Overmold Material Adhering to Cable

You will have significant difficulty osing true overmoulding processes to achieve any bonding. The cable sheath is not anywhere near HTD of the material and so there will be no surface "mixing" of the two materials.

We did find success using a material that was vegetable based (effectively hot-melt adhesive) as an overmould for moisture protection.

This did create some challenges to get the parts to release from the mould tool, but was achievable. Tooling was Aluminium and thus very cheap and easily cooled and the injection process was single stage pneumatic.

If you search for "Optimelt" you might find something relevant.

Process is used in automotive application to water/humidity protect electronics in engine compartment and other similar harsh locations.

Hi Guru,

Hope you're well.

Just trying to find solutions to adhere polyurethane OM to LSZH cable jacket.

We have used a product called Macromelt which is a mixture of Hotmelt and Nylon. It does have better adhesion, but it is not good for use in larger overmolds as it will easily crack apart when flexed.

We also tried a plasma treatment that is supposed to "open up the surface" to provide greater surface area and better adhesion, but it was a total failure. We sent samples to the company and they couldn't even tell which parts had the plasma treatment and which didn't.

Often the difficulty of overmolding onto flexible PVC insulating outers is the migration of the PVC plasticizer to the outer surface. We have had great success with an acetone wipe of the last inch of the target cable outer, immediately prior to overmolding. Fresh acetone (use a small lab solvent dispensing pump/bottle) and fresh paper wipe (little 4" squares, perforated on a roll, often found in supermarkets and grocery stores) will guarantee you don't build up plasticizer goop.

Mark Bingham
Relativity PL

In underground wiring, where water ingress is a major concern at distribution voltages, the problem is addressed somewhat differently. The insulation material of the connector is often EPDM or EPDT, neither of which bond particularly well to either PVC or xlinked PVC. The answer became molding a connector assembly that would accept an insertable connector attached (crimped) to the delivery wire that could be snapped permanently into the connector assembly through a dielectric filled, friction fit cavity. The cable connector assembly could then be fitted to the mating device connector.

Bob