Why You Should Start Switching to Adhesives Today
The transition from mechanical fasteners to adhesives will often require a period of time for engineers as they test the efficacy and strengths of different adhesives. This trial period will allow engineers to find the best adhesive for each given product.
Finding a supplier already knowledgeable in this area can greatly reduce the time and costs associated with this phase of the project.
Adhesives are now being used in both large and small-scale projects across every industry. An experienced supplier can also offer advice on the best screening tests to perform, as well as testing protocol. This will help the engineer avoid additional expenses or wasted time on adhesives that will not be the best fit for a particular project.
When working with a supplier, it is important to consider several factors in replacing mechanical fasteners with adhesives. Those factors include:
- Assembly: Assembly required could be as simple as attaching trim or a gasket, or as in-depth as a full-surface lamination.
- Substrate: Substrate materials to be bonded is a major consideration because it may require a more flexible adhesive to accommodate differences in movement or thermal expansion.
- Process: Adhesives or tapes can be used in manufacturing processes manually or via automation depending upon part sizes, volume, and other factors.
- End-use: Considering the end-use of a product is key because there may be environmental requirements for the assembly. These can include, but are not limited to, extreme temperature, UV, or chemical resistance.
- Cost: Using adhesives and tapes often reduces labor and process steps, as well as allows less expensive materials to be used, which greatly cuts cost.
Classifying Adhesives
Adhesives can be categorized in several different ways. These categories include form, strength, structural or non-structural, pressure-sensitive, and hybrids.
Form:
Adhesive formats include liquids, pastes, tapes, films, and shaped solids. Each form’s characteristics will play a role in effectiveness and efficacy. Liquids and pastes readily fill voids to improve mechanical adhesion, and some liquids can be sprayed to cover large areas.
Films and tapes provide uniform thickness throughout the joint, as well as immediate bonding. There is also no overflow, dripping, or wasted adhesive. These forms can also be cut to make it easier to bond complex parts or narrow bonding surfaces.
- Strength: Another classification for adhesives in industrial applications is by relative strength. Adhesives that bond through chemical reactions are generally stronger than those that bond through physical changes.
- Structural adhesives: Structural adhesives bond the load-bearing parts of products. Generally, structural strength adhesives reach a minimum of 1,000 psi overlap shear strength. These structural adhesives include epoxies, acrylics, urethanes, cyanoacrylates, and anaerobics.
Epoxy adhesives have the highest strength and temperature resistance. Acrylics bond to the widest variety of substrates. Urethanes are low cost and bond quickly, while cyanoacrylates harden in almost seconds. Anaerobic adhesives cure to tough plastic in the absence of oxygen. - Non-structural adhesives: Unlike structural adhesives, non-structural adhesives create bonds that vary in strength. The adhesives are typically less than 1,000 psi in overlap shear strength and bond materials in cushions, gaskets, insulation. Non-structural adhesives include hot melts, rubber, and contact bond adhesives.
Hot melts flow under heat and quickly form bonds. Rubber adhesives solidify through evaporation of the carrier, while contact bond adhesives usually get rolled, brushed, or sprayed on and left to dry. - Pressure-sensitive adhesives: Pressure sensitive adhesives conform to surface irregularities over time. These adhesives are almost always applied via tapes and they grip immediately to mating surfaces.
- Hybrid adhesives: These materials combine properties of different types of adhesives. Combining properties of adhesives allows for the best solution for each application’s specific needs. For example, curing hot melts are moisture-curing urethanes that apply like a hot melt adhesive but when cooled have bond strength akin to two-part structural adhesives. Likewise, reclosable fasteners combine adhesive and mechanical fastening principles.