Where hot melts are used in a filter
In filter manufacturing, hot melt adhesives join the pleated media, seal its edges and bond the media pack to end caps or frames. If any of these bonds fails, unfiltered air, oil or fuel bypasses the media. The adhesive therefore has to match both the production line and the conditions the filter sees in service.
- First/last pleat joining: closes the seam of the pleat pack.
- Pleating and edge sealing: keeps pleat spacing stable and seals the edges.
- End cap bonding: fixes the media pack to metal or plastic end caps.
- Frame bonding: bonds panel filters to their frames.
Air filters vs oil and fuel filters
| Item | Air filters (HVAC, cabin, industrial) | Oil and fuel filters |
|---|---|---|
| Main stress | Airflow, humidity, moderate temperature | Hot oil, fuel, pressure pulses, vibration |
| Key adhesive property | Fast set, good adhesion to media and frame, low odor | Oil and fuel resistance, heat resistance, adhesion to metal end caps |
| Typical chemistries | EVA, PO, polyamide | Polyamide, PUR |
Hot melt chemistries compared
The table below shows general tendencies. Actual performance depends on the specific grade and test conditions.
| Chemistry | Heat resistance | Oil and fuel resistance | Set mechanism | Notes |
|---|---|---|---|---|
| EVA | Low | Low | Cooling | Economical, common in air filters |
| PO (APAO) | Medium | Low to medium | Cooling | Good adhesion to nonpolar media |
| PUR (reactive) | High after cure | High after cure | Cooling plus moisture cure | Needs curing time and careful handling |
| Polyamide | High | High | Cooling (immediate) | Fast set with oil and heat resistance |
Selection checklist
- Service conditions: maximum temperature, contact with oil, fuel or water, pressure pulses.
- Substrates: cellulose, synthetic or glass fiber media, and metal or plastic end caps.
- Line conditions: application method (bead, extrusion, dipping), line speed, required open time and set time.
- Viscosity at application temperature, which controls bead shape and penetration into the media.
- Compliance: VOC and halogen content, and any customer specifications.
How to test a filter adhesive
- Immersion test: immerse bonded specimens in the actual oil or fuel at service temperature, then check weight change, appearance and remaining bond strength.
- Adhesion after aging: compare bond strength before and after heat aging.
- Finished filter tests: run the customer's own filter performance and durability tests on real parts.
SILVERSTAR CHEMICAL filter polyamides
SILVERSTAR CHEMICAL Co., Ltd. (brand ERAMID) manufactures polyamide hot melts in Korea for pleat joining, edge sealing and metal end cap bonding in industrial air filters and oil and fuel filters. The materials are VOC-free and halogen-free and are designed for heat and oil resistance. Custom viscosity and open time can be developed for specific lines, and samples are available for qualification.
Polyamide for filters → · Company FAQ →
FAQ
Q. Which hot melt adhesive is used for oil filter end caps?
Polyamide hot melts are widely used for oil and fuel filter end caps because they bond to metal and filter media and keep their strength in hot oil and fuel.
Q. Can EVA hot melt be used in oil filters?
Standard EVA hot melts soften at lower temperatures and swell in oil, so they are generally used for air filters and less demanding applications rather than hot oil or fuel filters.
Q. What is pleat joining in filter manufacturing?
Pleat joining (first/last pleat joining) closes the seam of a pleated filter pack so that the media forms a continuous cylinder or panel without bypass.
Q. Why is open time important for filter adhesives?
Open time determines how long the adhesive stays tacky after application. It must match line speed: long enough to position the media or end cap, short enough to set quickly.
Q. Does SILVERSTAR CHEMICAL supply filter adhesives?
Yes. SILVERSTAR CHEMICAL supplies polyamide hot melts for pleat joining, edge sealing and metal end cap bonding in air, oil and fuel filters, and supports sample testing.
