Vulcanized bonding of rubber to metal is a generic phrase that covers all aspects of the process by which an elastomer is chemically bonded to a pre-coated steel surface.

Typically, the process flow consists of the insert being cleaned and degreased, drying the insert, application of a primer coat, drying time, application of the top coat, drying time, and molding of rubber over the insert.

The vulcanization of the bond occurs simultaneously with the cure of the elastomer, as bonding agents are designed specifically to react with the rubber processing conditions. Maximum bond strength is obtained under pressure in compression, injection, or transfer molds.

Motor vehicles use a large number of rubber components, many of which are bonded. To the casual observer they remain hidden by the glossy shell.

• The engine and gearbox units are mounted on a rubber bonded unit that may incorporate hydraulic damping systems to damp out engine noise and vibration more perfectly over a wide spectrum of frequencies.
• The strut units mount the wheels to the vehicle chassis via a shear style rubber bonded bush.
• Sub-frames need to be coupled by stiff mounts that allow some flexibility.
• The steering wheel is joined to the steering rack by bonded components and the various link arms in the suspension and steering all incorporate bonded bushes.

They act together to provide the comfort and road handling characteristics that are demanded in the modern motor vehicle.

Bonded units are also used to correct harmonic vibrations that are sometimes found in the chassis of the lighter, less rigid bodies. Using a rubber bonded mass, called a harmonic damper, that is connected to a vibration node allows the damping of these vibrations.

Rubber seals, gaskets, piston seals (all rubber and bonded), wheel seals, transmission seals, oil seals, AC. seals, pump seals, brake seals, radiator seals, fuel seals, hose, expansion joints, timing belts, boots, track pads, stator motor seal, body mounts, medical / pharmaceutical applications, sporting goods and many more.

Molds do need to be designed to ensure exact balance between cavities and the elimination of trapped gases. The presence of gases can cause a high incidence of bond failures through the 'diesel effect', whereby elements of the bonding agent film burn under the combined effects of heat and high-pressure gas.

Mold design should take in to consideration pressures and temperatures required in the molding process, opportunities for bonding agent to "sweep", and the potential for mold release contamination.

Three essential elements form the core of the bonding process, the rubber, the bonding agents and the substrate.

The selection of the polymer base and the associated compound depends mainly on the product specification. Provided that the rubber can flow into the mold without developing a significant level of cross-linking (less than 2%), a bond can be formed using any rubber compound.