the amount of bound surfactant. This was attributed to electrostatic contribution of bound sulfate groups to the increased solubility of polyNIPAM. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1993.080310414
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  • 3
    Digitale Medien
    Digitale Medien
    High-yield synthesis and characterization of 1,2-bis(p-vinylphenyl)ethane (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2023-2027 
    Details
    ISSN: 0887-624X
    Schlagwort(e): 1,2,-bis(p-vinylphenyl)ethane ; crosslinker ; network structure ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quantitative synthesis and complete characterization of 1,2-bis(p-vinylphenyl)ethane (p,p-BVPE) and its meta-, para-mixed isomers are reported. These crosslinkers copolymerize randomly with p-methylstyrene, leading to random crosslink distributions. The crosslinkers are prepared by Grignard coupling of (m,p)-vinylbenzyl chloride in tetrahydrofuran at low temperature to give the statistical mixture of m,m-, m,p-, and p,p-isomers in quantitative yield. Pure p-vinylbenzyl chloride is converted to pure p,p-BVPE. p,p-BVPE has also been separated from the mixture of isomers. The isomers are characterized by elemental analysis, mass spectrometry, 1H-NMR, and 13C-NMR and by reversed-phase HPLC. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1994.080321103
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  • 4
    Digitale Medien
    Digitale Medien
    Modelling of crosslinking and cyclization in free-radical copolymerization of vinyl/divinyl monomersDedicated to Dr. Milan Lazár on the occasion of his 65th birthday. (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 2 (1993), S. 587-604 
    Details
    ISSN: 1018-5054
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Tobita-Hamielec kinetic model of the crosslink density distribution is further elaborated and extended to incorporate divinyl loop formation. Divinyl loop formation, primary and secondary cyclization, and their effects on the elastically effective crosslink density distribution are extensively examined as a function of cyclization parameters and double bond reactivities. Under conditions of equal double bond rectivity and negligible cyclization, primary chains born at different conversions have the same crosslink density. The variance of the crosslink density distribution is mainly due to unequal reactivities of double bonds and secondary cyclization. Divinyl loop formation and primary cyclization contribute neither to gelation nor to network elasticity and have an insignificant effect on the variance of the crosslink density distribution.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mats.1993.040020406
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  • 5
    Digitale Medien
    Digitale Medien
    Experimental investigation of vinyl chloride polymerization at high conversion - conversion and tracer response relationships (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2327-2347 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A model for suspension polymerization which relates the conversion of vinyl chloride monomer (VCM) to polymerization conditions and a tracer response measured by online gas chromatography has been developed. This model can be used to determine monomer conversion with measurements of tracer response by gas chromatograph. A series of experiments using inert mixtures of H2O/PVC/VCM/n-butane and using suspension polymerization of VCM with n-butane as tracer were carried out to evaluate the model. The solubility of n-butane in vinyl chloride was determined in the temperature range 40-70°C. The solubility of n-butane in polyvinylchloride (PVC) was estimated using nonlinear regression comparing model and experimental data for both inert mixtures and for suspension polymerization. Correlations of the solubility constants of n-butane in VCM and PVC, respectively, were obtained from the experimental data. Under the present experimental conditions, conversions can be measured online every 7-8 min using the n-butane tracer method.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070410934
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  • 6
    Digitale Medien
    Digitale Medien
    Epoxy-amine oligmer production (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 867-890 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The production of an adduct epoxy-polytheramine with free epoxy groups is anlyzed. Diffrential scanning caloriemetry (DSC), infrared spectroscopy (IR), titration of functional groups, and gel permeation chromatography (GPC) were used to study the reaction of bisphenol A diglycidyl ether (DER 332) with an aliphatic hindered polyether-amine (Jeffamine D-2000). The general kinetic model derieved by Riccardi and Williams1 is extended to generate equations for nonstoichiometric epoxy-amine systems. The parameter N, which gives the reactivity ratio between the secondary and primary amine groups, was obtained from a linear regression obtained at various temperature levels. the activation energies of the epoxy amine reaction catalyzed by OH groups and the noncatalytic one were determined. According to experimental evidence, the etherfication reaction may be neglected. From dynamic experiments in DSC a heat of reaction of 25 kcal/eq was obtained. The weight average molecular weight of different epoxy-amine oligomers with high ratio of epoxy-amine were compared with those theoretically predicted using an statistical structural model (SSM). This model utilizes a kinetic scheme and a recursive method to determine statistical parameters and it was applie before to phenolic resins 2,3 epoxy-amine systems.4 Depending on the required ologomer characteristics, the best production policy can be established using he data supplied in this report.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070400521
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  • 7
    Digitale Medien
    Digitale Medien
    Kinetic model for short-cycle bulk styrene polymerization through bifunctional initiators (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 629-641 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A model describing the kinetics of bulk styrene polymerization through bifunctional initiators has been developed. The diffusion-controlled propagation and termination reactions at high monomer conversions are modeled with the free volume theory for polymer solutions. Three different commercially available bifunctional initiators were experimentally evaluated for a wide range of polymerization conditions to study the effect of the reaction rate on the molecular weight and molecular weight distribution. The model predictions for the same polymerization conditions show excellent agreement with the experimental data, for the whole range of conversions, for both reaction rate and molecular weight distribution development, under all the conditions tested. It is demonstrated throughout this study that high molecular weights, very high reaction rates, and narrow molecular weight distributions can be achieved simultaneously by using bifunctional initiators. A comparison between monofunctionally initiated systems with the bifunctionally initiated ones shows that short-cycle reactions with reductions in polymerization time of up to 75% may be achieved with the bifunctional initiators for a wider range of conditions without significantly affecting the molecular weight and molecular weight distribution of the final product.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1991.070420309
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  • 8
    Digitale Medien
    Digitale Medien
    Experimental investigation of vinyl chloride polymerization at high conversion - reactor dynamics (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1259-1269 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A series of suspension polymerizations of vinyl chloride monomer (VCM) was carried out in a 5-L pilot plant reactor over the temperature range, 40-70°C. The reactor pressure and monomer conversion were monitored simultaneously every 7-8 min. The critical conversion Xf, at which the liquid monomer phase is consumed, was considered to occur when the reactor pressure fell to 98% of the vapor pressure of VCM for suspension at the polymerization temperature. The reactor model predictions of pressure are in excellent agreement with the experimental data over the entire conversion and temperature ranges studied. The mechanism of reactor pressure development for VCM suspension polymerization is discussed herein in some detail. For isothermal batch polymerization, the reactor pressure falls in two stages due to the effect of polymer particle morphology on pressure drop. The first stage is due to the volume increase of the vapor phase as a result of volume shrinkage due to conversion of monomer to polymer. The monomer phase is not yet consumed at this stage, but it is trapped in the interstices between primary particles creating a mass transfer resistance; therefore, the reactor pressure drops slowly. The second stage is due to both the volume increase of the vapor phase and to the monomer in the vapor phase diffusing into the polymer phase because of the subsaturation condition with respect to monomer in the polymer phase. The reactor pressure drops dramatically with an increase in monomer conversion at this stage. The present model can be used to predict reactor dynamics during suspension polymerization under varying temperature and pressure conditions.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1991.070430707
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  • 9
    Digitale Medien
    Digitale Medien
    Limitation and evaluation of the two-broad standard (TBS) method of calibration of aqueous SEC (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 875-892 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Few years ago, the two broad standard method of molecular weight (MW) calibration was proposed1 and the presence of negative σ2 (peak dispersion coefficient) was found to be somewhat disturbing. The limitation of the method was not specified. Since large negative values of σ2 cannot be tolerated, herein is reported another type of instrumental spreading function for which the method may seem to apply, and an evaluation of this method. In its evaluation, plots of loge (intercept of a linear molecular weight calibration curve), that is, loge(D1) vs. the corresponding slope of the molecular weight calibration curve, D2, which were found to be linear, were used. The systems employed were Dextran/Corning controlled porous glass (CPG-10) packing in well-chosen mobile phase.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070390409
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  • 10
    Digitale Medien
    Digitale Medien
    Molecular weight characterization of poly(acrylamide-co-sodium acrylate). I. Viscometry (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2081-2093 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Mark-Houwink constants for polyacrylamide and poly(acrylamide-co-sodium acrylate) in 0.2M Na2SO4 were measured using eight fractionated samples of polyacrylamide and 26 hydrolyzed polyacrylamide samples. The dependence of K and a on the copolymer compositions was found for the range of acrylate content 6 ∼ 40 mol %. A relationship between intrinsic viscosity and acrylate content in the form of square root law was found. Molecular weights of copolymer samples with various compositions were estimated using viscometry with Mark-Houwink equations established in this work. The molecular weights of narrow MWD copolymer samples could be measured with an error of ±5%, whereas those of broad MWD copolymer samples with an error of ±8%.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1991.070420736
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