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  • 1
    Electronic Resource
    Electronic Resource
    A biomaterial-based carbon fiber (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 147-163 
    Details
    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: Es wurde versucht, Sisalfasern zu kostengünstigen Kohlefasern zu carbonisieren. Vorbehandlung, Pyrolyse- und Carbonisierungsvorgang sowie Struktur und Eigenschaften der gebildeten Produkte wurden untersucht. Anwendungsmöglichkeiten für die aus Sisal hergestellten Kohlefasern mit mäßigen mechanischen Eigenschaften werden vorgeschlagen.
    Notes: An attempt to convert natural sisal fiber into low cost carbon fibrous materials was made. The pretreatment, pyrolysis and carbonization processes of raw sisal fiber as well as structure and properties of the resultant product were investigated. It was found that the sisal-based carbon fiber with moderate mechanical performance can be manufactured under the conditions applied. In addition, the application of the obtained sisal-based carbon fiber serving as functional material is presented.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052220111
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  • 2
    Electronic Resource
    Electronic Resource
    Polyradical distribution in free radical crosslinking of polymer chains (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2099-2104 
    Details
    ISSN: 0887-6266
    Keywords: molecular weight distribution ; polyradical ; gel ; polymer modification ; nonlinear polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Polymer coupling and theory of on-random crosslinking: an analytical solutionDedicated to Professor A. E. Hamielec on the occasion of his retirement (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 1105-1120 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gel formation is an important feature in free-radical polymer coupling. Due to the different possible combination reactivities of each polymer backbone radical, polymer chains are crosslinked in a non-random manner. Equations of the moments have been derived to predict the pregel molecular weight development and the crosslink density at gel point. This work provides an analytical solution for the differential equations. The model agrees with the Flory-Stockmayer gelation theory under the condition of random crosslinking. The magnitude of deviations from the classical theory for non-random crosslinking depends on the product of the radical termination reactivity ratios (r1r2), the ratio of the rate constants of backbone radical generation (k), the ratio of the weight-average chain lengths of primary polymers (y), and the polymer weight fractions (w2).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1996.040050606
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular weight distribution of metallocene polymerization with long chain branching using a binary catalyst systemDedicated to Professor A. E. Hamielec for his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 6 (1997), S. 793-803 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In metallocene polymerization, termination by β-hydride elimination generates polymer chains containing unsaturated vinyl groups at their chain ends. Further polymerization of these macromonomers produces branched polymers. Material properties of the branched polymers not only depend on molecular weight and branching density, but also on chain structure. This work presents analytical expressions to predict the bivariate distribution of molecular weight and branching density for polymer chains having dendritic and comb structures. It is shown that when a single metallocene catalyst is used the formation of dendritic polymers is favored with only a very small fraction of highly branched chains assuming comb structure. The use of a binary catalyst system is therefore proposed to obtain high content of comb polymers. One catalyst generates macromonomers and the other yields in-situ branching. It is found that the comb polymers give much narrower molecular weight distributions than dendritic polymers with same branching densities.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1997.040060409
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  • 5
    Electronic Resource
    Electronic Resource
    Long chain branching in ethylene polymerization using constrained geometry metallocene catalyst (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2409-2416 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report an experimental investigation on long chain branching (LCB) in ethylene polymerization with the Dow Chemical's constrained geometry catalyst system, CGC-Ti/TPFPB/MMAO, using a continuous stirred-tank reactor (CSTR) at 140°C, 3.45 × 103 kPa, and a mean residence time (τ) of 4 min. The effects of the catalyst (CGC-Ti) and co-catalyst (TPFPB and MMAO) concentrations on the catalyst activity, polymer molecular weight, and shear thinning were systematically examined. The boron cocatalyst had a great influence on the CGC activity. Increasing the ratio TPFPB/CGC-Ti from 0.66 to 5 gave ethylene propagation rates from 1.65 × 103 to 1.36 × 104 L · mol-1 · s-1. The addition of MMAO appeared to be essential, most likely acting as an impurity scavenger. The LCB polyethylenes showed enhanced shear thinning properties. The melt flow index ratios I10/I2 were in the range of 6.96 to 23.4, with the I2 of 0.172 to 0.681 g/10 min. The weight-average molecular weight Mw was correlated to I2 using a power equation within narrow I10/I2 ranges. The exponential factors were in the range of 4.24 to 6.31. The experimental and calculated Mw's were in a good agreement.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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