Connector sealing with polyamide hot melt means overmolding the connector body and cable entry by low pressure molding, so the polyamide bonds to the housing and cable jacket and blocks moisture paths in one shot. It replaces separate grommets, potting and heat-shrink steps in many designs. Success depends on three things: a design that gives the melt a continuous bond line, a polyamide grade that adheres to your jacket and housing materials, and leak testing on real parts.
Key takeaways
- Moisture usually enters along the cable jacket and at the housing interface, so the seal must bond to both.
- Adhesion depends on jacket and housing materials; low-energy plastics may need surface treatment.
- Validate with leak, immersion, thermal shock and pull tests on production parts.
Where connectors leak
Water rarely passes through a solid housing. It travels along interfaces: between the cable jacket and the conductors, between the jacket and a grommet, and along the parting line of the connector body. A good seal closes these paths by bonding the encapsulant to the jacket and the housing over a sufficient length.
Process steps
- Prepare: clean surfaces; apply plasma or flame treatment where the jacket or housing has low surface energy.
- Insert: place the connector and cable in the mold and fix the position so the cable stays centered.
- Inject: inject molten polyamide at low pressure to fill around the connector body and cable entry.
- Cool and demold: the polyamide solidifies by cooling; no cure step is required.
- Test: inspect fill, then run leak and pull tests per your plan.
Connector sealing by low pressure molding
- Prepare surfaces
Clean; treat low-energy plastics with plasma or flame. - Insert and fix
Center the connector and cable in the mold. - Inject polyamide
Low pressure fill around the body and cable entry. - Cool and demold
Solidifies by cooling; no cure step. - Leak and pull test
Pressure decay, immersion, thermal shock, cable pull.
Design rules that help the seal
- Bond length: give the melt enough overlap along the cable jacket and housing; longer overlaps resist moisture creep.
- Uniform wall thickness: avoid very thick sections that shrink and very thin sections that fill poorly.
- Mechanical keying: grooves, holes or ribs on the housing let the polyamide lock in place in addition to adhesion.
- Strain relief: extend and taper the molded section at the cable exit so bending stress does not concentrate at the bond edge.
- Gate and vent positions: fill from the thick end toward the cable and vent where air would be trapped.
Material compatibility
| Substrate | Typical adhesion with polyamide hot melt | Notes |
|---|---|---|
| PVC jackets | Generally good | Check plasticizer migration over aging |
| PUR and TPE jackets | Grade-dependent | Test each compound |
| PA6, PA66, PBT housings | Generally good | Keep surfaces dry and clean |
| PE, PP, PTFE | Poor without treatment | Plasma or flame treatment, or mechanical locking |
| Metals | Generally good | Degrease; preheating can help |
These are general tendencies. Adhesion varies with the compound, additives and surface condition, so confirm with samples.
Testing a sealed connector
- Leak test: pressure decay or bubble test on each part or a sample per lot.
- Immersion: test against the required ingress protection target (for example IP67 or IP68 conditions defined by your specification).
- Thermal shock and cycling: repeated hot-cold cycles reveal bond-line separation.
- Pull and bend tests: check cable retention and strain relief.
Polyamides for connector sealing
SILVERSTAR CHEMICAL Co., Ltd. is a polyamide hot melt adhesive manufacturer in Yangsan, South Korea, producing in-house since 2011 with 3,000 metric tons of annual capacity. Its ERAMID polyamides are used for low pressure molding, filters and automotive interiors. Its LPM polyamides are used to encapsulate connectors, sensors and wire harnesses, with UL 94 V-0 flame-retardant grades and grades with heat stability up to 200°C. Read the LPM materials guide or visit the LPM solutions page.
FAQ
Q. Can polyamide hot melt seal a connector to IP67?
Many sealed connector designs use low pressure molding to meet targets such as IP67. Whether a specific design passes depends on bond length, jacket adhesion and processing, so it must be confirmed by testing.
Q. Does polyamide hot melt stick to PVC cable jackets?
Polyamide hot melts generally adhere well to PVC. Check long-term behavior because plasticizers in some compounds can migrate and weaken the bond during aging.
Q. How do I improve adhesion to polyethylene or polypropylene?
These low surface energy plastics usually need plasma or flame treatment, or a mechanical locking feature in the design.
Q. Is a cure step needed after connector overmolding?
No. Polyamide hot melt solidifies by cooling, so parts can be tested and packed right after demolding.
Tell us the application, substrates, operating temperature and required certifications, and our team will recommend a grade and support sample testing. Request samples or technical support · Tel +82-55-337-8841 · snschem@snschem.kr
