53Rubber-metal products are widely used in different branches of industry. The work efficiency and durability of such items depend on the strength of the bond at a rubber-metal boundary. If a chemical interaction takes place between metal and rubber, the strength of bonding is high and does not reduce even upon heating to 100°C. When the bonding strength is determined only by the intermolecular interaction forces, the strength between rubber and metal significantly reduces with temperature increase. Rubbers are usually attached to ferrous metals and stainless, heat resistant, and acidproof steels, as well as to some nonferrous metals and alloys thereof (titanium, magnesium, copper, bronze, brass, duralu minum, and so on) [1].To join rubber and metal, the methods of hot bond ing via vulcanization and cold bonding are used. Upon cold bonding, vulcanized rubber, which is glued to the metal surface, is used. To bond butadiene, butadienestyrene, and natural rubbers to steel and duralumi num, an 88NP adhesive or Khemosil X6025 adhesive is used in combination with a Khemosil 211 primer. Hot bonding of rubber to metal via vulcanization is carried out through an intermediate layer of ebonite, brass, or rubber adhesive. Independently of the bond ing technique, the metal surface must be preliminary purified from the oxide layer and oil and grease traces.
Hot BondingThis method of joining of resin to metal is the sim plest and cheapest, providing the sufficient thermal stability and resistance to dynamic loads. At the begin ning of vulcanization, the unvulcanized rubber mix ture stays in a viscous flow state, which allows good contact with metal. Hot bonding can be performed without the application of special adhesives. However, the greatest strength of the bond is observed upon glu ing of rubbers to brass plated metal surfaces.
Bonding Using BrassingThe bonding of rubber to metal via brassing finds application mainly in production of automobile tires. This method provides high strength and the highest thermal stability of the bonding of natural or isoprene rubbers to metals, as well as good resistance of the resulting products to shock and vibrations. The strength of rubber bonding to metal prepared by this method depends to a great extent on the composition of brass and rubber mixture [1].It is though [7] that, to form a strong adhesion bond, the thickness of the brass coating needs to vary within 0.20 µm and the optimal content of copper in the coating should compose 69%. Such brasses ensure better retention of the adhesion properties during aging.The greatest strength of rubber bonding to a brass coated metal surface is reached upon vulcanization in presses under a pressure of no less than 2-3 MPa. It increases up to the attainment of a vulcanization opti mum and changes further only insignificantly.The strength of rubber bonding to metal also depends on the composition of the rubber mixture (no plasticizers migrating to the surface are permitted) and dynamics of the vulcanization process. If the rubber mixture stays for...
