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What is the difference between the blow molding process and the injection molding process?
- Jul 20, 2018 -

Blow molding products are hollow; injection molding has an injection mold, so the molding product will be more than a small part, there will be a process to cut it, but if careful observation can be found;

Injection molding (injection molding) is a method to make thermoplastic or thermosetting plastic moulded in a heating barrel first, and then formed in the cavity of a closed die by a plunger or moving screw.

Injection molding is almost suitable for all thermoplastics. In recent years, injection molding has also been successfully applied to some thermosetting plastics. The molding cycle of injection molding is short (a few seconds to several minutes). The quality of the molded products can be from several grams to dozens of kilograms, and the molding products with complex shape, precise size and metal or non metal insert can be formed once. Therefore, the method is highly adaptable and highly efficient.

Blow molding: by means of gas pressure, the hot parison closed in the mold is blown into hollow products, or a tube mold blank blown to form a tube membrane. The method is mainly used for the manufacture of various packaging containers and tubular membranes.

All the melt index 0.04~1.12 are excellent hollow blow molding materials, such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, thermoplastic polyester, polycarbonate, polyamide, cellulose acetate and polyacetal resin, among which polyethylene is the most used.

(1) injection blow molding: the injection molding process is used to make plastic billets, and then the parison is moved into the blowing mould to blow into hollow products.

(2) extrusion blow molding: first, the plastic is made into a base parison by extrusion, then the blank is moved into the blowing mold and blown into hollow products.

(3) stretching and blowing molding: stretching blow molding is a kind of blow molding of biaxial directional stretching. The method is to stretch the shape first and then stretch to reach the transverse stretch with compressed air. The tensile blow molding can greatly improve the transparency, impact strength, surface hardness and rigidity of the products. It is suitable for the blow molding of polypropylene and polyethylene terephthalate (PETP).

(4) blown film method: a method of forming thermoplastic films. The plastic extrusion method was used to squeeze the plastic into a tube, and then the air that was blown into the tube was expanded to a certain size tube membrane, and then folded and rolled into a double flat film after cooling.