How to glue polypropylene?

Polypropylene PP R#5 is highly resistant to solvents, thus it cannot be glued in the same way that PVC can, wherein the surface is prepped using a solvent primer. It can only be joined or ultra-sonicly welded. A workaround exists utilizing a thermal adhesion process to treat the surface with a thin film of another more suitable plastic. One such company is listed below.

For the enthusiast, I recommend abrading the surface of both objects with a coarse wood file before using 2 part epoxy to form a mechanical bond. The two surfaces should be clamped together or placed under a large weight as this will create a thinner bonding layer further increasing sheer strength. Use lots though, and wipe up the excess which is pressed out. A flat rubber mat such as a mouse pad or rubber from a holy innertube placed between the objects and the weight or clamped surfaces will ensure more uniform compression. This is a new skill that takes practice, so do a few test pieces before working on your final product.

CAUTION: Do not use a heat source at any time while using epoxy or solvents as there is a risk of fire or explosion. Always use solvents in a well ventilated area free from any electrical device which could cause a spark.

http://www.fluoroseal.com/adhesion.html

http://www.phillipbeynon.com