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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 163-173 
    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: ABA-type block polymers of styrene (monomer A) and isoprene or butadiene were prepared using two commercially available dilithium adducts of isoprene as initiators. One (DiLi-1) was predominantly dilithio diisoprene and contained a small amount of dimethyl ether (ether/Li 〉 1.0). The second (DiLi-1 C.E.) was a higher molecular weight version of DiLi-1, containing about seven isoprene units per molecule. It contained only a trace of dimethyl ether (ether/Li 〈 0.1). Polymers were made by charging all of the monomers at the start of the reaction. The diene polymerized first, incorporating some styrene. When the diene was consumed, the difunctional polymer chains then added a block of nearly pure polystyrene at each end. Thus an ABA-type polymer was synthesized in one step. These polymers show the usual behavior of pseudo-vulcanized elastomers. Their stress-strain curves are given. The SBS polymers had the higher tensile strengths. None had tensile strengths as high as SBS or SIS polymers made with n- or sec-butyllithium. It was shown that the diene blocks contain appreciable amounts of styrene. This leads to more compatibility between the A and B blocks; it also shortens the styrene blocks compared to the theoretical lengths of “pure” blocks. Both effects can lead to loss of tensile strength. Microstructures of the diene homopolymers made with these initiators are also given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 747-756 
    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: The isothermal decomposition of a phenolic resin in a phenolic-carbon cloth composite was measured at approximately 0.1 to 0.2 torr over the temperature range of 105°-718°C. The kinetics are initially first order and, in the later stages, second order. An analytic technique is provided for calculating the maximum quantity of resin which will volatilize during decomposition, thereby obviating the necessity of measurements for extended time periods. The amount of resin available for volatilization during decomposition varies with temperature and is in equilibrium with resin, which does not volatilize. Plots of the equilibrium constant versus the reciprocal absolute temperature show that two equilibria are involved: one which predominates up to 352°C and the other above this temperature. The heats of reaction are 2.2 and 15.3 kcal/mole. The first value is associated with hydrogen bonding and the second with decomposition and oxidation activation energies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 91-103 
    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: The isothermal decomposition of a phenolic resin in a phenolic-carbon cloth composite was measured in air at 0.1 to 0.2 torr over the temperature range 104-718°C. Two decomposition rate relationships are presented that can be used to predict decomposition. One assumes two second-order consecutive rate-controlling reactions, and the other assumes a diffusion-limited second-order reaction. Two rate constants govern each relationship, one being operative during the initial decomposition stages, and the other during the final stages. Evidence is presented to support the applicability of both relationships to predict decomposition over the entire temperature range studied. Arrhenius plots of the rate constants consist of several segments linearly connected. Activation energies and frequency factors computed from these segments cover a broad range of values. The activation energies are used to correlate the temperature ranges with the predominant products formed in these ranges.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 4 (1970), S. 41-53 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of several 4,5-disubstituted-2-oxazolidones and several related N-methyl derivatives have been determined. Fragmentation has been found to be a function of three factors: (1) the size of the alkyl function at C-5, (2) the location of the aryl substituent, and (3) replacement of N—H by N—CH3. In particular, aryl or bulky alkyl groups substituted at C-5 result in protonated aldehyde derived from hydrogen rearrangement from nitrogen. With other substituents, the most intense ions are nitrogen containing fragments. In the latter case the fragmentation pathway has been elucidated with the aid of metastable peaks observed using defocusing techniques.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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