Problems Bonding Rubber to Metal

A. Dear Mr. Azeem:

Almost all tire manufacturers solve this problem by bronze plating the steel wire before vulcanizing. They find it to be superior to anything else. Only problem is if you are a roll manufacturer you need some bronze plating shop to work for you, or you need brush plating equipment to do it yourself in your shop.

Good luck,

A. Try plating a thin (1-5 tenths mil) of 70/30 Cu/Zn (brass) prior to bonding.

A. Plate the rolls with electroless nickel. Years ago, someone plated some tire molds, thinking it would help release. It did the opposite and the mold never did come apart. Has to be real rubber to cause this phenomena.

A. In the aircraft industry a considerable amount of bonding of rubber to metals is performed. The cardinal rule for surface preparation is to obtain and maintain a "water break free" surface. Petroleum based products in my experience never exhibited this clean a surface.

A. I am not sure that bronze (Cu/Sn) alloy should be selected but a brass coating (Cu/Zn). Normally a alfa-brass will give a good bonding. Perhaps bronze works - but it is normally brass which is used.

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A. Following things are important.

1. Surface finish and cleanliness of surface.
2. No oxidation on surface.
3. Thickness of primer.
4. Thickness of adhesive.
5. Temperature of curing. ( < 350 °F)

A. Are you using a 2-part agent, i.e., primer coat followed by bonding agent such as Chemisol? Shotblasting followed by degreasing should give a good enough surface for the primer to adhere. Try different degreasers. Note that ANY oils getting onto the bonding agent will prevent rubber bonding. Touching the agent with ungloved hands can be enough.

Pre-cure of the bonding agent could also be taking place. Are you using heat to dry it?

A. 1-surface cleaning with methylene chloride or machining the metal shaft with a lathe
2-applying primer bonding agent
3-applying over coat bonding agent or top coat
4-curing temperature not less than 150 °C step wise
5-if any problem appears in this case the rubber compound has excessive accelerators and should be minimized and the lubricant oil is not compatible with the rubber and bonding agent.

A. Metal preparation seems to be the fault. The procedure should be to;
1. Grit blast using sharp iron grit for steel (maybe 350 micron sharp iron grit)and aluminium oxide for non-ferrous metal. If a new mandrel is used, it needs degreasing before grit blasting as well as afterwards.
2. De-grease using clean solvent (handle with clean gloves afterwards)
3. Coat a thin layer and air dry in a clean environment(usually brush applied on small rollers). Some rubbers (e.g. NBR, VMQ, FKM) can be bonded with one bonding agent, others need a top coat (which bonds to the first coat and rubber).
4. Wrap the rubber strips tightly, especially at the ends to prevent steam wicking along the bond line. N.B. some porous metals (e.g. aluminium) may need the first coating baking to prevent steam ingress from beneath.
5. Step curing is dependent on the rubber cure and does not usually effect the bond for NBR. The NBR will shrink onto the mandrel and add compressive force to the bond line. Some rubbers that need step cures to emit off-gas include silicone, FKM, vamac.

Take care not to bond in a dusty environment or where release agents are being used

Hope this helps.

A. Exposing polymers like rubber and PVC to air or oxygen plasma increases the surface energy of these materials. This is said to be due to cross linking of polymer chains. The effect can be easily checked by placing a drop of water on the untreated surface. It remains a blob, while on plasma treated surface it spreads easily, i.e., it wets the surface. This property helps in improving the bonding considerably.

A. Sir:

While working for one section of a company, another section (the potato digging equipment section) asked me about bonding rubber to steel. I did not know the answer but I did see rubber bonded to steel in the potato digging machine.

Regards,

A. One method, often used for bonding reinforcing wire in tires, is to first brass plate the steel.

A. Hi Virendra,

To me you are using the wrong preparation of the Aluminum, I would expect a minimum of a conversion coating such as MIL-C-5541 chromate conversion coating, but ideally would want chromic acid anodizing (MIL-A-8625 Type I). A blasted surface oxidizes very quickly, meaning the bonding can be rather hit and miss.

Hi Naeem. Sorry, I can't help because I know nothing of that subject.
But to capture readers' interest and replies, please do your best to explain your own actual interesting situation. Abstractions rarely attract any responses. Good luck.

Regards,

A. Rubber is hydrophobic ( water repellant) and water ( or other adhesives) does not wet it. That makes bonding difficult. Exposing rubber to a low temperature plasma makes it hydrophilic and increases its surface energy. Bonding would then be simple. If required blackened ms may also be plasma treated.

A. We use a product from Lord 208A which is a primer with their Autoseal 3370 adhesive for rubber. End use automotive.

 Dear Ronald Zeeman,
thank you for your valuable advice.

Best regards,