It's important to identify the plastic you're welding as only like plastics can be joined. The simplest way is by performing a burn test.
Take a small sliver or shaving of the material to be welded and light it with a flame, observe and smell the smoke. Most commonly:
See our Plastics Identification Flow Chart for an expanded listing of plastics and their properties.
Recommended Further Reading
Originally published: 9/19/2014