ASI 388



ASI 388 Electronic Grade RTV Silicone is a one part, moisture cure sealant that cures to form a tough, durable, flexible rubber that is deal for bonding, sealing, encapsulating and protecting electronic parts.

Once cured, ASI 388 will withstand a constant temperature range of -70°F to 400°F and will resist some chemicals depending on duration, contact and the type of chemical. ASI 388 bonds to a wide variety of substrates which makes it ideal for protection against moisture and other external variables. ASI 388 exhibits consistent electrical properties even when subjected to environmental changes in temperature, humidity, etc., making it a good insulator for electronic components.


  • Non-Corrosive, Electronic Grade
  • Heat & Cold Resistant
  • Excellent Electrical Properties
  • Long-Lasting Durability
  • Resistant To Some Chemicals
  • Good Stress Relieving Properties
  • Excellent For Bonding, Sealing, or Encapsulating
  • Advanced Adhesion To Various Substrates

Physical properties

Physical PropertiesTest MethodResult
ViscosityASI Test Method1,000,000 cps (Spindle 7, 4 rpm)
Skin Formation TimeASI Test Method20 minutes (70°F, 50% RH)
DensityASTM D14758.5 lbs./gal
HardnessASTM C66130 (Shore A)
Modulus 100%ASTM D4120.37 MPa
Tensile StrengthASTM D412300 psi
Elongation at BreakASTM D412600%
Application TemperatureASI Test Method-35°F to 150°F
Gun GradeASI Test MethodPass (Non-Slump)
QUV TestingASTM G154Pass (10,000 hrs.)
Service TemperatureASI Test Method-70°F to 400°F
Dielectric StrengthASTM D149500 (Volts/Mil)
Volume ResistivityASTM D2573x10**15
Dielectric Constant 50HzASTM D1503
Dielectric Factor 50HzASTM D1505x10**-3
Typical Cure RateASI Test Method24 hrs. (1/8" bead)

Strength will start to develop immediately and continue increasing for 7 days after application. ASI recommends testing strength and adhesion on the 7th day. ASI 388 suggested application temperature range: -35°F to 150°F. ASI 388 can be used at temperatures higher than 400°F for intermittent periods. Testing should be done to confirm temperature requirements are met.

Information on this data sheet can change without notice and it is therefore not recommended that these figures be used in spec writing. If you have any questions contact manufacturer’s sales and technical service department.

Conforms / Meets / Exceeds

  • UL Recognized
  • VOC Compliant (21 grams/liter ASTM D2369)

Common Substrates

  • Glass
  • Most Metals
  • Most Fiberglass
  • Most Wood Types
  • Aluminum
  • Porous Surfaces
  • Vinyl
  • Rubber
  • Natural & Synthetic Fiber
  • Most Painted Surfaces
  • Some Plastics

Common Applications

  • Sealing Lead Wire Entries
  • Waterproofing Electronics
  • Component Mounting
  • Adhesive Use Around Electronics
  • Sealing Electronic Assemblies

Speak with a sales engineer to discuss ASI 388 or any of our other products or manufacturing services! Use our contact form or call 800-325-7040 now.