Brass-plated steel tire cord adhesion

Resorcinol formaldehyde resin is an extremely important component of the HRH system for achieving good rubber-to-brass-plated steel tire cord adhesion. This RF resin functions as a resorcinol donor in the rubber compound that reacts with the... 

Zinc oxide is essential in rubber technology because it is the most commonly used activator for sulfur cure systems. Just about every rubber compound that uses sulfur as the vulcanizing agent will most likely contain a small amount of zinc oxide to activate the cure. Also zinc is alloyed with copper to form brass. Special brass-plated steel tire cord is a primary reinforcing material for producing steel-belted radial tires. The brass coating of the steel tire cord enables very good rubber-to-metal adhesion. Therefore, zinc metal and zinc oxide are very important to the rubber industry. 

DCBS is a commonly used sulfenamide accelerator that is selected when good scorch safety is needed combined with a relatively slow cure rate. The selection of DCBS is particularly useful when a slow cure rate is needed to optimize rubber adhesion to brass-plated steel tire cord. 

The adhesion between rubber and brass-plated steel (e.g., steel tire cords for belted radial tires) has been the subject of much study and speculation. Brass plating is the major method of obtaining adhesion between natural rubber and the steel of tire cords. Over the years there has been much speculation about its mechanism, but there is agreement on one aspect of the adhesion of natural rubber to brass-plated steel the actual adhesion between the natural rubber and the brass-plated cord, formed in situ during the vulcanization process, is an interfacial layer of sulfides and oxides of copper (Buchan, 1959 van Ooij, 1979, 1984). 

Another market appHcation for naphthenic acid is the tire industry, where cobalt naphthenate is used as an adhesion promoter (see Adhesives Tire cords). Cobalt naphthenate improves the bonding of brass-plated steel cords to mbber, presumably by suppressing the de-zincification of brass (50). Its first reported use was in 1970 and the first patent for its use was issued in 1975 (51). About 900 t of cobalt naphthenate is used worldwide as an adhesion promoter, half of it in North America. The unit value fluctuates between 8.75—13.25 /kg because of the volatility of cobalt prices. Although it is the industry standard, the use of cobalt naphthenate is declining with the advent of more economical high metal-containing substitutes. 

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. 

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. 

The adhesion between rubber and brass-plated steel (e.g., steel tire cords for belted radial tires) has been the subject of much study and speculation. 

Steel tire cord is usually brass plated in order to achieve good rubber-to-metal adhesion. Also, tire bead wire is commonly plated with bronze to achieve rubber-to-metal adhesion. The steel cable used in rubber mining belts may also be brass or bronze plated. 

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... 

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