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  • Polymer and Materials Science  (14)
  • Protoplast fusion  (2)
  • 05.60  (1)
  • 11
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2773-2784 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study embodies the results and discussion of a comprehensive and systematic investigation of the mechanism of sulfuration of styrene-butadiene rubber accelerated by N-cyclohexylbenzothiazole-2-sulfenamide (CBS) with and without activators. Dicumyl peroxide (DCP) has been taken as a chemical aid to distinguish between free-radical and polar mechanisms of sulfuration. The rate constant for DCP decomposition in presence of CBS and the reduction in crosslink density by CBS have also been studied. With a constant amount of DCP and sulfur the crosslink density increases with increasing CBS concentration. In the presence of ZnO and stearic acid, crosslinking proceeds faster than in a similar system without these ingredients, and with DCP the crosslinks are found to be formed nearly additively as confirmed by methyl iodide treatment of the vulcanizates. In the absence of DCP, the crosslinking is characterized by an induction period, even in presence of ZnO and stearic acid. In the presence of sulfur, the 2-mercaptobenzothiazole (MSH) or amine or amine salt form crosslinkins by ionic reaction.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2971-2983 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diphenylguanidine (DPG) raises the rate of decomposition of dicumylperoxide (DCP) and the crosslinking maxima due to DCP is lowered to some extent by DPG. When the molar proportion of DPG-S is approximately 1:1, no additive results of crosslink formation (as reported for NR) are observed. Zinc oxide and stearic acid increase the rate of crosslinking as well as the crosslinking maxima. In the present study it appears most probable that DPG-accelerated sulfuration of SBR is an ionic process. At a constant level of DCP and sulfur crosslink density increases when the amount of DPG is increased; a constant level of DCP and DPG crosslinking increases with rising sulfur concentration.An increase in the concentration of DPG or sulfur leads to greater formation of the complex as well as a change in its composition. The effect of DPG is more pronounced, for by reducing the number of sulfur atoms more sulfur is available for crosslinking. Sulfur absorbs little SO2 or H2S; if it is already saturated, there is no perceptible effect. DPG does absorb H2S or SO2 and the rate and maxima of crosslinks is increased. The effect of SO2 is higher because of the higher Ka values of H2SO3 and consequently higher concentration of HSO3-. Reversion is a free-radical process inhibited by free DPG present in the system. In the presence of zinc oxide and stearic acid the reaction follows a polar mechanism as well as a radical mechanism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 37 (1959), S. 469-483 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Vinyl benzoate was polymerized in bulk as well as in solution, using benzoyl peroxide and azobisisobutyronitrile initiator at a temperature of 79.6°C. The overall rate of polymerization was found to be proportional to the concentration of the monomer and to the square root of the initiator concentration. Polymerization progressed to a normal extent, except that it increased with conversion, probably because of transfer with polymer. The value of the transfer constants with the monomer, initiator, and some solvents are reported.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 97 (1966), S. 174-188 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In der vorliegenden Abhandlung wird über die Abhängigkeit der Beschleunigung der Vulkanisation von gebleichtem Krepp (Naturgummi) und von nichtpigmentiertem Styrol-Butadien-Gummi von der Konzentration an 2-Mercapto-benzthiazol (MTB) als Beschleuniger berichtet. Es wurde gefunden, daß die Menge der Abnahme an freiem Schwefel und die Zunahme der Vernetzungsdichte annähernd proportional der 0,8 ten bzw. 0,9ten Potenz der Konzentration des Beschleunigers sind. Es wurde weiter gefunden, daß die Abnahme an freiem 2-Mercapto-benzthiazol (MBT) dem Gesetz der ersten Reaktionsordnung gehorcht und daß sich bereits während des Zusammenmischens ungefähr 6-10% des MBT mit dem Gummi verbinden. Die optimalen Vulkanisationszeiten, die nach verschiedenen Methoden erhalten wurden (aus dem Abfallen der Menge des freien Schwefels, der Zunahme der Vernetzungsdichte, der Zugfestigkeit und Messungen des Moduls), stimmen annähernd überein.
    Notes: The dependence of the rate of accelerated vulcanization of pale crepe and non-pigmented styrene-butadiene rubber on the concentration of 2-mercaptobenzothiazole (MBT) accelerator has been reported in this paper. The rate of decrease of free sulfur and increase of cross-linking density have been found to be approximately proportional to the (concentration of accelerator)n where n is 0.8 and 0.9. The decrease of free MBT is found to follow a first order reaction with respect to time of cure and about 6-10% of MBT is found to combine with rubber during mixing. The optimum times of cure as obtained from decrease of free sulphur, increase of cross-linking density, tensile strength, and modulus plots against time of cure fall within agreeable range.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 35 (1959), S. 292-295 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 109 (1967), S. 217-230 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Vernetzerwirksamkeit von Dicumylperoxid bei Styrol-Butadiengummi (SBR-1507) wurde mit Hilfe von Quellungsmessungen erfaßt. Die erhaltenen Werte sind 2,5 bzw. 5 für ungereinigten bzw. gereinigten SBR. Der niedrigere Wert im ersten Fall wurde der Vernichtung von Peroxyradikalen durch Antioxydantien im Gummi zugeschrieben. Die physikalischen Vernetzungen, die beim gereinigten SBR auf Kettenverknäuelungen zurückzuführen sind, betragen 0,14.10-4 Mol/g Gummi (oder 0,07.10-4 Vernetzungsstellen der Kettenverknäuelungen/g Gummi). Die Löslichkeitsparameter für gereinigten SBR aus Quellungs- und Viskositätsmessungen betragen 8.45 (kcal/ml)1/2 bzw. als Kohäsionsenergiedichte 71,403 kcal/ml. Mit diesem Wert des Löslichkeitsparameters wird der Lösungsmittel-Polymer-Wechselwirkungsparameter berechnet und durch die Methode von HUMMEL bestätigt. Der Durchschnittswert beträgt 0,37.
    Notes: The cross-linking efficiency of dicumyl peroxide with styrene-butadiene rubber (SBR-1507) has been measured by the swelling method. The values are found to be 2.5 and 5.0 for unpurified and purified SBR, respectively. The lower value in the former case has been ascribed to the destruction of peroxy radicals by the antioxidants present in the rubber. The physical cross-links due to chain entanglement for purified SBR are found to be 0.14 . 10-4 mole/g of rubber (0-07.10-4 cross-links due to chain entanglement/g of rubber). The solubility parameter for purified SBR as determined from both swelling and viscosity measurements is found to be 8.45 (kcal/ml)1/2 or cohesive energy density as 71.403 kcal/ml. Using this value of the solubility parameter, the solvent-polymer interaction parameter is calculated and is further verified by HUMMEL'S method. The average value is found to be 0.37.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 21 (1983), S. 263-270 
    ISSN: 0360-6384
    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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