Sealed connectors and overmolded cable harnesses in fluoropolymers
Industry: Cable harnesses and connectors for military vehicles, naval systems and aircraft
Technology: Atmospheric plasma (PlasmaTEC-X), corona treatment for cables (CableTEC), vacuum plasma (VacuTEC)
Fluoropolymer insulation is chosen because almost nothing affects it, and that is exactly why almost nothing sticks to it. Overmoldings and sealants then release from the cable, and water, salt and fuel find their way into the connector. Plasma treatment of the sealing zone gives the overmold or sealant a surface it can bond to, without the hazardous chemical etching traditionally used.
The challenge
Cables in defense platforms are exposed to fuels, hydraulic fluids, salt water, UV and extreme temperatures. That is why insulation and jackets are often made from fluoropolymers such as PTFE, FEP, PFA and ETFE, or from other low-energy materials like silicone and polyolefins.
At the transitions, these cables must be sealed. Connectors are overmolded, backshells are potted, and branches are sealed with adhesives or adhesive-lined sleeves. All of these depend on adhesion to the cable surface.
On an untreated fluoropolymer, the overmold or sealant holds only mechanically. Under vibration, flexing and thermal cycling, a gap opens at the interface. Moisture then wicks along the cable into the connector, where it causes corrosion, insulation faults and intermittent failures that are hard to trace.
Why conventional methods fall short
- Chemical etching of fluoropolymers works, but involves hazardous chemistry, special handling, discoloration of the insulation and waste treatment.
- Mechanical roughening gives limited grip and can damage thin insulation.
- Primers add a step, cure time and another material to qualify, and they do not solve the underlying low surface energy on their own.
- Designing around the problem with extra clamps and seals adds weight and assembly time.
The solution
Plasma treatment changes the outermost molecular layer of the polymer. It removes contamination and adds polar groups, so the surface energy rises and the overmold material or sealant can wet and bond to it. The bulk properties of the insulation, which were the reason for choosing it, are not affected.
On harness and connector assembly, an atmospheric plasma nozzle treats the exact zone that will be overmolded or sealed, immediately before the molding or sealing step. Connector bodies, backshells and inserts in plastic or metal can be treated the same way.
For continuous cable production, a corona or plasma station built around the cable treats the jacket inline. This prepares the whole surface for later sealing, printing or marking. Small components can be treated in batches with vacuum plasma.
How it fits into production
- Material trials. The customer’s cable types and overmold or sealing materials are tested in Tantec’s laboratory, with adhesion compared before and after treatment.
- Choice of technology. Zone treatment at the Molding station, inline treatment on the cable line, batch treatment of components, or a combination.
- Integration. Nozzles or treatment heads are mounted at the molding or assembly station or on the cable line, with signals to the line control.
- Verification. Surface energy is checked during setup and as routine control.
Why Tantec
- Dedicated equipment for cables and tubes as well as plasma for connectors and complex parts, from one supplier.
- Long experience with difficult polymers, including fluoropolymers used in aerospace and defense wiring.
- A dry alternative to chemical etching, with no hazardous baths or waste.
- Laboratory testing on the customer’s own cables and materials before investment.
- Standard units and custom solutions for both assembly stations and continuous lines.
Is this your challenge?
If your overmoldings release from the cable, your seals let moisture into connectors, or you want to replace chemical etching, send us cable and material samples. We will test them and show you the difference at the interface.