ASI 388

Electronic Grade RTV Silicone

ASI 388 electronic grade silicone is a one-part, moisture- curing RTV (room temperature vulcanizing) silicone sealant/adhesive that is non-slump and cures to form a tough, permanently flexible rubber.

The non-corrosive curing system of ASI 388 electronic grade silicone makes it ideally suited for protecting, sealing and insulating corrosion-sensitive electronic and electrical materials such as copper, brass, silver, etc.

ASI 388 has been specifically formulated for use in electrical/electronic production and assembly because it:

  • has good dielectric properties
  • has high surface resistivity
  • resists electrical tracking
  • repels water to protect electrical properties

ASI 388 electronic grade silicone is a neutral-cure silicone that emits no objectionable odors during cure and is ideally suited for use in confined areas. However, adequate ventilation should be provided when ASI 388 is used in large-scale production.

ASI 388 is a 100% silicone and has excellent resistance to:

  • ozone
  • UV
  • airborne chemicals
  • temperature changes from -57 C to   +204°C (-70°F to +400°F)


ASI 388 electronic grade silicone is an excellent sealant/adhesive for many electrical and electronic applications where corrosion to metals, particularly copper, brass, silver, etc., is a problem. Such applications include:

  • lead-wire entries
  • conduit terminal boxes
  • component mounting
  • electrical connections
  • conduit ends
  • splices
  • cover plates
  • coaxial cable connectors
  • printed circuit boards
  • conductor entry holes


All surfaces should be clean and dry. It is recommended that bonding surfaces be solvent wiped with oil-free solvents, such as xylol, toluol naphtha or non-flammable chlorinated solvents. Do not wipe with oil-based solvents such as Varsol. Allow surface to dry thoroughly before applying sealant.


ASI 388 electronic grade silicone is ready to use and requires no mixing or additives. The cure mechanism begins as soon as the sealant comes in contact with the air. At conditions of 25 C (77° F) and 50% relative humidity, the sealant will skin in 15 minutes and fully cure within 48 hours (1/8 bead).

Higher humidity accelerates cure. Tooling should be done before skinning takes place.

In applications where partial total confinement of sealant is prevalent, the time required for proper cure is lengthened by the degree of confinement.


Priming of ASI 388 electronic grade silicone is normally not required for application to most substrates.

Unprimed adhesion can be readily tested by applying a small trial bead and allowing 7 days for maximum adhesion to occur.

If primer is required, contact ASl for technical assistance.


ASI 388 is available in clear and white. Special colors are available upon request. Call for price and availability.


ASI 388 meets the requirements of MIL 46l06 Type 1.

About American Sealants, Inc.

Since 1987 American Sealants has become a recognized and trusted manufacturer, supplier and packager for some of the biggest brand name adhesive and industrial companies in the United States. American Sealants Inc. has grown due to its manufacturing capabilities, core values, and quality control processes. As a leader in the industry, our experienced customer service and technical team are here to ensure your satisfaction. You can be assured that you are receiving a quality product. We do not cut corners to provide cost savings – rather we offer a high performing product at a competitive price through our capabilities and processes. If you do not see something listed on our website, please do not hesitate to call and ask. With our experience we can help you get moving in the right direction.