Brass adhesion compounding

Rubber tyre cord adhesion W J VAN OOlJ Adhesion to brass-coated steel Rubber-based adhesives J M MARTfN MARTInEZ General introduction Rubber-based adhesives compounding J M MARTIN MARTfNEZ Formulations, etc. 

Resorcinol formaldehyde resin is a vital ingredient in the HRH rubber adhesion compounds (such as wire coat stock or breaker stock) in order to achieve good rubber-to-brass-coated steel tire cord adhesion. 

Rubber Compound Effects. Buchan " reviewed natural as well as synthetic rubber compounds and their adhesion to brass. However, compound studies are to some extent largely empirical because of the complexity of the different compound systems used in the rubber industry today. One can, however, draw several conclusions from the many adhesion studies made to date. 

Tire Cord. Melamine resins are also used to improve the adhesion of mbber to reinforcing cord in tires. Textile cord is normally coated with a latex dip solution composed of a vinylpyridine—styrene—butadiene latex mbber containing resorcinol—formaldehyde resin.. The dip coat is cured prior to use. The dip coat improves the adhesion of the textile cord to mbber. Further improvement in adhesion is provided by adding resorcinol and hexa(methoxymethyl) melamine [3089-11 -0] (HMMM) to the mbber compound which is in contact with the textile cord. The HMMM resin and resorcinol cross-link during mbber vulcanization and cure to form an interpenetrating polymer within the mbber matrix which strengthens or reinforces the mbber and increases adhesion to the textile cord. Brass-coated steel cord is also widely used in tires for reinforcement. Steel belts and bead wire are common apphcations. Again, HMMM resins and resorcinol [108-46-3] are used in the mbber compound which is in contact with the steel cord to reinforce the mbber and increase the adhesion of the mbber to the steel cord. This use of melamine resins is described in the patent Hterature (49). 

Insoluble Sulfur. In natural mbber compounds, insoluble sulfur is used for adhesion to brass-coated wire, a necessary component in steel-belted radial tires. The adhesion of mbber to the brass-plated steel cord during vulcanization improves with high sulfur levels ( 3.5%). Ordinary rhombic sulfur blooms at this dose level. Crystals of sulfur on the surface to be bonded destroy building tack and lead to premature failure of the tire. Rubber mixtures containing insoluble sulfur must be kept cool (<100°C) or the amorphous polymeric form converts to rhombic crystals. 

Methyl ethyl ketone may also he produced hy the catalyzed dehydrogenation of sec-hutanol over zinc oxide or brass at about 500°C. The yield from this process is approximately 95%. MEK is used mainly as a solvent in vinyl and acrylic coatings, in nitrocellulose lacquers, and in adhesives. It is a selective solvent in dewaxing lubricating oils where it dissolves the oil and leaves out the wax. MEK is also used to synthesize various compounds such as methyl ethyl ketone peroxide, a polymerization catalyst used to form acrylic and polyester polymers and methyl pentynol by reacting with acetylene ... 

Other types of coupling agents include 1,2-diketones for steel,27 nitrogen heterocyclic compounds such as benzotriazole for copper,28,29 and some cobalt compounds for the adhesion of brass-plated tire cords to rubber.30... 

Wire coats good adhesion to brass coated steel wire and to adjoining rubber compounds, tear, fatigue, and age resistance... 

The initial polishing is done to get better adhesion. Decorative articles are polished with a buffing wheel with an abrasive compound such as jeweler s rouge (FejOj) on it. For industrial applications where good adhesion is needed, the surface must be roughened much more. This is done by using a compressed air blast of sand or aluminum oxide on iron and steel or ground walnut shells on brass and bronze. 

Recently, van Ooij et al. have reviewed adhesion of steel tire cord to rubber (van Ooij et al., 2009). The authors reviewed the literature extensively and provided an updated model for adhesion to brass-plated tire cord, which incorporated observations made by many techniques. They discussed the effects of different compounding ingredients and the possible alternatives to the current brass coatings. They note that the use of cobalt compounds improves the adhesion between rubber and brass-coated cords, but new adhesion promoters have been developed as replacements for Co, or for combined use with Co. They also discussed the use of phenolic-resin adhesion promoters. They describe the various techniques that have been developed to study the rubber-brass interface and its aging mechanism. 

Alpha brass coating is used on steel to improve the adhesion of rubber to the steel. It reacts both with sulfur, producing zinc sulfide, and with the rubber. Organic cobalt compounds catalyze the reaction and necessitate high sulfur dosing. Resor-cin-formaldehyde-silica systems are an alternative. The brass layer is not needed if isocyanates are used as the adhesion promoter, although solvents are then required. Aqueous dispersions of chlorinated or sulfochlorinated polyethylenes cross-linked with polynitroso compounds offer an alternative [32]. 

Phenolic novolak resins and high styrene SBR resins are used for reinforcing and increasing the hardness and modulus of rubber compounds. Resorcinol novolak resins are used as a part of the adhesion system between rubber and brass plated steel cord or organic fibers. Both phenolic novolak and resorcinol novolak resins require the addition of a methylene donor such as hexamethoxymethylmelamine (HMMM) or hexamethylenetetramine (HMTA) to fully crosslink and become a thermoset. Phenol, alkyl phenols, and resorcinol can be reacted in bulk or in a polymeric formulation with methylene donors. Typical donors are 2-nitro-2methylpropanol (NMP), HMTA, and HMMM, used to produce a thermoset resin network in the... 

Many rubber composites require that the rubber adheres permanently to a substrate such as steel, brass, textiles or other media. There are a number of established proprietary additives, which may be added to the rubber compound, which function in this capacity. The resorcinol-formaldehyde-silica (RFS) system is commonly used to achieve adhesion to metals. This system relies on the interaction of resorcinol (or a resorcinol donor), a methylene donor snch as hexamethylene tetramine and precipitated silica. Other systems that may rely on cobalt complexes or blocked isocyanates may also be used. 

This chapter will discuss the state-of-the-art of bonding rubber compounds to brass, a technology primarily used on steel tyre cords. The literature is reviewed since 1991 when the previous review was published [1]. An updated mechanism for the rubber adhesion mechanism of brass is presented. Some new developments, such as proposed alternatives to brass, are also discussed. 

If the compound contains an active cobalt-containing adhesion promoter, metallic cobalt precipitates onto the brass surface and also forms the Me-S bond, in addition to copper. Zinc can also form this bond, but does not bond to rubber, as the zinc sulphide growth rate is low (see stage IV). The role of cobalt in NR skim stocks is thus to activate (or... 

Very few recent compound optimisation studies can be found in literature, as they are normally kept proprietary. It has been published that the type of sulphur has little effect on adhesion (pull-out) value. On the other hand, the adhesion increased with ZnO level and with the high-structure carbon black, the former because of the brass activation, the latter most likely because of the increased rubber modulus. Other factors that were identified as affecting the pull-out force were the mixing method and the cure time [30]. 

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