“I am trying to adhere a Polyethylene (PE) foam material onto a Polyethylene (PE) rigid, smooth plastic material. I prep both surfaces with a primer (Loctite 7701) before dispensing the adhesive, which is Loctite’s 4011 cyanoacrylate medical-grade adhesive. The adhesive is anchoring or sticking really well to the PE foam, but not the rigid plastic. They are both PE materials and I am not sure why it would adhere to one and not the other.
Are there different primers that vary in performance?”
One reason why the adhesive might stick better to the foamed Polyethylene (PE) is its larger surface. Due to the holes and grooves, adhesives in general can hold on better and achieve a mechanical lock.
According to the suppliers web site, the primer you are using is recommended for PE. If it is not providing the desired results, you may want to look into another surface treatment method such as plasma or corona, which adds polar groups to the surface and usually results in higher bond strengths.