“Adhesive” can be synonymous with “glue,” but structural adhesives are much different than ordinary hardware store products. Structural adhesives are engineered to form bonds that can support loads (via load-bearing joints) and are formulated to improve manufacturing processes and final products for a variety of composite, metal and plastic assemblies.
Structural adhesives are thermoset polymers, commonly available in three main types, or chemistries: acrylic adhesives, epoxy adhesives and urethane adhesives. They will not melt or change with environmental exposure, temperature or time.
There are three methods by which structural adhesives accomplish bonding:
- Chemical - The adhesive and substrate form chemical bonds.
- Mechanical - The adhesive fills imperfections (voids, pores, scratches, etc.) in the substrate surface.
- Diffusion or Adsorption - The adhesive diffuses into the substrate at the molecular level.
Another important characteristic of adhesives is “wetting,” or the ability of an adhesive to maintain intimate contact with the surfaces to be bonded.
Where are adhesives used?
Some industries are seeing widespread adoption of structural adhesives to replace welds, rivets and traditional fasteners. The smooth finish achieved using an adhesive offers improved aesthetics compared to having visible mechanical fasteners. By reducing assembly time, adhesives also increase throughput and result in overall cost savings.
Manufacturers adopting adhesives are using them for:
- Heavy duty trucks
- Service trucks
- Auto bodies
- Architectural cladding
- Heavy duty equipment
- Other manufactured items
Depending on the application, any one of the three adhesive chemistries may be an appropriate choice. Upcoming installments of our blog series “Beyond Ordinary Glue” will examine each chemistry’s qualities in-depth. Learn about Acrylic Adhesives in Part 2. You can also find out more by checking out our adhesive best practices.