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  • 1
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of organic solvents on the rate of heterogeneous aqueous polymerization initiated by the K2S2O8—Na2S2O4 redox pair has been studied. The separating polymer phase remains in colloidal dispersion, the stability of which is partly due to charge and partly due to hydration. Both the water-miscible and water-immiscible organic liquids decrease the rate of polymerization, the limiting conversion, and the molecular weight of the polymers. It has been suggested that the water-miscible organic liquids preferentially solvate the latex particles and thereby decrease the hydration stability and monomer concentration in the latex particles, whereas the water-immiscible organic liquids decrease the monomer concentration in the latex particles due to the partition of the monomer between the aqueous and the nonaqueous phases. Thus the fall in the rate and molecular weight of the polymers may be ascribed to the increase in the termination rate by the faster coagulation of the latex particles and dilution of monomer concentration at the reaction site.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of N-vinylcarbazole has been carried out at 60°C under nitrogen with different grades of carbon black, N220, N110, N330, and N660 as heterogeneous catalysts. The order of efficiency of the catalysts in regard to the polymerization is: N220 〉 N110 〉 N660 〉 N330. Effect of solvent polarity on the polymerization has been studied with acetonitrile, 1,2-dichloroethane, and toluene-nitrobenzene mixtures. Nitrobenzene, with highest polarity, affords the highest rate, which decreases with decreasing nitrobenzene percentage in the solvent mixture. These features suggest the polymerization to be cationic in nature. The relative viscosities of the polymers are low, but tend to increase only slightly with increasing nitrobenzene content. The rate of polymerization can be expressed by the relation \documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{{\rm d}\left[ {\rm M} \right]}}{{{\rm dt}}} = k_1 [{\rm M}]{\rm [Carbon Black]} $$\end{document} A suitable kinetic model has been presented in conformity with the experimental findings.
    Additional Material: 3 Ill.
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  • 5
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A few redox systems containing thiourea as reductant have been found to be quite effective in initiating vinyl polymerization in aqueous media and polymers obtained in the process have all been found to contain amino endgroups to various extents by the application of dye techniques. Quite a few oxidants have so far been utilized for this purpose; among them are ferric chloride (Fe3+), ethylene dibiguanide complex salts of tripositive silver (Ag3+), hydrogen peroxide (H2O2), persulfate (S2O82-), bromate (BrO3-) + hydrochloric acid (HCl). In case of oxidants Fe3+ and Ag3+, amino endgroups are mainly incorporated in polymers; but in case of oxidants H2O2 and S2O82-, fragments of oxidants are also incorporated as hydroxyl and sulfate endgroups. BrO3-, however, forms a very efficient redox-initiating system with thiourea, as is evidenced by its capability of polymerizing even hydroquinone-stabilized water-soluble vinyl monomers at very low temperature (∼0°C.) and at a quite rapid rate. Besides amino endgroups, sulfonate endgroups have also been detected in polymers in this case, and the relative extents of these two types of endgroups depend generally on the acid concentration of the system. Evidences so far collected indicate the generation of S—C(=NH)NH2 radicals in the system by oxidation of isothiourea, HS—C(=NH)NH2, and these are incorporated in polymers as endgroups. Sulfonate endgroups may be generated by oxidation of these amino-bearing endgroups. Suitable initiation mechanisms have been suggested in each case.
    Additional Material: 5 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 15 (1996), S. 165-170 
    ISSN: 0730-6679
    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
    Notes: The Institut für Kunststoffverarbeitung in Aachen, Germany is undertaking investigations in a simulation program of the process of forming fabric-reinforced thermoplastics, in order to attain an efficient instrument for the layout of components as early as in the desing stage. The current state of the investigations provides instruments for the determination of several data crucial for industrial applications. These are fiber placement and wall thickness distribution after forming, displacement paths required, interlaminar sliding, minimum blank size required, as well as the heat transfer during forming. Current and future investigations will enhance the program's range of performance. Of particular interest are calculation of three-dimensional anisotropic temperature distribution, of the mechanical characteristic values, as well as of shrinkage and warpage behaviors. As these investigations are concluded, the designer will have a comprehensive computer-assisted engineering system at hand for the layout and dimensioning of components made of fiber-reinforced thermoplastics produced in a forming process. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 7
    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: N-vinyl-Carbazole (NVC) has been polymerized in the presence of pyrrole (PY) by anhydrous ferric chloride. The copolymer has been characterized by IR Spectroscopy. Thermal stability of P(PY-NVC) is intermediate between that of PNVC and PPY, respectively. DSC reveals a single glass transition break at 180-200°C for P(PY-NVC), which is higher than the Tg for polypyrrole (∼ 165°C), but is lower than that for PNVC (∼ 227°C). The XRD analysis reveals PPY to be totally amorphous and shows the percent crystallinity for P(PY-NVC) to be less than that of PNVC. Dielectric constants of the polymers follow the trend: PPY 〉 P(PY-NVC) 〉 PNVC, and fall sharply with the applied frequency to a limiting value. The polymers are characterized by a broad dielectric relaxation. DC conductivity is dependent on temperature and FeCl3/polymer mole ratio and at a particular temperature follows the trend: PPY 〉 P(PY-NVC) 〉 PNVC. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 8
    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: Polystyrene-divinylbenzene (PS-DVB) (partially chloromethylated) has been modified by anchoring dipyridylamine (DPA) followed by subsequent complexation with Fe(III), Co(II), and Cu(II). Analytical and spectroscopic evidence has been presented to confirm the attachment of the metal-dipyridyl complex on the PS-DVB matrix. All the metal-loaded polymers exhibit appreciable improvement in thermal stability relative to the base polymer, the initial decomposition temperature and stability order being PS-DVB-DPA-Cu(315°C) 〉 PS-DVB-DPA-Fe(II) (310°C) 〉 PS-DVB-DPA-Co (300°C) 〉 PS-DVB-DPA (280°C) = PS-DVB.DTA studies reveal exothermic peaks between 300 and 380°C, 420 and 440°C, and 500 and 700°C, which are ascribable to the exothermic cleavage of the PS-DVB-DPA matrix. The glass transition temperatures of the modified polymers do not reveal any characteristic difference from the corresponding value for the base polymer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 9
    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: Bis(diisopropyl)thiophosphoryl disfulfide (DIPDIS) can be successfully used to form a blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar NR through a chemical link between the two. It is revealed from the study that the physical properties of the vulcanizates obtained from the NR-XNBR blend could be significantly improved by the judicious selection of the NR:XNBR ratio. These properties can further be improved by two-stage vulcanization as described in the procedure. The SEM study reveals that it is possible to form a coherent blend of NR and XNBR in the presence of DIPDIS. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 10
    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: Trimellitic anhydride and pyromellitic dianhydride have been polycondensed with Cu(II)-phenanthroline complex as a comonomer in the presence of anhydrous ZnCl2 under selective conditions. Elemental diffuse reflectance and infrared spectroscopic and X-ray diffraction (XRD) analysis data of these polymers have been correlated with the tentative structure Proposed for these polycondensates. Thermal stability and dielectric and conductivity characteristics of these polycondensates have been evaluated to understand the effect of the ligand and the anhydride moieties on these properties. Unlike the polymer-anchored 3d-metal complexes, these polycondensates fail to initiate the cationic polymerization of N-vinylcarbazole. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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