Strong and stable bonding of rubber to brass-coated metal cord is one of the most important conditions determining the service life of a tyre. The most effective method for improving adhesion in the rubber-brass system is to introduce special ingredients, so-called adhesion promoters, into the rubber. The main types of adhesion promoter used in practice are systems based on organic salts of variable-valency metals, primarily cobalt. Their use, however, has certain negative effects: with amounts of promoters in the rubber mix of over 0.1 % - 0.3 % (in terms of metal atoms), the catalytic oxidation of the elastomer matrix is accelerated, the scorching tendency of rubber mixes increases, and degradation of the vulcanisation bonds occurs. Furthermore, in the formulation of the rubber compounds it is necessary to use increased amounts of sulfur, which leads to a reduction in the heat resistance of the vulcanisates. The shortcomings pointed out can be compensated for partially by correct selection of the organic ligand of the promoter and by its combined use with stabilising, modifying, and activating additives and other special rubber mix ingredients. Here, the effect of coprecipitated Ca/Co and Ca/Ni hydrosilicates on the adhesion of coating rubbers to brass-coated metal cord was investigated. Hydrosilicates were advantageous compared to silica filler because of the lower interaction with thiokol due to less surface hydroxyl groups. The more effective consumption of thiokol in hydrosilicate systems is confirmed by higher adhesion stability. The action of combined promoters can be divided into two parts. On the one hand, the sulphur in the thiokol, capable of being activated during vulcanisation, takes part in the formation of an optimum adhesive joint between rubber and brass. On the other hand, insoluble hydrosilicates are capable of detaching Co(2+) (or Ni2+) ions during ageing under the action of moisture, ensuring protection of the surface of the cord against corrosion in aggressive media. Thus, the combined use of cobalt (or nickel) hydrosilicates with thiokol makes it possible to produce effective promoting systems with a reduced content of variable-valency metals, shown by physico-mechanical and adhesion properties of breaker rubbers.


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    Title :

    Use of cobalt and nickel hydrosilicates for improving adhesion between rubber and brass-coated metal cord


    Contributors:


    Publication date :

    2007


    Size :

    5 Seiten, 1 Bild, 3 Tabellen, 25 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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