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  • Polymer and Materials Science  (46)
  • 2020-2024
  • 1990-1994  (37)
  • 1975-1979  (8)
  • 1970-1974  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Polymer precursor synthesis of alumina fibers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 495-503 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High strength alumina fibers were fabricated with a polymer precursor process which was monitored with 13C-NMR, elemental analysis, gas evolution, SEM, and X-ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i-propanoyl groups in molar ratios of 0.2 : 0.8 to 0.4 : 0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320-350°C, and then calcined at 950°C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290406
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  • 2
    Electronic Resource
    Electronic Resource
    Stereoselective nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate in cyclohexanone solution: Influence of the reaction temperature on the mechanism (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 99-104 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300112
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical approach to cationic polymerization of alkenylfurans. II. Ab initio and semiempirical study of relevant steps in the reaction mechanism (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2497-2502 
    Details
    ISSN: 0887-624X
    Keywords: ab initio ; AM1 ; cationic polymerization ; reaction mechanism ; furans ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: SCF ab initio and AM1 semiempirical calculations with full geometry optimization have been carried out to model the initial steps of alkenylfuran cationic polymerization. Semiempirical procedures have been used to model propagation steps. Proton affinities of the relevant neutral species as well as the heats of formation of probable dimers were calculated. The results allow the explanation of the experimental behavior. The capabilities of the employed methods to describe these type of processes is discussed. It is confirmed that competition between vinyl and ring site attacks is the most important feature in these systems. © 1992 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301203
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of the chemical modification of phenoxy resin on its miscibility with poly(2-vinyl pyridine)Presented in part at a conference on Polymer Spectroscopy Grasmere, UK, 28 March-1 April 1993. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 393-398 
    Details
    ISSN: 0959-8103
    Keywords: phenoxy resin ; poly(2-vinyl pyridine) ; miscibility ; FTIR ; DSC ; 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 influence of the chemical modification of the hydroxyl groups of phenoxy resin (PH) by benzoate, acetate and methoxy groups on its miscibility with poly(2-vinyl pyridine) (P2VPy) is investigated. Both DSC and FTIR results permit the definition of three distinctive regions: up to 40% modification all 50/50 blends are miscible; between 40 and 55% modification all blends present partial miscibility and at higher than 55% modification the blends are totally immiscible. Specific interactions between the hydroxyl groups of PH and the amine groups of P2VPy are put forward as an explanation for these observations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210330409
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental and theoretical aspects of electrical characteristics of Au/ZnSe/GaAs heterostructures (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 81-88 
    Details
    ISSN: 1057-9257
    Keywords: Semiconductor heterojunctions ; Admittance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We present results of a theoretical and experimental study of Au—ZnSe—GaAs heterostructures. In the theoretical part we report the band diagrams, charge densities and static I-V curves obtained from a detailed numerical analysis. In the experimental part we give the results for the static I-V curves and frequency-dependent admittance and impedance at different bias voltages for an Au—ZnSe—GaAs heterostructure with a ZnSe layer of 2.75 μm thickness. An explicit analysis of the data shows that the system can be represented by an equivalent circuit of two RC elements in series corresponding to the ZnSe—GaAs and Au—Se heterojunctions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860030112
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  • 6
    Electronic Resource
    Electronic Resource
    Phase behavior and mechanical properties of injection molded poly(ethylene terephthalate)/polyarylate blends (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1135-1143 
    Details
    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: Directly injection molded blends, composed of poly(ethylene terephthalate) and a polyarylate of bisphenol A, and isophthalic/terephthalic acids have been studied. Both their phase behavior and their mechanical properties after this blending method have been determined. After injection molding, the poly(ethylene terephthalate)/polyarylate blends show a single glass transition by differential scanning calorimetry, although the transition peaks of the blends widen when observed by dynamic mechanical analysis. The calorimetric results show a hindered crystallization of poly(ethylene terephthalate), due to the presence of polyarylate and the occurrence of interchange reactions. The mechanical behavior observed shows an improvement in the small-strain properties of the blends with respect to those of the pure components. The break and impact properties of the blends show negative deviations with respect to linearity. These deviations are less important when high polyarylate content exists in the blends.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450702
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  • 7
    Electronic Resource
    Electronic Resource
    Miscibility of poly(ether imide) and poly(ethylene terephthalate) (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 935-937 
    Details
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070480518
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  • 8
    Electronic Resource
    Electronic Resource
    Studies on enzymatic resistance and molecular structure by 13C-NMR of cellulosic ethers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 347-352 
    Details
    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: A viscometric method to evaluate the enzymatic resistance of cellulosic ethers is proposed. The method was applied to samples of hydroxyethylcellulose (HEC) with molar substitution between 1.8 and 2.5. The results are discussed in terms of the values of Degree of Substitution and the average unsubstituted primary hydroxyl groups, obtained by high-resolution 13C-NMR of the neat polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440218
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  • 9
    Electronic Resource
    Electronic Resource
    Physical and mechanical properties of henequen fibers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 749-756 
    Details
    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: A study of morphology, physical, and mechanical properties of henequen (Agave fourcroydes) fibers have been performed in this article. It has been concluded that properties of the fibers are more uniform in their middle section. As other natural hard fibers, henequen has a relative high tenacity, low elongation at break and a low modulus. These properties suggest that the fiber could be used as reinforcing agent in composite materials.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430412
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  • 10
    Electronic Resource
    Electronic Resource
    Poly(ethylene terephthalate)/polyarylate blends: Mixing and interchange reactions in injection molding (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 223-230 
    Details
    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: Blends composed of poly(ethylene terephthalate) and a polyarylate have been melt-mixed and molded in a reciprocating screw injection-molding machine for different plasticization times. Interchange reactions between the blend components occur during processing and at a greater level as the plasticization time increases. These reactions led to a progressive homogenization of the blends as well as to a hindered crystallization of PET. The effect of the plasticization time on the mechanical properties of the blends seems to be a consequence of interchange reactions as well as of the degradation of the blends at the highest plasticization times. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510203
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