Plastic molding methods

Plastic molding refers to the process of making final plastic products from polymers made of synthetic resins.

Processing methods (usually referred to as primary processing of plastics) include compression molding (extrusion molding), extrusion molding (extrusion molding), injection molding (injection molding), blow molding (hollow molding), calendering, foaming, and vacuum forming.

(1) Compression molding is also called film molding or compression molding. Compression is mainly used for the molding of thermosetting plastics such as phenolic resin, urea-formaldehyde resin, and unsaturated polyester resin.

(2) Extrusion molding is also called extrusion molding. It is a method in which an extruder (extruder) continuously passes heated resin through a mold to extrude the desired product. Extrusion is sometimes also used for the molding of thermosetting plastics and foam plastics. The advantages of extrusion are that it can extrude products of various shapes, has high production efficiency, and can be automated and continuously produced; the disadvantages are that thermosetting plastics cannot be widely processed by this method, and the product size is prone to deviation.

(3) Injection molding is also called injection molding. Injection molding is a method of injecting thermoplastic melt into a mold under high pressure using an injection molding machine (symmetrical injection molding machine) to obtain a product after cooling and solidification. Injection molding is also used for the molding of thermosetting plastics and foam plastics. The advantages of injection molding are fast production speed, high efficiency, automated operation, and the ability to mold complex parts, which is particularly suitable for mass production; the disadvantages are high equipment and mold costs, and difficulty in cleaning the injection molding machine.

(4) Blow molding is also called hollow blow molding or hollow molding. = Blow molding is a method of using compressed air pressure to blow the hot resin parison closed in the mold into a central product. Blow molding includes two methods: blow molding film and blow molding hollow products. Blow molding can produce film products, various plastic hollow bottles, barrels and pots, and children's toys.

(5) Calendering is a molding method in which the material is processed into a film or sheet through the gap between two or more oppositely rotating calender rollers of a calender after the desired treatment (kneading, filtering, etc.) of the reduced value and various additives, and then peeled off from the calender roller and cooled and shaped. Calendering is a molding method mainly used for polyvinyl chloride resin, and can be used to manufacture films, sheets, plates, artificial leather, floor tiles and other products.

(6) Foaming molding. The process of adding appropriate foaming agents to foaming materials (PVC, PE, PS, etc.) to make the plastic have a microporous structure. Almost all thermosetting and thermoplastic plastics can be made into foam plastics. According to the pore structure, it is divided into open-cell foam plastics (most of the pores are interconnected) and closed-cell foam plastics (most of the pores are separated from each other), which is mainly determined by the manufacturing method (chemical foaming, physical foaming and mechanical foaming).

(7) Blister products are made by heating and softening flat plastic sheets, adsorbing them to the mold surface with vacuum, and then cooling them into shape. Blister products are widely used, mainly for packaging of various products, trays, etc.