It goes without saying that if you are bonding plastics use a plastic adhesive and if your bonding metal, an adhesive for metal. It gets more complicated when you want to choose industrial adhesives to join dissimilar substrates.
Two HUGE categories here – there are likely an infinite number of combinations of plastic to metal. Some plastics easily bond, while others require specialty adhesives. Most metals are readily bonded provided the surface isn’t oxidized (think rust and corrosion.) So let’s go worst case scenario here and pick a tough to bond plastic and a tough to bond metal.
PTFE (also known as Teflon® and polytetrafluoroethylene) is one of the most difficult to bond plastics. The coefficient of friction is the 3rd lowest known. As slippery as it is, it is used to line containers, coat processing equipment, and for slides to protect piping and other metals.
Again a variety of adhesives readily bond most metals. Stainless steel is relatively easy to bond, but depending on the surface condition. Mirror finish stainless steel can have very low surface energy and provide difficult. Automated means of abrading the surface can generate heat which might cause a surface change decreasing the adhesion of adhesives to the stainless steel.
If treatment is needed to obtain a high strength bond to mirror finish stainless steel, sand blasting is recommended to roughen up the surface without generating heat.
In this scenario, there are few adhesives that offer any adhesion to PTFE. Options include either a cyanoacrylate along with POP primer or a structural acrylic like Permabond TA4610 or.
Generally, if a designer chose SS and PTFE – the item likely needs to resist abrasion, impact, chemicals, temperature, etc.…
Standard cyanoacrylates are brittle and have low impact resistance. They have good resistance to non-polar solvents and withstand 180F. Bond strength on
Permabond structural acrylics like TA4610 have good adhesion to PTFE with no primer needed. They also bond stainless steel (over 1000 psi shear strength). Standard epoxies will have double that strength to stainless but virtually no strength on PTFE. In the following image, PTFE bonded with TA4610 stretches and ultimately fails before the bond.
Bonding dissimilar substrates can be challenging but with a good understanding of what the industrial adhesives bond needs to withstand it is generally possible. Questions about bonding dissimilar materials – contact Permabond for a recommendation.
Teflon is a registered trademark of the Chemours company
