I'm with SJones, the approx surface energy of LDPE at 30 dynes/cm is too low for any durable bond. You would just be molding the material around the LDPE. Polyurethanes may be as low as 38 dynes/cm but epoxies are around 45 dynes/cm. A hybrid would be somewhere in between. DuPont did research on Teflon years ago and determined the surface energy of an adhesive should be 10 dynes/cm "lower" than the substrate surface energy to create a durable bond. This isn't really possible for some materials and research has shown that pressure sensitive adhesives perform better on low surface energy substrates. Their are surface treatment to elevate the surface energy of the substrate. Those should be discussed with the 3LPE supplier.
Depending on what you are trying to do, you might consider using a tape to bond to the 3LPE and then use the medium of the tape as the bonding surface for the hybrid adhesive. 3M and maybe Henkle are good sources. Looking at the SP-2888, I think the dynes/cm will probably be more in line with an epoxy than a polyurethane. If what you are really looking for is a transition between the coating & the 3LPE, then maybe all you really need if a specialty tape.