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Precision Acoustics

Aptflex F3S

Aptflex F3S is a two-part, high-performance encapsulation material. It is very tough and durable with an acoustic wave speed similar to that of seawater.

If you have any specific questions about this product, please contact us.

aptflex f3s with sample


Aptflex F3S is a two-part, high performance encapsulation material.  It is the toughest and most durable encapsulant material in the range from Precision Acoustics Ltd.  It has excellent hydrolytic stability and an acoustic wave speed similar to that of seawater.  It has slightly higher absorption and is less flexible than other encapsulants.

These properties make Aptflex F3S an ideal system for hydrophone potting, marine encapsulation applications or as an acoustic window.

Aptflex F3S is particularly useful where the component being potted may be subject to abrasion since it is more capable of withstanding such wear than our other encapsulants.

Key features

  • Flexibility and resistance to temperature extremes of -50 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
  • Moderate insertion loss and ultrasonic absorption

Technical specifications

AppearanceNatural (Straw colour)
Density Part A1.05 g/ml
Density Part B1.01 g/ml
Mix ratio7.3:1 (By Weight A:B)
Cured density1.04 g/ml
Initial mixed viscosity70 poise at 25 °C
Usable life25 minutes at 25 °C
Gel time50 minutes at 25 °C
Curing times:24-48 hours at 25 °C
over night 30 °C
6 hours at 50 °C
4 hours at 80 °C
Hardness75-80 Shore A
Tensile strength8.6 MPa
Elongation at break1000%

Precision Acoustics reserves the right to change the specification without notice

The shelf-life of unopened sachets is at least 12 months.


This product is subject to Dangerous Goods Movement control.

Please note this will typically incur an additional £270.00 surcharge for shipments outside the UK.