Rubber-to-metal bonded products are used in the appilication where combining the flexibility of rubber with the strength of metal. Appilictions are such as damping, bonded piston for transmission, magnetic encoder ring, washer for HVAC.
Rubber and metal are two different materials with huge differences in chemical structure, physical and mechanical properties.
Therefor,rubber-to-metal bonding process, specifically rubber metal bond and rubber to steel bonding, is developed in order to combine rubber and metal together. This bonding technology invovles a range of scientific fields such as surface physics, polymer chemistry and mechanics.
Key Process of Rubber to Metal Bonding
Rubber-to-metal bonding process including steps:
1.Metal Surface Treatment ->2.Apply adhesive onto metal part –> 3.Rubber vulcanization with metal part
1. Metal Surface Treatment:
The first step in rubber to steel bonding involves preparing the metal surface. Treatments remove rust and oil residues, ensuring that the metal surface has the appropriate roughness for bonding.
Typical method used for metal surface treatment is chemical treatments:
Acid/alkali washing, phosphating, high-temperature degreasing, and surface plating.
It’s important to balance the metal surface roughness; if too rough, adhesive wetting is compromised, leading to gas adsorption and weak bonding areas.
2.Apply adhesive onto metal part
The adhesive for rubber metal bond applications belongs to one of three categories:
1)Phenolic Resins
2)Polyisocyanates
3)Halogenated Polymer
The choice of adhesive must match the vulcanization characteristics of the rubber. For example, polyurethane rubber using a peroxide vulcanization system has a better cross-linking matching effect with phenolic resin and isocyanate adhesives.
When applied as a pre-coating, the adhesive penetrates the metal surface’s pores and grooves, displacing air and establishing strong contact with the metal.
On the rubber side, the adhesive forms a bond through the diffusion of molecular chains, co-crosslinking, and other physical and chemical interactions.
3.Rubber vulcanization with metal part
The final key steps in rubber metal bonding is the process of vulcanization where rubber and metal part are placed in the tooling. It is the process of compressing and heating the rubber.
Pressure,temperature and time need to be control for vulcanization process. vulcanization process not only affect the chemical cross-linking of the adhesive, but also affect the physical properties of the rubber. If the vulcanization parameter is not well controlled, the adhesive may not be fully cross-linked or the rubber properties may deteriorate, ultimately affecting the bonding strength.
For more details, contact OBT Rubber Seal for customized rubber metal bonding product solutions according to your applications.
