Understanding low outgassing adhesives

The right applications
The first thing to understand about low outgassing products is when to use them (see “Typical outgassing applications” for a full list). Other than space systems, the most common applications for low-outgassing products are those that involve optical or electrooptical components, which can be clouded or fogged by outgassed chemical compounds. Outgassing can also affect some sensitive electrical processes—by interfering with electrical continuity. Semiconductor manufacturing processes can be very sensitive to outgassing material systems. And commercial vacuum processes can also suffer from outgassing issues.

If you suspect outgassing could potentially pose a problem in your application, specifying adhesives that comply with the ASTM outgassing standard will make sense as long as one of the compliant grades meets all of your other technical requirements. And the good news here is that low outgassing adhesives don’t typically require any sacrifice in other mechanical or physical properties. What sets low outgassing products apart from their generic counterparts is that the low outgassing grades have passed the rigorous ASTM test—often after months of painstaking formulation work on our part.

The time and expense of all that testing and custom formulation do not have major cost implications for users of low outgassing products. The compelling reason to carefully consider whether you truly need a ASTM E595compliant grade comes down to freedom of choice, not cost.

Consider that Master Bond has hundreds of adhesives that have not been tested for low outgassing and over 20 adhesives that have. By picking an ASTM E595-compliant grade when you do not need one, you may limit your ability to find the best match between your application requirements and adhesive properties. For this reason, engineers should stick with standard products for bonding, sealing, encapsulation and potting applications that have no known sensitivity to outgassing.

With that caveat in mind, the compliant adhesive products available today do cover a wide range of capabilities for those times when nothing else will do (see Figure 1 and Table 1). Master Bond offers ASTM E595 products for structural bonding, potting, encapsulation and sealing.

Also available are E595-certified electrically and thermally conductive products as well as medical and cryogenic adhesives. Recently, Master Bond introduced a UV-curable adhesive, one of the first in the industry to pass the standard ASTM E595 test.