Blow molding is the forming of a hollow object by inflating or blowing a thermoplastic molten tube called a “parison” in the shape of a mold cavity. The process consists of extruding or “dropping” a parison on which female mold halves are closed. The female mold halves contain the shape of the product to be produced.
Blow molding covers three main thermoplastic processes: extrusion blow molding, stretch blow molding, and injection blow molding. Extrusion blow molding is the largest of the three, followed by stretch blow molding and injection blow molding. The total blow molding industry is growing approximately 3–5% annually and will continue to grow at this rate.