Hot Plate Welding Materials

When contemplating use of hot plate welding, a critical consideration is the thermoplastic material to be joined. Generally, one would want to join materials with relatively low melting temperatures, low thermal conductivity, a good spread between the melting and the degradation temperatures, relatively high viscousity when melted, and resistance to interaction with oxygen when melted. If it sounds like this list eliminates a lot of materials, it probably does, but it also includes a lot of materials. Materials with reinforcements and fillers complicate matters and may be better suited to another process. The reason to avoid hot plate welding filled or reinforced materials is the potential for buildup of a residue of filler or reinforcement on the hot plates. This tends to become more of a problem the more parts are run and requires frequent scrubbing or scraping of the plates. This plate cleaning can be relatively easily automated if the plates are planar, but can be complicated and expensive if the plates have complex geometry. Materials that work well with hot plate welding include olefins like polyethylene and polypropylene, fluoropolymers, polystyrene, polymethyl-methacrylate, and acrilinitrile-butadiene-styrene. Materials to avoid hot plate welding include polyamid, polyvinylchloride, and almost all of the very high temperature thermoplastics. Depending on the application, polycarbonate can be hot plate welded but its relatively high melt temperature and especially its relatively high thermal conductivity can make it difficult to work with. High material lubricity is not an issue for hot plate welding and therefore recommends it over frictional methods. Hot plate welding also handles complex joint geometries pretty well, which also recommends it over frictional processes for these materials. Part warp issues must be minimized by fixturing and can be an issue with some assemblies, especially larger assemblies.