Two-component (2K) polyurethane adhesives are common in sandwich panels, caravans, building elements and composites. The key to success is correct mixing.
Components
- Component A (polyol): Usually the filled, coloured component.
- Component B (isocyanate / hardener): Must be protected from moisture.
The ratio is typically given as 100:20 by weight or 2:1 by volume. An out-of-tolerance mix means a joint that stays soft and tacky or becomes brittle.
Mixing methods
| Method | Use |
|---|---|
| Manual mixing | Small batches, repairs |
| Twin cartridge + static mixer | Medium volumes, homogeneous mix |
| Meter-mix machine | Series production, panel lines |
Pot life and open time
Pot life is how long the mix remains applicable. Open time is how long after application parts can still be joined. They are not the same, and both shorten with temperature.
Practical tips
- Close the component B container immediately after use; moisture causes foaming and crystallisation.
- In summer, mix in small batches; large batches heat up and gel early.
- Verify machine dosing with a ratio test at the start of each shift.
- Discard the first few centimetres from a static mixer; the mix may not be homogeneous.
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