On 29 July, 22:58, Jan Wysocki
wrote:

specifically state that they won't bond to polypropylene.

Polypropylene is about as awkward as polyethylene. There are some
specific adhesives for them, but even these aren't wonderful. I'd go
with screws.

For some large pieces of PP, it's easier to hot weld it. This is quite
easy if you have a hot-air welding gun - people who do car bodywork
do.