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  • Polymer and Materials Science  (6)
  • 2020-2024
  • 1955-1959  (6)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 31 (1958), S. 481-497 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acrylamide was polymerized in aqueous solution with chlorate-sulfite initiator under the following conditions: temperature, 15-75°C.; pH, 1.5-3.9; monomer concentration, 0.3-1.1 mole/liter; NaClO3 concentration, 0.26-2.1 × 10-4 mole/liter; and Na2-SO3 concentration, 0.79-6.3 × 10-4 mole/liter. The weight-average molecular weight of the polymers formed under these conditions is in the range of 1-3 × 106. It was found that up to 40-50% conversion, the following rate equation holds: \documentclass{article}\pagestyle{empty}\begin{document}$ R_p = - \frac{{d[{\rm M}]}}{{dt}} = K\frac{{\left( {\left[ {\rm C} \right]{\rm O}_3^ - \left[ {{\rm H}_2 {\rm SO}_3 } \right]} \right)^{1/2} }}{{[{\rm M}]_0^{3/2} }}[{\rm M}]^{3/2} $\end{document} where Rp is the overall rate of polymerization, [M] the instantaneous monomer concentration at time t, and [M]0 the initial monomer concentration. At 50°C., K = 6.9 ± 0.9 l. mole-1 sec.-1 Activation energy within the temperature range studied was found to be 7.3 kcal./mole. The value of k2p/kt at 50°C. was estimated to be about 30 l. mole-1 sec.-1 The rate dependence on [M]5/2[M]-3/20 is explained by assuming that the polymer formed binds part of the remaining monomer. The presence of ferrous ions in the polymerization system increases the rate but decreases the molecular weight of the polymer formed. Up to 3.6 × 10-3 mole/l. of [Fe++], the rate is affected in such a manner that \documentclass{article}\pagestyle{empty}\begin{document}$ K = 6.9 + 29{\rm }[{\rm Fe}^{ + + } ]^{0.3} $\end{document} Chromic ions tend to retard and nickel ions tend to accelerate the rate of polymerization. It was found that HSO3- is an effective chain transfer agent. Its chain transfer constant was estimated to be about 0.17.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chemical and physical properties of polychloroprenes made at temperatures ranging from -60 to +200°C. are discussed in the light of knowledge of structure gained from analysis of their crystallization behavior and infrared absorption spectra. The properties of polychloroprenes made below 0°C. are shown to be dominated by the preponderance of trans-2-chloro-2-butenylene units in their structure, e.g., they are highly crystalline and relatively unreactive. Polychloroprenes made at 10-90°C. show typical elastomeric properties and the chemical reactivity expected from the presence of a higher proportion of the allylic chloride units that result from 1,2-polymerization. Polychloroprenes made at temperatures over 100°C. contain an even higher proportion of 1,2-units and hence are unstable chemically. They are generally obtained as crosslinked gels. Chloroprene polymers made by ionic initiation are found to be chemically unstable, low molecular gums or resins. Their structure remains to be elucidated.
    Additional Material: 5 Tab.
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  • 3
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Vinyl acetate emulsion polymerization at 70°C. using potassium peroxydisulfate as initiator and a partially hydrolyzed polyvinyl acetate as emulsifying agent has been studied. In agreement with the Smith and Ewart scheme for emulsion polymerizations, the polymerization rate was found to be independent of the total monomer amount present and approximately dependent on the 3/5 power of the emulsifier concentration. Instead of a 2/5 power dependence on initiator concentration for the rate of polymerization, a 0.7 power dependence was found. From surface tension measurements an “apparent critical micelle concentration” was determined for aqueous solutions of the emulsifier. However, light scattering studies gave no indication that aggregates of the emulsifier exist in aqueous solutions.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 36 (1959), S. 564-565 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 25 (1957), S. 483-485 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 41 (1959), S. 225-230 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The study of the autocondensation of thiodiglycol initiated in Part I has been extended under conditions likely to give water-insoluble polymers of higher molecular weight. The catalytic power of 27 compounds was first determined, and the rates of polymer production were assessed for reaction in the presence of those eleven compounds thus found to be most effective. On the basis of mean molecular weight (3300), solubility in benzene, yield, and appearance of the product, phosphorus pentoxide was chosen for more exhaustive tests. Heating thiodiglycol with P2O5 (2.0%) for 12 hr. at 140°/760 mm., followed by heating for increasing periods at 150°/40 mm., yielded products ranging from a viscous liquid (M.W. 2500; ηsp 0.067) to a rubbery dark-brown wax (M.W. 6500; ηsp 1.061). The solubility in benzene, chloroform, and dichlorodiethyl ether decreased with increasing molecular weight. The catalyst tended to become exhausted: this was found to be due to chemical combination. 2,2′-Dihydroxydiethyl disulfide was successfully autocondensed under similar conditions to give an elastic, insoluble polymer with some tendency to cold flow, presumably built up from C2H4OC2H4S2 units.
    Additional Material: 2 Ill.
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