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  • Articles: DFG German National Licenses  (7)
  • Electronic Resource  (7)
  • 1990-1994  (7)
  • Polymer and Materials Science  (4)
  • Brassica cultivars  (1)
  • Molecular interaction  (1)
  • N-vinyl pyrrolidone  (1)
Source
  • Articles: DFG German National Licenses  (7)
Material
  • Electronic Resource  (7)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 20 (1991), S. 531-538 
    ISSN: 1572-8927
    Keywords: Molecular interaction ; excess Gibbs free energy of mixing ; ideal associated model ; equilibrium constants ; thermodynamics of mixtures ; binary mixtures ; interactions in solutions ; applicability of Flory theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The excess Gibb's free energy of mixing, GE, for ethyl iodide+toluene at 25°C have been obtained from the measured vapor pressuure data. The HE and GE values for ethyl iodide+toluene are positive throughout the ethyl iodide concentration range and GE〉HE. The results have been analyzed in terms of Flory and ideal associated model theory of nonelectrolyte solutions. It has been observed that the ideal associated model approach which assumes the presence of AN and A2B molecular species describes well (within±10 J-mol−1 in the worst case) the general dependence of HE on XA (mole fraction of ethyl iodide) over the whole composition range for ethyl iodide+toluene mixtures. The equilibrium constants for A+A⇆ AB and 2A+B⇆A2B reactions along with the enthalpies of formation of AB and A2B molecular species have been calculated.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 85 (1993), S. 770-776 
    ISSN: 1432-2242
    Keywords: Intergeneric hybrids ; Bridge cross ; Alloplasmics ; Diplotaxis ; Brassica cultivars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Intergeneric hybrids were produced between Diplotaxis siettiana and Brassica campestris through embryo rescue. The hybrids were completely pollen sterile and backcrosses with pollen of B. campestris did not yield any seeds. Induction of colchiploidy restored pollen fertility and backcross pollinations yielded viable seeds. Cytological details of the hybrid, amphidiploid and backcross progenies were studied. Both pollen-sterile and pollen-fertile plants have been obtained in backcross 2 progeny. This hybrid (D. siettiana x B. campestris) was used as a bridge cross to transfer the cytoplasm of D. Siettiana to two other incompatible cultivars of Brassica — B. juncea and B. napus. Pollinations of the amphidiploid (D. siettiana x B. campestris, 2n = 36) with pollen of B. juncea/B. napus readily produced seeds without embryo rescue. These hybrids were grown to flowering and their cytological details were studied. Seeds have been produced from backcross pollinations of both these hybrids with the pollen of the respective cultivars. The results clearly show the feasibility of producing alloplasmic lines in all the three oilseed brassicas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 268 (1990), S. 645-648 
    ISSN: 1435-1536
    Keywords: β-picolinium-p-chlorophenacylide ; α-α azobisisobutyronitrile ; N-vinyl pyrrolidone ; dilatometry ; retarder ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract β-Picolinium-p-chlorophenacylide (β-PCFY) acts as a retarder for polymerization of N-vinyl pyrrolidone. The polymerization runs were carried out at 60°C using benzene as an inert solvent. The kinetic equation for the present system may be written asR p α[β-PCPY]−1.0 [AIBN]0.66[N-VP]1.0. The value of overall energy of activation for polymerization in presence and absence ofβ-PCPY was computed as 44.0 and 42.3 kJ mol−1, respectively. The inverse relationship ofR p and¯M v withβ-PCPY suggests thatβ-PCPY acts as a polymerization retarder. The retarding effect is also evidenced by higher initiator exponent value and higher value of energy of activation in presence of ylide. A mechanism is also proposed in which polymer propagating chain combines with one ylide component to give resonance stabilized radical.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 1-9 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der photo-oxidative Abbau von Blends aus Polyethylenterephthalat (PET) und Poly(2,6-dimethyl-1-1,4-phenylenoxid) (PPO) wurde untersucht, wobei die gegenseitige Beeinflussung beider Komponenten berüucksichtigt wurde. Im Temperaturbereich 30 - 100°C wurden die Auswirkungen der Segmentbeweglichkeit der Polymerketten ermittelt. Für kurze UV-Bestrahlung (365 nm) ist der Abbau diffionskontrolliert und kann mit der Theorie von Waite erklärt werden. Die Wechselwirkungen der Polymersegmente in den Blends beeinflussen auch die Diffusionskoeffizienten und die Aktivierungsenergie. Für PET in Blends verursacht eine höhere Aktivierungsenergie eine Abnahme des Kettenbruchs.
    Notes: Photo-oxidative degradation of blends of poly(ethylene terephthalate) (PET) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was studied considering the mutual influence of both components. The photo-oxidation of these systems was investigated in the temperature range 30-100°C to study the effects of segmental motion of polymer chains. For short time of UV-illumination at 365 nm the process is diffusion controlled and can be explained with the help of Waite's theory. The segmental interactions of polymer segments in the blends also affect the diffusion coefficients and the activation energy values. Higher values of the activation energy of PET in the blends cause a decrease of chain breaking.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 451-462 
    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: Tensile and impact properties of the ternary system polypropylene (PP)/ethylene propylene diene elastomer (EPDM)/glass fiber (GF) and the corresponding binary systems PP/EPDM blend and PP/GF composite are studied. Results are presented and analyzed as functions of compositional variables, viz., (i) matrix PP/EPDM blending ratio at constant GF loadings and (ii) GF loading at constant matrix blending ratios for the ternary system and (iii) EPDM content for PP/EPDM binary system and (iv) GF content for the binary system PP/GF, respectively. The role of individual components EPDM and GF in these mechanical properties is discussed and their combined effects are inspected at certain composition ranges. Theoretical analysis of tensile data is presented which reveals the effect of EPDM on the reinforcing effect of GF. Unlike the conventional role of an elastomer, increase of EPDM content in the presence of GF increases the modulus of the ternary system. Impact strength of the ternary system increases with increasing GF content both in the presence and absence of EPDM, showing a distinct minimum at matrix blending ratio PP/EPDM 90/10. Scanning electron micrographs of impact-fractured surfaces are presented to illustrate the dispersion of the two phases of the polyblend matrix, fiber alignment, and the fiber interface.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2595-2611 
    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: Melt rheological properties of the blend of isotactic polypropylene (PP) and ethylene propylene diene rubber (EPDM) at varying ratios and of the glass fiber (GF) filled PP and PP/EPDM blend by varying both GF loading and blending ratio of the polyblend matrix are studied. Rheological measurements at 220°C in shear rate range 101-104s-1 were made on a capillary rheometer. Scanning electron micrographs of the extrudates are presented to show the morphology and the alignment of the glass fibers with respect to the flow direction. Variations of pseudoplasticity index, melt viscosity, and melt elasticity with EPDM content in PP/EPDM blend, and with varying GF content at any given composition of the matrix in PP/EPDM/GF ternary system, in the studied range are presented and discussed. Resultes on melt viscosity and melt elasticity show (i) reduced effect of GF at high shear rates on these properties and (ii) upward deviation of melt viscosity versus shear rate curve at low shear rates. A change in flow behavior in presence of GF is observed around a critical shear rate 2 × 103 s-1 and is attributed to the difference of interaction of GF and the dispersed rubber droplets at high and low shear rates. Elastic recovery showed nonequilibrium behavior at low shear rates.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 729-734 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Zirconia has received special attention, mainly because of its high strength and toughness. However, there is some controversy about the time-dependent deterioration of its mechanical properties. To examine the change in mechanical properties of zirconia ceramics in vivo and in vitro, tetragonal zirconia polycrystal pieces were introduced into the medullary cavity of the tibia in Japanese rabbits and animals were sacrificed after 2, 4 and 6 weeks and 6, 12, and 30 mo, respectively. Alumina ceramic and hydroxyapatite (HAP) pieces were used as controls to investigate the differences in biocompatibility. Zirconia showed a bending strength of over 1000 MPa initially, and little time-dependent change in strength was found in both in vivo environments. x-Ray analysis showed little change in the transformation rate, i.e., less than 5 mol % in vivo and in vitro over a period of 3 years. To estimate time-dependent changes in zirconia over a longer period, zirconia pieces were placed in 95°C saline solution for over 3 years and their mechanical properties examined at chosen intervals. No serious decrease of bending strength was found over the 3-year period under these conditions. It is concluded that zirconia can be used clinically because it retains a bending strength of over 700 MPa under any experimental conditions for over 3 years. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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