Many seeking an adhesive for a construction or engineering project are taken aback by the breadth of characteristics they need to consider.
Specialist manufacturers list thousands of adhesive products, each with a unique selection of properties. You may need to input impact and shear forces, temperature profiles, reversibility, setting times, the mix of substrates, chemical reactivity, toxicity, viscosity, expansion tolerances, light and moisture sensitivity, and a host of other factors you never thought about before. When you’ve whittled it to one, there’s a good chance it isn’t available at the right price.
An alternative may be an adhesive with a wide range of applications. To be sure, you’ll need to consider some of the mission-critical factors.
To add strength to bolts or thread-assembled components adhesive must flow evenly into the grooves, give plenty of time for assembly, and cure in the absence of air or water. Threadlockers suited for small bolts are different from those used on large parts,like bicycle cranks. They have varying torque, shear and impact strength depending on whether you’ll ever want to free them again for access or replacement.
In an age of environmental and health and safety regulation, can you procure approvals for consumer and workforce safety? This article on assessing the environmental impact of adhesives gives more information – http://www.adhesives.org/adhesives-sealants/adhesives-sealants-overview/health-safety/environmental-protection. If an adhesive’s already approved for public marketing it will save you a lot of hassle.
Some products only bond similar or absorbent materials together, others bond a variety. A metal bonding adhesive that grips on steel may not hold on aluminium. When different metals are involved consider the desirability, or otherwise, of insulating them from each other chemically, thermally or electrically. If the parts expand differently with heat the adhesive may need to conduct or flex so this rules out most epoxies.
The number of good quality general adhesives that work with a range of metals and have safety approval is very limited, but there’s news about a new one here http://www.ct1ltd.com/en/metal-to-metal-adhesive.html.
Adhesives are often better than welding because they distribute stress more efficiently across the joint if carefully applied. On a production line how will you check? If this is an issue, think about glues that fluoresce under a UV lamp so that bonds can be quality controlled.