I was surfing around trying to find a glue for coroplast as PP is notoriously difficult to glue.
These guys claim to have a glue (primer/activator + glue) for PE and PP (coroplast / corplast) :
PASCO - SHOP - Prime & Pepp
Hit the "More" link (next to "add to cart") for more info on both products.
I haven't used it, and I don't know wether anyone on here has.
I've also found someone reporting that SIKAFLEX-11FC from Sika.com works.