What IS the Difference Between an Adhesive and a Sealant?

Posted on 5/21/2020 10:52:21 AM By ASC

Adhesives and sealants are often seen as veteran partners that are joined at the hip, but while they often work together, they perform different but equally vital functions in manufacturing.

It would be simplistic to define their differences as being that adhesives bond, while sealants seal. The truth is that while the one’s primary function can almost trespass on the others due to certain overlapping in their requirements; they for the most part adhere to their primary uses while taking on some of their partner’s qualities when necessary.

Sealants are used to seal joints and assemblies as well as fill any gaps between objects or substrates. But it doesn’t stop there. They need to provide a certain amount of adhesion so the seal remains bonded to the substrates involved, despite the effects of any environmental conditions. They also need the right levels of flexibility and elongation capabilities in the event of stress caused by dissimilar substrates with differing thermal coefficients of expansion and elongation.

Made from flexible materials like silicone, polyurethane and acrylics, sealants do have built-in flexibility and ability to handle elongation and expansion, but in many cases an inert elastomeric filler material is included to extend these. Other requirements for sealants include weather, UV and ozone resistance, and a paste-like consistency which will cure to a durable rubbery seal with low shrinkage on application, so that that the seal which fills the gaps is durable.

Adhesives are often also required to take on some of their partner’s qualities and become sealing agents, mainly to ensure the bond it makes when it binds two substrates together will last.  This sealing role usually involves waterproofing the bond, protecting it from loosening because of dynamic loads, and lessening the chances of bonds deteriorating due to oxidation and corrosion.

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