If it is challenging to adhere to a material due to its low surface energy, it is very critical to choose the correct adhesive to bond that material. There are various ways to increase the surface energy of a material, improving the ability to bond. Here are several different ways to modify surface energy.
The ability of a liquid to chemically interact at the surface can be improved with primers or adhesion promoters. Primers work by adding a monolayer or thin coating of a functional material to the surface. Primers are chemically designed so that one end of the molecules bond very well to low-surface-energy materials while the free end bonds very well to adhesives.
Although we just spent a great deal of time understanding the intricacies of surface energy of materials, in reality, a material to be bonded will arrive with a surface that has been contaminated. This can include dust, oil, grease, fingerprints or any other debris capable of winding up on a surface.
Clean surface allows for maximum wet out and surface contact potential
A contaminated surface inhibits surface contact and wet out potential
It is very often necessary to thoroughly clean material prior to bonding to guarantee the adhesive is making proper contact. There are a few methods to do this:
There are times when cleaning alone is not capable of removing the contaminants on the surface of a material. Injection-molded plastics may contain traces of mold release agents that are designed to resist many solvents. Oxide layers of metals (e.g. rusted iron) are “bonded” to the surface and cannot be removed by solvent cleaning alone. Some industrial oils are resistant to solvents and chemicals with the goal of keeping a metal surface safe from harm during transit.
To prepare a surface adequately for bonding, it may be necessary to add an abrasion step to the process.
1. Clean first – a first round of cleaning can remove much of the contamination present and will prevent debris from smearing during abrasion.
2. Abrade – abrasion with standard abrasive paper or non-woven abrasive pads can remove the contaminated surface and provide roughness.
3. Clean – final cleaning removes any debris left over from abrasion and provides the new, clean surface for bonding.
Need help finding the right product for your project? Contact us if you need product, technical or application advice or want to collaborate with a 3M technical specialist, or give us a call at 1-800-831-0658.
Need help finding the right product for your project? Contact us if you need product, technical or application advice or want to collaborate with a 3M technical specialist, or give us a call at 1-800-831-0658.