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  • 11
    Digitale Medien
    Digitale Medien
    High-energy ion implantation of polymers: Poly(ethylene terephthalate) (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 817-827 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of high-energy ion implantation of oxygen into a thin film of poly(ethylene terephthalate) (PET) was studied by Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC). Mylar samples 13 μm thick were implanted with 6-MeV oxygen ions at fluences ranging from 5 × 1012 to 2 × 1014 ions/cm2. The DSC data showed a substantial loss of crystallinity, even at the lowest fluence, which extended deeper into the polymer film than the predicted range for oxygen deceleration in PET. Solubility measurements indicated the presence of cross-linking, especially at the highest fluence, but bands due to cross-linking could not be detected in the infrared. The trans/gauche ratio for the glycol group conformation was measured by a pair of conformationally sensitive infrared bands. Surprisingly, the conformation of the glycol segments did not change appreciably with increasing fluence, although crystallinity decreased and degree of cross-linking increased. The implications these results have on possible mechanisms of chemical and physical alterations of the polymer structure by ion implantation are discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1987.090250410
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  • 12
    Digitale Medien
    Digitale Medien
    “Living radical” polymerization of styrene in the presence of a nitroxide compound (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 683-691 
    Details
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The influence of parameters such as styrene dilution and active site concentration on the polymerization of styrene in the presence of a di-tert-butyl nitroxide adduct (A-T) was examined. It is confirmed that the rate of styrene polymerization is independent of A-T concentration, with no monomer dilution effect. An increase in radical concentration generated in the medium leads to faster propagation, but the molecular weight of the polymers formed is alway controlled by the A-T concentration.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/marc.1996.030171003
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  • 13
    Digitale Medien
    Digitale Medien
    Bismaléimides et polybismaléimides à pont éther et thioéther - synthèse, réactivité et tenue thermique (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 3837-3849 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This paper describes the synthesis and characterization of six structurally different bismaleimides. They were prepared by reacting maleic anhydride with diamines containing ether and thioether bridges. Thermal polymerization of these monomers in the presence or absence of radical initiators was investigated by differential scanning calorimetry. Activation energy (E), kinetic order (n), rate constants (k) and heat of polymerization (ΔH) were determined. The cured resins are stable up to 334-418°C both in argon and air atmosphere.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1996.021971127
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  • 14
    Digitale Medien
    Digitale Medien
    High-energy ion implantation of polymers: Poly(vinylidene fluoride) (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1457-1467 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(vinylidene fluoride) films were implanted with high-energy (up to 6 MeV) He, C, O, and Ni ions and characterized using DSC, FTIR, and solubility measurements. None of the ions were energetic enough to penetrate the polymer film completely. The effects of ion energy, fluence, and ion type were studied individually. The implantation process lowered the crystallinity, induced crosslinking, and produced carbonyl groups on the polymer. The ion energy (in the range 0.4-4.5 MeV for He ions) had the most drastic effect, the radiation damage was found to increase with decreasing energy. The sample implanted with 0.4 MeV He ions lost 81% of its initial crystallinity and was only 24% soluble, even though the incident ions have a range of only 2.7 μm in this case. The other samples retained most of their initial crystallinity but still were substantially cross-linked. The results can be qualitatively explained by assuming that hydrogen free radicals, produced during implantation, can diffuse throughout the sample and react, resulting in crystallinity and solubility losses beyond the ion deceleration region.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1988.090260709
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  • 15
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of an amphoteric ion-exchange membrane (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 705-713 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An amphoteric ion-exchange membrane was prepared by chemical grafting of acrylic acid and dimethyl amino-2-ethyl methacrylate on ozonized polyethylene. The effects of the variation of external pH on the physicochemical properties of this membrane were studied (exchange capacity, electrical resistance, water and electrolyte content, and membrane potential). The determination of the mean activity coefficient of the NaCl in the membrane phase using the Donnan equilibrium equation reveals that this coefficient increases with the NaCl concentration in the external solution. Fundamental electrochemical properties of the amphoteric membrane are discussed on the basis of the variation of the membrane selectivity with the external electrolyte concentrations and the pH. The properties at neutral pH are accounted for by a mutual neutralization of some acidic and basic groups in the membrane phase.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1991.090290609
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  • 16
    Digitale Medien
    Digitale Medien
    Electrical degradation of polypropylene: A study by FTIR microspectroscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1121-1124 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1992.070460623
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  • 17
    Digitale Medien
    Digitale Medien
    A reinvestigation of electrolyte effects in the emulsion polymerisation of styrene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 379-387 
    Details
    ISSN: 0959-8103
    Schlagwort(e): electrolyte ; latex ; particle size ; rate of polymerisation ; polydispersity ; adsorption ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effects of adding potassium chloride in concentrations below that required to coagulate the latex to recips of emulsion polymerisation of styrene have been investigated using different concentrations of potassium octadecanoate, which has a low critical micelle concentration (CMC), and potassium dodecanoate, which has a moderately high CMC. At relatively high concentration of octadecanoate the final particle size is significantly increased; the rate of polymerisation is initially increased but later retarded. The effects of increasing micelle size and increased rate of coalescence are dominant. At lower concentration of this emulsifier, the rate is reduced from the onset of interval II.With dodecanoate, concentrations of electrolyte up to 0.3 M accelerate the rate. No significant change in the particle size was observed up to 0.2M electrolyte, thereafter it slightly increased. The increase in micellar concentration can only partially account for these effects. It is believed that the increase in the amount of solubilised monomer inside the micelles, and later inside the latex particles, and the resistance to coalescence (because of the favourable adsorption mechanism of this emulsifier) may account for these observations.With both emulsifiers, electrolyte reduces the induction period and latices with narrow particle size distributions are produced.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1994.210350411
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  • 18
    Digitale Medien
    Digitale Medien
    Saturation swelling and the seeded emulsion polymerisation of styrene at high ionic strength (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 40 (1996), S. 307-313 
    Details
    ISSN: 0959-8103
    Schlagwort(e): swelling ; seed ; electrolyte ; particle size ; rate of polymerisation ; coalescence ; styrene ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effects of adding inorganic electrolyte (below the critical coagulation concentration) have been investigated in two systems for the emulsion polymerisation of styrene. In one system, potassium chloride, at different concentrations, was added at the end of interval I, using three different ionic emulsifiers: potassium octadecanoate which has a low critical micelle concentration (CMC), potassium dodecanoate and sodium dodecyl sulphate (SDS), which have moderately high CMC. A significant increase in the rate of polymerisation was observed in all cases even at the higher levels of electrolyte at which the rate is reduced if the electrolyte is added from the onset of polymerisation. In the second system, the effects of adding sodium chloride, in concentrations up to 0.2M, on the seeded emulsion polymerisation of styrene have been followed. A significant increase in the rate was observed as electrolyte level was increased, with no significant change in particle size. Saturation swelling measurements indicated a slight increase in monomer concentration inside the particles as electrolyte concentration was increased. Evaluation of the average number of free radicals per particle, n¯, by a steady state approach indicates an increase in the value of n¯ as electrolyte level is increased. The value of n¯ is below 0.5 but approaches this value at the highest electrolyte concentration. The increased surface area of the particles may account for this effect by increasing the capture efficiency of the radicals by the particles.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Residual porosity in polymeric latex films (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 557-569 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Solubility and diffusivity measurements of a probe gas (CO2), which has an inherently low solubility in the polymer, have been used to characterize residual porosity in polymeric latex films. Sorption isotherms resembling those of a glassy polymer were obtained, even though the glass transition temperature of the polymer was 1°C, about 30°C below the experimental temperature. Solvent cast films of the same polymer exhibited much lower solubilities, and followed the expected Henry's law behavior. CO2 solubility and diffusivity were found to decrease with aging time for the latex films, but did not quite reach the values of the solvent cast films, even after 75 days at room temperature. The sorption data could be described by the dual-mode sorption model, which is commonly employed in the analysis of glassy polymer sorption isotherms. Estimates of the amount of porosity were made from the sorption data, and values ranging from 0.6-0.03% were obtained for latex films aged from 62 h to 75 days, respectively. Our results suggest that permeability differences noted by others for latex and solvent cast films of the same polymer are due to the substantial solubility differences for low-solubility penetrants in these two types of films.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1989.070380315
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  • 20
    Digitale Medien
    Digitale Medien
    Colorimetric evaluation of thermooxidative degradation of nylon 6 fibers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 265-270 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Nylon 6 fibers were annealed in air at 160°C for periods ranging from 1 to 10 h. Their spectral reflectance values were measured. Color parameters, including luminance factor, dominant wavelength, purity, and the color difference between annealed nylon 6 fiber samples and unheated ones were calculated. The observed variations in the colors of samples were assumed due to the thermal and oxidation degradations. The behavior of the color parameters with heating duration was compared with the general kinetic curve of thermooxidative degradation of polymers and the match between them is discussed. The color difference ΔE values is recommended for monitoring the thermooxidative degradation of nylon 6 fibers. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1995.070570303
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