blow molding, a rapidly developing plastic processing method

A tubular plastic parison obtained by extrusion or injection molding of a thermoplastic resin is heated (or heated to a softened state) and placed in a split mold. Immediately after closing the mold, compressed air is blown into the parison to blow the plastic parison. Swelling and close to the inner wall of the mold, after cooling off the mold, that is, all kinds of hollow products. The blown film manufacturing process is similar in principle to the blow molding of the hollow product, but it does not use a mold. From the perspective of the plastic processing technology classification, the blown film forming process is usually included in the extrusion. The blow molding process began during the Second World War to produce low-density polyethylene vials. In the late 1950s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology was widely used. The volume of hollow containers can reach several thousand liters, and some productions have been computer controlled. Suitable plastics for blow molding are polyethylene, polyvinyl chloride, polypropylene, polyester, etc. The resulting empty containers are widely used as industrial packaging containers.