Blow molding: Also known as hollow blow molding, a rapidly developing plastic processing method. The tubular plastic billet obtained by extrusion or injection molding of thermoplastic resin is placed in a split mold while it is hot (or heated to a softened state), and compressed air is passed into the billet immediately after the mold is closed, so that the plastic billet is blown and close to the inner wall of the mold, and various hollow products are obtained after cooling and demoulding. The manufacturing process of blow molded film is very similar in principle to that of blow molded hollow products, but it does not use molds, and the molding process of blow molded film is usually included in the extrusion from the perspective of plastic processing technology classification.
When selecting a resin for blow molding, consider MI, density and molecular weight distribution of the resin. Generally speaking, when MI is less than 2, blow molding is better, and the wider the molecular weight distribution, the better the molding performance.
The relationship between rigidity and ESCR varies with density, and the factor that has a greater influence on the rigidity of resin and the adjustment of ESCR performance is density. As the density changes, the rigidity and ESCR performance show the opposite result. Blow molding products are mainly used in containers, so the outer wall of the molded part should have rigidity that can withstand a certain pressure, and has ESCR performance to ensure that the contents will not leak when used for a long time in hot and cold weather.
The density is the factor that has a great influence on the rigidity of resin and the adjustment of ESCR properties. As the density changes, the rigidity and ESCR performance show the opposite result.
