Products I know
Metal-to-rubber bonding: getting moulded parts to hold.
Metal-to-rubber bonding agents are coatings applied to metal inserts before rubber is moulded onto them. During vulcanisation they form a chemical bond between rubber and metal that should be stronger than the rubber itself. They are essential in anti-vibration mounts, bushes, seals and rollers.
Where they are used
- Engine and suspension mounts, and anti-vibration mounts for machinery.
- Bushes and centre bearings in automotive suspensions and drivelines.
- Oil seals and rubber-coated rollers.
- Industrial dampers, couplings and rubber-lined components.
The process decides the bond
- 1CleanDegrease the metal inserts completely.
- 2PrepareGrit or shot blast, or phosphate, for a clean, active surface.
- 3CoatApply primer and cover coat at the right film thickness, by spray or dip.
- 4Dry and storeDry properly and protect coated parts from dust, moisture and handling.
- 5MouldMould and vulcanise. Avoid pre-curing the coating before the rubber reaches it.
Reading a failed bond
Bond tests are judged by where the failure happens. If the rubber tears and leaves rubber on the metal, the bond held and did its job. If the rubber peels cleanly from the coating, or the coating peels from the metal, the problem is in the process: surface preparation, film thickness, storage of coated parts, or a mismatch between the bonding agent and the rubber compound.
The rubber compound matters too. Natural rubber, nitrile and EPDM each need a suitable bonding system, so a change of compound should always trigger a new bond check.
How I help
Rubber-to-metal moulders supply automotive and engineering OEMs, so a bonding agent change goes through careful trials. I help bonding-agent makers reach these moulders, and help moulders run trials with clear criteria. See automotive.
Questions people ask
Why do I need both a primer and a cover coat?
The primer bonds to the metal and protects it; the cover coat bonds to the rubber during vulcanisation. Some one-coat systems exist, but two-coat systems are common for demanding parts.
What does it mean when rubber peels cleanly off the metal?
It points to a process problem, not a rubber problem. Check surface preparation, coating thickness, how long and how coated parts were stored, and whether the coating pre-cured in the mould.
Does changing the rubber compound affect the bond?
Yes. Different polymers and cure systems need suitable bonding agents. Re-test bonding whenever the compound changes.