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  • 1
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel antibiotic, PD 121,222, was isolated from a complex of pluramycin-like compounds containing mostly kidamycin and neopluramycin. Spectral analyses showed that this compound is the 14,16-dihydroxy analog of rubiflavin A.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 583-591 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: An analytical methodology was developed capable of describing interrelations between thermal processing and polymer structure for thermoplastic based composite laminates. Specifically, this modeling methodology was used to describe experimental results generated with a specially designed match die quench mold by processing both neat PEEK polymer and carbon fiber reinforced laminate samples at different cooling rates. The developed model accurately predicted temperature profiles for PEEK laminates of different thicknesses, under normal as well as extreme quenching conditions of 114°C/s. surface cooling rates that are possible to generate with the quench mold. In general, the modeling methodology is capable of predicting a part's thermal profile during processing in terms of the composite's microscopic intrinsic properties (fiber and matrix), composition, and lamina orientation. Furthermore, by coupling to the thermal profile description, a previously developed crystallization kinetics model for PEEK polymer and its carbon reinforced composite, a quantitative description of structural development during processing was obtained. Thus, with this analytical methodology, a skin-core crystallinity profile, where the crystallinity varies with part-thickness as a result of uneven cooling experienced during processing, was predicted both for the neat PEEK polymer and its carbon reinforced laminate forms. Finally, the developed methodology clearly established the interplay of both microscopic heat transfer and kinetics of crystallization/solidification of the matrix that must be accounted for in predicting the final structure of a carbon fiber reinforced laminate that will, in turn, govern microscopic and macroscopic performance.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 634-639 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Neat poly(ether-ether-ketone) (PEEK) and carbon fiber reinforced PEEK (APC-2) specimens were prepared using a variety of cooling rates to achieve a range of crystallinities. Amorphous specimens were exposed to a variety of fluids to determine the penetrant types which are able to strongly influence the material. This allowed the estimation of the solubility parameter and hydrogen bonding index for PEEK to be 9.5 and 3.1, respectively. Methylene chloride was used to investigate the kinetics of penetrant sorption. The data demonstrated Case II behavior, with the initial crystallinity having a pronounced effect on both the kinetic and equilibrium data. Accordingly, a model was proposed capable of describing the sorption level and penetration depth as a function of time given the sample crystallinity and sorption temperature. With Case II behavior there was no difference in the sorption kinetics of neat and fiber reinforced PEEK. Finally, the dynamic mechanical properties measured during sorption were found to be dependent on the sorption process.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 375-381 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The tacticity of poly(cyclohexyl α-chloroacrylate) (PCCA) was studied by 500 MHz 1H and 25 MHz 13C NMR spectroscopy. The influence of the polymer configuration was observed at three different carbon resonances: The backbone methylene carbon, the carbonyl carbon and the quaternary carbon. Tetrad tacticities of PCCA measured from the resonance of the backbone methylene carbon were in good agreement with tetrad values obtained by 1H NMR. The polymer obtained was syndiotactic rich and obeyed Bernoullian statistics in its tacticity distribution.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1309-1317 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Acetylene was polymerized by (η-Cp)2Ti(PMe3)2 at room temperature to give predominantly trans-polyacetylene. All properties are within the ranges reported for polyacetylene produced with Ti(OBu)4/AlEt3 as catalyst.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 1 (1986), S. 155-158 
    ISSN: 0269-3879
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Endogenous opioid receptoractive peptides in the cerebrospinal fluid (CSF) of human controls and in those patients diagnosed as having senile dementia of the Alzheimer's type (SDAT) are measured with a radioreceptorassay following HPLC separation. [3H]Etorphine is the ligand used to detect in the HPLC fractions the presence of those endogenous peptides that preferentially interact with several opioid receptors. The RRA uses a receptor-rich P2 fraction extracted from a canine limbic system. The total opioid peptide content found in the HPLC fractions 6-20 (to avoid salts in fractions 1-5) of SDAT CSF (383 ± 187 pmol ME-equivalents per ml CSF) is significantly higher than the corresponding total from patients with no known neurological disorders (89.1 ± 46.3 pmol ME-equivalents per ml).
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 111-133 
    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 systematic four-stage investigation of eight unpigmented coating formulations, including three vinyl, two polyurethanes, and three epoxy systems was done to provide baseline structural information upon which an improved understanding and an optimization of protective coatings can be founded. First, the results from dynamic mechanical measurements are provided and discussed for the base polymer component in each coating system. Second, the effects of humidity on the dynamic mechanical properties of these base polymers were determined at room temperature. The extent of property degradation was monitored by calculating the Tg depression with increased humidity, assuming a temperature-humidity superposition. The extent of degradation, as monitored by the Tg, was found to correlate directly with the level of hydrogen bonding in these coatings. Third, the influence of typical coating additives (a TCP plasticizer and a rosin hardener) on the properties of two of the vinyl coating systems was investigated. In the final stage, the synergistic effects of absorbed moisture and these additives on the coatings properties were investigated at room temperature. Increases in the concentration of these additives was found to magnify the degradation effect of increased humidity. This magnified degradation has been assigned to increased water absorption with increases in the concentration of either of these additives.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1155-1167 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dielectric spectroscopy was used to monitor the curing process of two epoxy resin systems. The basic system (system I) consisted of DGEBA (a difunctional epoxy) and a polyamide in a 50-phr mixture. In addition, a comparative analysis was performed on a high-performance resin system (system II) used primarily in unidirectional composite applications. This system contained TGDDM (a tetrafunctional epoxy) and DDS (a tetrafunctional amine) in a 25-phr mixture. The dielectric data were obtained using a simple yet functional sample cell electrode designed and constructed in the laboratory. For system I, isothermal dielectric data were used to determine apparent activation energies for the temperature range from 22 to 70°C. The data showed that the activation energy was a function of temperature and increased as the temperature of the cure increased. This indicated that the reaction mechanism was also a function of temperature. For system II, data were collected between 140 and 190°C and an overall activation energy for that temperature range was determined. The overall activation energies for both systems, calculated using dielectric spectroscopy, compared favorably to those obtained using differential scanning calorimetry. Also, using a wider frequency range (240 Hz to 2 MHz), Argand diagrams were constructed and modeled with the Cole-Cole empirical equation for systems with a distribution of relaxation times. This justified the calculation of average relaxation times, which could then be related to the bulk physical properties of the polymer, such as viscosity. Modified Argand diagrams, where ε″ is plotted against ε′ at one frequency as a function of time, were also constructed, which aided in the understanding of the curing processes for these thermosetting systems.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 1387-1400 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dynamic mechanical measurements had been made on polyurethanes of a range of hard segment content (HSC) obtained from α,ω-dihydroxy derivatives of polydioxolane, polybutyltrioxocane, and poly(propylene oxide) of 2000-12,000 MW coupled with MDI and TDI with hydroxyethyl phthalamide chain extenders. N-methylated chain extender was used to investigate the effect of hydrogen bonding. A broad γ transition was observed between -100 and -115°C attributable to the local motion of methylene sequences with a distribution of relaxations. The β-transition between -55 and -72°C is influenced by the degree of hydration; the α-transition occurs at nearly the same temperatures for all the TPEs, independent of HSC and thermal history. The magnitude of the loss tangent peak is nearly proportional to the soft segment content; the peak corresponds to the glass transition. An α-transition at higher temperature is sensitive to the structure of soft segment, HSC, and thermal history. It is probably associated with the melting of some weakly ordered regions in the soft domain. The hard domain counterpart was observed at the next higher temperature as the ∊-relaxation. The final large loss of storage modulus occurs at temperatures much below the melting transition.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 2903-2917 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Acid-catalyzed degradation of poly(2-butyl-1,3,6-trioxocane) (1) has been studied. With ethyl tosylate as the catalyst, the cyclic monomer 2 was the major product. The minor products are cis and trans isomers of C3H7CH=CH—OCH2CH2OCH2CH2OH, and three stereoisomers of C3H7CH=CH—OCH2CH2OCH2CH2O—CH=CH—C3H7 elucidated by 1H and 13C NMR, IR, electron impact and chemical ionization MS, and in the case of 2 also by comparison with an authentic sample. With 98% H2SO4 as the catalyst 2 is only a minor product. The major products are diethylene glycol, valeraldehyde, and 1,4-dioxane with some 2-butyl-1,3-dioxolane. Capillary GC/mass spectrometry led to identification of the following less abundant products: tri-n-propylbenzene, α,β-unsaturated aldehydes, and cyclic dimer. The products of H2SO4-catalyzed decomposition of polymer were also obtained by heating monomer 2 with H2SO4. A detailed mechanism for the formation of the eight-member ring 2 in the decomposition is proposed which involves unzipping proceeds via open carbocation intermediates. According to the principle of microscopic reversibility, the same open carbocation is the propagating species in the polymerization of 2 under similar conditions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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