Bonded rubber is a natural or synthetic elastomeric substance that is permanently adhered to another hard material, usually metals like steel grades, aluminum and brass, although rubber is bonded to glass and plastic as well. The rubber is at first uncured, then injected or poured into a mold containing the metal substrate. The substances making up the rubber material must not bleed rapidly to the surface of the uncured stock.
Any type of rubber can be bonded to another harder material, including natural, pure rubber, neoprene, silicon, EPDM and nitrile. Each of these rubber compounds have unique benefits and qualities, including temperature resistance, water resistance, durability, ability to withstand high psi, continuous wear and contact with oil or chemicals.
With each specific rubber offering unique capabilities, many manufacturers of rubber bonded to metal procedures offer custom design options so that the customer may get exactly what they want. Rubber effectively forms a water and air tight seal with metal with the use of an adhesive coating between the two.
Types of adhesives that work well between metals and rubbers include industrial adhesives such as silicone and polyurethane. This forms many different products, usually for industrial rather than commercial use, including medical instruments, bearings, gears, plugs, washers, vibration dampeners, rubber lined tanks, building construction components, rubber-lined piping systems and many others.
There are three main components within the rubber to metal bonding process: the metal substrate, the rubber material and the adhesive agents that bond the two together. The process of forming the bonded product is simple, but depending on the type of metal and rubber used, could take over an hour to complete.
The substrate must be thoroughly cleaned and degreased before the bonding can start. Then, it is coated with a primer and top coat of adhesives, either solvent or water based. Then the most important part of bonding, the molding process, takes place next. The rubber material is heated and injected or poured into the mold cavity that now contains the metal substrate.
Once the mold is filled and the metal component is positioned perfectly, the rubber is given a chance to cure and is then removed from the mold when dry. Sometimes plated inserts are added into the mold to enhance strength and durability of the part.
Bonded rubber and metal products are durable, long lasting and are bonded together to form an extremely strong seal. The bond is actually stronger than the elastomeric rubber itself, so if there is product failure, it lies in the rubber’s inability to withstand pressure.