It is possible to glue plastic to plastic, but standard craft glue is unlikely to provide a strong seal. While different types of glue have differing properties, superglue causes chemical reactions in plastic, so using it can damage products and might be dangerous.
One reason plastic is difficult to glue is that it has smooth sides. Glue works better when it can soak into the material or fill small ridges. Teflon, in particular, is notorious for being difficult to glue, so consumers should consider other materials if parts need to be glued together. While hot glue doesn't produce the strongest seals, it's easy to peel off of plastic, making it a good choice for temporary adhesion.