Polyvance R02-01-04-NT Polypropylene Rod 1/8" | 1 lb. | NaturalPolyvance R02 01 04 NT Polypropylene Rod 1 8" 1 lb. Natural Polypropylene is commonly used in the bumpers of import cars, typically in black or gray. This waxy plastic can become "hairy" when sanded at high speed. If you have determined that the plastic you need to weld is polypropylene, this is the welding rod you require. Use this rod with either Polyvance's airless plastic welder or a hot air plastic welder. The black color helps make repairs to