Polyamide to EPDM rubber bonding

[Henry Chiansky]

We have been overmolding rubber cables (specifically SJOOW and H07RN-F types) using a low-pressure molding process. The material used for molding is polyamide, which is typically the go-to polymer for overmolding applications. However, since we are working with rubber cables, achieving optimal adhesion between the polyamide and the rubber surface is crucial for our application.

I would appreciate guidance on the process. Are there any specific primers that should be used to enhance adhesion? Should we treat the surface of the rubber cables with IPA alcohol, or would roughening the surface improve the bond? Any tips or advice on surface preparation, treatment, or process optimization would be highly valued!

 

[btrueblood]

I would talk to the cable manufacturer about the specific compounds used in their outer jacket.

If they are unresponsive, the next place to look for help would be Lord Chemicals - they sell adhesive primers for rubber, which in general will result in bonding that is stronger than the parent material.

One issue you will likely still have is matching the stiffness of the cable and jacket with the overmolding you are doing. Hopefully your compound has a low stiffness to better match the cable flex, and you have plenty of axial length to taper out (strain relief) the part you are overmolding. You are also probably using a low temperature polyamide, to avoid reversion in the cured rubber cable jacket and wire insulation?