ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Digitale Medien

Polyisobutylene-containing block polymers by sequential monomer addition. IV. New triblock thermoplastic elastomers comprising high Tg styrenic glassy segments: Synthesis, characterization and physical propertiesFor Parts I and II of this series, see Ref. 2; For Part III, see Polym. Prepr., 23 (1), 310 (1991); Part LXV of the series of Living Carbocationic Polymerization. (1992)

Puskas, J. E. ; Kaszas, G. ; Kennedy, J. P. ; [weitere]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 41-48

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0887-624X

Schlagwort(e): thermoplastic elastomer ; carbocationic polymerization ; polyisobutylene ; living polymerization ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: New linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert-ether (dicumyl methyl ether) initiator in conjunction with TiCl4 coinitiator in CH3Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at -80°C. After the living narrow molecular weight distribution PIB midblock ($\[\bar M_n\]$ = 1.1-1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p-methylstyrene (pMeSt), p-t-butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6-trimethylstyrene (TMeSt) and α-methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N-dimethylacetamide (DMA), TPEs with good mechanical properties (10-20 MPa tensile strength, 300-600% elongation) were prepared. The products exhibit a low and a high temperature Tg characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt-PIB-PSt triblock copolymers due to the higher Tgs (PpMeSt = 108, PptBuSt = 142 and PIn = 220-240°C) of the outer blocks. The Tg of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt-butylstyrene-co-indene) showed a single glassy transition Tg = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end-blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt-PIB-PSt triblock of similar composition.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pola.1992.080300105

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

2

Digitale Medien

Factors affecting microbial sulfate reduction by Desulfovibrio desulfuricans in continuous culture: Limiting nutrients and sulfide concentration (1992)

Okabe, S. ; Nielsen, P. H. ; Charcklis, W. G.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 40 (1992), S. 725-734

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0006-3592

Schlagwort(e): Desulfovibrio desulfuricans ; stoichiomentry ; kinetics ; microbial sulfate reduction ; sulfate limitation ; nitrogen limitation ; sulfide inhibition ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The effects of sulfate and nitrogen concentrations of the rate and stoichiometry of microbial sulfate reduction were investigated for Desulfovibrio desulfuricans grown on lactate and sulfate in a chemostat at pH 7.0. Maximum specific growth rates (μmax), half-saturation coefficients (Ksul), and cell yield (Yc/Lac) of 0.344 ± 0.007 and 0.352 ± 0.003 h -1, 1.8 ± 0.3 and 1.0 ± 0.2 mg/L, and 0.020 ± 0.003 and 0.017 ± 0.003 g cell/g lactate, respectively, were obtained under sulfate-limiting conditions at 35°C and 43°C. Maintenance energy requirements for D. desulfuricans were significant under sulfate-limiting conditions. The extent of extracellular polymeric substance (EPS) produced was related to the carbon: nitrogen ratio in the medium. EPS production rate increased with decreased nitrogen loading rate. Nitrogen starvation also resulted in decreased cell size of D. desulfuricans. The limiting C : N ratio (w/w) for D. desulfuricans was in the range of 45 : 1 to 120 : 1. Effects of sulfide on microbial sulfate reduction, cell size, and biomass production were also ivestigated at pH 7.0. Fifty percent inhibition of lactate utilization occurred at a total sulfide concentration of approximately 500 mg/L. The cell size of D. desulfuricans decreased with increasing total sulfide concentration. Sulfide inhibition of D. desulfuricans was observed to be a reversible process. © 1992 John Wiley & Sons, Inc.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260400612

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

3

Digitale Medien

Effects of temperature and phosphorous concentration on microbial sulfate reduction by Desulfovibrio desulfuricans (1992)

Okabe, S. ; Characklis, W. G.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 39 (1992), S. 1031-1042

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0006-3592

Schlagwort(e): D. desulfuricans ; sulfate reduction ; phosphorous limitation ; kinetics ; stoichiometry ; temperature effect ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The effects of temperature and phosphorous concentration on the rate and the extent of microbial sulfate reduction with lactate as carbon and energy source were investigated for Desulfovibrio desulfuricans. The continuous culture experiments (chemostat) were conducted at pH 7.0 from 12 to 48°C. The maximum specific growth rate (μmax) was relatively constant in the range 25°C-43°C and dramatically decreased outside this temperature range. The half-saturation coefficient was minimum at 25°C. Cell yield was highest in the optimum temperature range (35°C-43°C) for growth. Maintenance energy requirements for D. desulfuricans were not significant. Two moles of lactate is consumed for every mole of sulfate reduced, and this stoichiometric ratio is not temperature dependent. Steady state rate and stoichiometric coefficients accurately predicted transient behavior during temperature shifts. The extent of extracellular polymeric substance (EPS) is related to the concentration of phosphorous in the medium. EPS production rate increased with decreased phosphorous loading rate. Failure to discriminate between cell and EPS formation by D. desulfuricans leads to significant overestimates of the cell yield. The limiting C:P ratio for D. desulfuricans was in the range of 400:1 to 800:1.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bit.260391007

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

4

Digitale Medien

Frequency and molecular-mass-dependent nonexponential proton NMR relaxation in polymer melts (1992)

Hiller, W. G. ; Schneider, H. ; Fedotov, V. D.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 931-942

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0887-6266

Schlagwort(e): nuclear magnetic resonance (NMR) relaxation in polymer melts ; relaxation of proton NMR processes in melts (theory) ; chain motions and NMR relaxation in melts ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: A theoretical treatment of the nonexponential relaxation behavior of the different proton nuclear magnetic resonance (NMR) relaxation processes in polymer melts is presented. Formulas are derived for a three-component model given by two versions and a homogeneous distribution of correlation times. The theoretical results were tested with measurements of T1, T2e, and T2 as functions of frequency and molecular mass in linear fractionated polyethylene samples. While the T1 relaxation always yields exponential magnetization decays, the T2e and T2 measurements show biexponential relaxation behavior. From the calculations it was found that the correlation time of the local motion is independent of the molecular mass, whereas the correlation time of the slowest motional process increases with M2.8w for the three-component model and with M2.2w for the distribution of correlation times, respectively. © 1992 John Wiley & Sons, Inc.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/polb.1992.090300901

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

5

Digitale Medien

On the oxidation of γ′-Fe4N1-x layers; redistribution of nitrogen (1992)

Somers, M. A. J. ; Kooi, B. J. ; Sloof, W. G. ; [weitere]

Chichester [u.a.] : Wiley-Blackwell

Surface and Interface Analysis 19 (1992), S. 633-637

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0142-2421

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Physik

Notizen: Iron nitride (γ-Fe4N1-x) layers produced by gaseous nitriding of pure iron in an NH3/H2 mixture at 843 K were gaseously oxidized at 673 K in pure O2. During oxidation an ε-Fe2N1-y layer developed between a magnetite (Fe3O4) scale and the parent γ′-nitride layer. Porosity was observed in the oxide-adjacent part of the ε-grains. Scanning Auger microscopical analysis and electron probe microanalysis showed (1) that the occurrence of the ε-nitride layer is associated with a locally higher nitrogen content, (2) that no nitrogen is incorporated in the oxide layer and no oxygen is dissolved in the nitride layer and (3) that a nitrogen concentration-depth gradient occurs which corresponds to a change of about 1 at.% N over the thickness of the ε-layer. From a thermodynamical point of view, formation of N2 gas during the oxidation of γ′-nitride is more likely to occur than formation of ε-nitride; the latter reaction appears to be kinetically favoured. Quantitative analysis of the nitrogen redistribution suggests that some of the nitrogen atoms released by conversion of γ′-nitride into magnetite are transformed into N2 which is present in the pores near the oxide/nitride interface.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/sia.7401901118

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

6

Digitale Medien

Analysis of the deformation of polypropylene hot-tool butt welds (1992)

Gehde, M. ; Bevan, L. ; Ehrenstein, G. W.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 32 (1992), S. 586-592

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0032-3888

Schlagwort(e): Chemistry ; Chemical Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Thin microtomed samples from hot-tool butt welds of polypropylene pipes are subjected to uniaxial tensile stress using a specially built instrumented microtesting machine. The deformation of the interface between the weld and the bulk polymer is measured by an optical method. An analysis of these measurements is carried out using the finite element method, and contours of the effective stress are obtained. There is a steep stress gradient at the junction of the weld flash and the bulk polymer, although the stress concentration factor is relatively low. The stress is essentially constant in the bulk polymer apart from the region near the weld zone. Tests on samples without the weld flash show that the maximum stress occurs within the weld zone. This is consistent with long-term tests on larger samples, where the fracture is found to initiate within the weld. The method of analysis enables the stress-strain response of the weld material to be determined.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pen.760320904

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

7

Digitale Medien

Synthesis and calorimetric curing study of amino-terminated PEEK oligomers (1992)

Corfield, G. C. ; Wheatley, G. W. ; Parker, D. G.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 845-849

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0887-624X

Schlagwort(e): PEEK ; reactive oligomer ; crosslinking ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Amino-terminated polyetheretherketone (PEEK) oligomers were prepared by the condensation of 4,4′-difluorobenzophenone and hydroquinone in the presence of a calculated excess of m-aminophenol endblocker. The molecular weight of the oligomer was controlled by the manipulation of the ratio of difluoride to hydroquinone with the appropriate stoichiometric amount of m-aminophenol ensuring amino termination. The thermally induced self-crosslinking of these oligomers was studied by differential scanning calorimetry (DSC). Curing was found to be quite slow, taking up to 1 h to reach completion at 668 K. Cured materials were all completely amorphous in contrast to the semi-crystalline starting material. The limiting Tg reached on curing was found to be proportional to the percentage of reactive terminal groups, as would be expected.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pola.1992.080300515

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

8

Digitale Medien

Synthesis and properties of an easy-processable bismaleimide thermoset resin (1992)

Winter, H. ; Mostert, H. A. M. ; Tholen, M. G. W.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 45 (1992), S. 451-459

zur Merkliste hinzufügen auf der Merkliste

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: Reaction of methylenedianiline and maleic anhydride in acetone, followed by cyclodehydration in the presence of acetic anhydride and 1,4-diazabicyclo [2.2.2] octane as a catalyst, affords a mixture of compounds, Desbimid, with maleimide, isomaleimide, and acetamide groups. Dissolution of this mixture in styrene and 2-hydroxyethyl methacrylate results in clear liquid resins. The viscosity of the formulated resins ranges from 100-1700 mPas at 25°C depending on the concentration of Desbimid. These systems can be processed and cured at ambient temperatures until demoulding and postcured at temperatures up to 200 or 250°C. The flexural modulus, flexural strength, and elongation at break of a number of cured formulations are found between 3500-3800 N/mm2, 90-115 N/mm2, and 2.7-3.5%, respectively.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1992.070450310

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

9

Digitale Medien

Identification of cyclobutane-type dimers of substituted cinnamic acids by gas chromatography/mass spectrometry (1992)

Stewart, D. ; Robertson, G. W. ; Morrison, I. M.

New York, NY : Wiley-Blackwell

Rapid Communications in Mass Spectrometry 6 (1992), S. 46-53

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0951-4198

Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Physik

Notizen: Substituted cinnamic acids were dimerized, under fluorescent or UV light, as a glassy coating on a vial then subsequently analysed by GC/MS. Mass Spectrometric analysis of the dimers formed by each acid allowed the assignment of the dimer as a truxillic or truxinic structure since these structures had distinctive fragmentation patterns; the breakdown of the truxillic acids involves a McLafferty rearrangment before fragmentation occurs, whereas the truxinic acids, which have both carboxy groups on one side and both aromatic groups on the other, fragment asymmetrically to give characteristic stilbene and dicarboxylate fragments. It is apparent from the results of the dimerization of the lcinnamic acids that, under the conditions used here, if the monomeric acid had the capacity for hydrogen bonding using the ring substituent as well as the carboxy group, the dimerization products would be overshelmingly truxillic in structure. However, if only the carboxy group could hydrogen bond, the products would be almost exclusively traxinic in structure.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/rcm.1290060110

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext