Thermoplastic polyolefins like polyethylene and polypropylene, and polyolefin elastomers such as EPDM rubber are notoriously difficult to join. Solvent welding does not produce strong bonds as polyolefins normally have excellent resistance to solvents. Polyolefins have very low surface energies so adhesives do not wet-out the surface well without some form of surface treatment. Surface treatments such as corona, flame, or plasma treating add costs to manufacturing.
Cyanoacrylates and acrylics are the best polyolefin bonding adhesives.
Pretreat the polyolefin with Permabond Polyolefin Primer (POP) and bond with Permabond Cyanoacrylate. This combination will generally create a bond stronger than the polypropylene or polyethylene substrate in shear however, impact strength is low. POP and cyanoacrylate is a fast, effective solution for many applications. Cyanoacrylate and POP will form bonds with good shear strength and good resistance to non-polar solvents (ex. motor oil, gasoline).
Other applications which require more impact strength or more resistance to water and other polar solvents are better handled with Permabond TA46XX series polyolefin bonding adhesives.
These 1:1 mix acrylics can be dispensed from a dual cartridge so no mixing is needed. TA4605 achieves handling strength in 25 minutes and TA4610 has a longer pot life so handling strength is delayed to 50 minutes. Permabond TA4611 is lower viscosity and has no induced gap. TA4631 also has not induced gap and is a low odor version.
There is no need for a primer or surface treatment (such as flame, corona or plasma). They bond a wide range of substrates and even have some strength in bonding PTFE and silicone rubber.
For more information on these products or to discuss your polyolefin adhesive needs, contact Permabond.
Picture shows polypropylene test piece bonded with TA4610 – the lap shear stretches and distorts but the bond is still intact.