NPL Aptflex F21 supplied as a two-part mix
Aptflex F21 is a two-part, high performance encapsulation material, exhibiting toughness, excellent hydrolytic stability and an acoustic wave speed similar to that of seawater.
These properties make Aptflex F21 an ideal system for hydrophone potting, marine encapsulation applications or as an acoustic window.
Aptflex F21 is particularly useful where small delicate components are potted since the material exhibits low shrinkage and hence stress during the cure phase.
Part A is solid at room temperature and must be warmed at 40°C for two hours before use.
The main features of Aptflex F21 are:
- Flexibility and resistance to temperature extremes of -50°C to 100°C
- Low moisture sensitivity during the cure phase
- Excellent hydrolytic stability
- Excellent electrical insulation properties
- Acoustic wave speed similar to that of seawater
- Very low transmission loss
Typical Physical Properties of Aptflex F21 are:
| Appearance | Black |
| Density Part A | 0.91g/ml |
| Density Part B | 1.22g/ml |
| Mix Ratio | 3.35:1 (By Weight A:B) |
| Cured Density | 1.050g/ml |
| Initial Mixed Viscosity | 50 poise at 25°C |
| Usable Life | 25 minutes at 25°C |
| Gel Time | 50 minutes at 25°C |
| Curing times are temperature dependant: | 24-48 hours at 25°C |
| Hardness | 80-85 Shore A |
| Tensile Strength | 12MPa |
| Elongation at Break | 300% |
The shelf life of unopened sachets is at least 12 months.
