The best glue for polypropylene plastics is JB Weld's "PlasticWeld," according to a test conducted by Craftech Industries. Another glue that works on polypropylene is All Purpose Amazing Goop.
The PlasticWeld glue spreads easily to create gap-free bonds between materials. These bonds result in very strong adhesion because of the absence of air spaces between the two materials. PlasticWeld is a two-part epoxy with two active ingredients (Epichlorohydrin and Bisphenol A) and must be mixed in equal amounts to obtain the final adhesion. After the product is applied, it sets quickly, typically within an hour. All Purpose Amazing Goop, on the other hand, takes approximately two hours to set.
Avoid using Super Glue products on acrylic plastics. A chemical reaction commonly occurs, and the glue burns into the plastic.