Because power tool manufacturers face many challenges in building strong, reliable tools that can withstand the elements and the operators, it is no wonder they are continually in search of the strongest adhesive. The use of adhesives in place of other joining methods solves many of those challenges. Let’s drill into why.
Lighter tools – Adhesive bonding in place of mechanical fasteners allows for lighter materials to be used while increasing the overall strength of the tool.
Efficient process – Adhesive bonding in place of welding yields significant time and labor cost savings. Joining with fasteners is another option, but a threadlocker is required in order to prevent vibration loosening.
Weather resistance – Adhesives can seal as well as join, which can extend the life of power tools.
Vibration resistance – Whether it is threadlocking a fastener or bonding two components together, adhesives unitize those pieces, preventing them from rattling against each other. This also helps keeps noise levels down.
Optimize design – Advances in adhesive technologies provide solutions for bonding the high strength, robust, low surface energy plastics that are common in tool manufacturing. The design freedom adhesives provide engineers permits them to use the best materials for each component.
There are a variety of adhesives for metal bonding. Depending on the type of metal, the surface treatment, the type of strength required, any number of adhesives could be considered the strongest adhesive for that particular application. Structural adhesives include one or two component epoxies, toughened acrylics, and many more. So which is the strongest adhesive? For purposes of comparison, we’ll look at shear strength to steel.
It’s likely that the strongest adhesive bond between two pieces of steel will be a single component epoxy. Strengths can vary by product, but many achieve 4000(28 MPa) to 6000 psi (41 MPa). They are not appropriate for every application as they do require heat curing. A typical cure cycle might be either 130°C (266°F) for 75 minutes or 170°C (338°F) for 40 minutes.
Two-component epoxies generally provide up to 3000 psi (21 MPa). Structural acrylic adhesives provide from 2000 to over 5000 psi (14 to 35 MPa) depending upon the type and grade. Structural acrylic adhesives are available in a few different varieties. There are two component acrylics that can be applied with a static mix nozzle similar to two-component epoxies as well as two-component acrylics which can be applied with one bead on top of the other. Another metal bonding option is to apply an activator to one surface and the adhesive to the other. There are also single component acrylics that do not require an activator when used on metals – however, these take longer to achieve handling strength.
Where speed of cure and strength are required, No Mix Surface Activated Acrylics are preferred as handling strength can be achieved in a few minutes.
More speed needed? Methyl cyanoacrylates exceed 4000 psi (30 MPa) shear strength on steel and achieve handling strength in under 15 seconds – however – they won’t provide the high impact and peel strength of the structural epoxies and acrylics.
The comparisons above were for steel – other metals may provide different strength comparisons.
This question isn’t as easy to answer because each plastic has different bondability. For example, when bonding polycarbonate, substrate failure can be achieved before bond failure with a number of adhesive types. Low surface energy plastics like polypropylene and polyethylene provide excellent properties designers seek – but they are difficult to bond. If we look at low surface energy plastics, there are really only two viable plastic adhesive options – either use a cyanoacrylate after treating with POP (Polyolefin Primer) or specialty structural acrylics like Permabond TA4610.
Here is a look at a few of the applications.
For information on bonding metals, plastics, metals to plastics, or any other substrate, please contact Permabond.