Myth #4: All Structural Adhesives are Epoxies

“Epoxy” is often used as a generic name for adhesives, but epoxies are actually only one of the common chemistry families that make up structural adhesives. Depending on the materials you’re bonding, the assembly process and end-use conditions, a structural adhesive from a different family may be more appropriate. The three main chemistries are epoxy, acrylic and urethane adhesives, while the PUR, instant and anaerobic adhesive families are also good choices in certain situations. 3M offers 20 chemistries and numerous specific products across these families, and we can help find the right option for you.

See page 4 of this PDF (416.34 KB) for enlargment of the 3M Structural Adhesives wheel.

Epoxy adhesives are extremely strong and durable in demanding end-use conditions such as outdoor weathering or chemical exposure. Epoxies show the best resistance to high temperatures, solvents and harsh environments, bond a wide variety of materials, withstand vibrations, impact and fatigue, and are available in a variety of open times.

Acrylic adhesives provide a fast cure rate and bond exceptionally well to low surface energy (LSE) substrates, including most plastics and difficult-to-bond paints and coatings as well as metals that may be somewhat oily. Acrylics are the least sensitive to surface preparation and to off-ratio mixing, and many acrylic adhesives are available in low-odor options.

Urethane adhesives are ideal for creating strong, flexible bonds between dissimilar materials; they bond well to composites, wood, glass and concrete as well as a variety of engineering plastics and some metals. Urethanes have the strength and flexibility to resist shock, vibration and impact loads and are available in a range of process times to suit process needs.

PUR adhesives combine flexibility and the initial speed of a hot melt with the strength of a structural adhesive. PUR adhesives are one-part formulations that require no mixing and rapidly reach handling strength with no need for clamping, They bond well exceptionally well to wood, glass, ceramics and many plastics including nylon, have low to no VOCs and come in a variety of open times to suit process requirements.

Instant adhesives, also known as cyanoacrylates, are one-part adhesives that reach handling strength in seconds. They are excellent for bonding rubber, including EPDM and silicone, and also bond well to common engineering plastics, LSE plastics, metals and wood. Instant adhesive are best suited for small parts assembly.

Anaerobic adhesives, commonly known as threadlockers, are one-part adhesives that cure in the absence of oxygen. They augment the strength of a threaded joint and prevent loosening due to excessive vibration. Threadlockers require no mixing and resist pressure, vibration and galvanic corrosion.