Plastic welding is limited to thermoplastic welding because only thermoplastics can be melted or softened while they are heated, while thermosetting plastics cannot be softened and remelted while they are heated.Hot air welding oxyacetylene similar to metal, but the latter with the former fire hot air heating. Hot gas welding process, the welding torch from the hot gas stream (typically 200 to 300 degrees Celsius temperature, flow rate of 15 ~ 60L/min) and the filler rod and welding pieces of the heating surface, when the material softening reached sticky state, filling rod continuous pressure into the weld. The filling bar material is the same as that of the base metal, usually round (about 3mm in diameter), and is welded by multiple bead welding. One drawback of the round filling rod is that the hollow bubbles are easily entrapped in the weld during the multi pass process, resulting in lower strength. This problem can be solved by using a triangular section welded rod. Typical materials for hot air welding include polyvinyl chloride, polyethylene, polypropylene, plexiglass, polycarbonate, POM, polystyrene, nylon, ABS and so on. The main advantage of hot gas welding is adaptive (flexibility), portable equipment and processing of large, complex parts can be simple. Hot air welding is suitable for irregular structures, but it is slow and the quality of welding depends largely on the skill of the operator. Therefore, it is seldom used in mass production, but it is suitable for repair operation.
Bonding can achieve good performance and good quality joints, but it is difficult to operate. It needs careful preparation of joints and surfaces, and it is very slow and unsuitable for mass production. The welding is economical, simple, fast and reliable, and can form static strength close to the parent material. Therefore, it is suitable for mass production, and has gained more and more extensive application in the automobile industry. The level of plastic welding technology has become one of the marks to measure the level of automobile production technology and new material development.
Plastic connection is the key link of its extensive application. Plastics can be connected by mechanical fastening, bonding, or welding. Fastening, fast connection, suitable for all plastics, but high cost, will produce stress concentration, can not form sealed joints or get the appropriate performance.
