Extrusion molding is a high-efficiency, continuous, low-cost, wide-format molding process. It is an early technology in the processing of polymer materials. After more than 100 years of development, extrusion molding is in the field of polymer processing. It has the largest variety, the most change, the high productivity, the adaptability, the wide range of uses, and the largest proportion of production. Extrusion is one of the most important forms of plastic material processing. It is suitable for most plastic materials except some thermosetting plastics.
About 50% of thermoplastic products are extruded and used in large quantities. The molding of chemical fibers and thermoplastic elastomers and rubber products; the extrusion molding method can produce various types of continuous products such as pipes, bars, sheet materials, profiles, wire and cable sheaths, monofilaments, etc., and can also be used Mixing, plasticizing, granulating, coloring, and blending modification of polymer materials. Further, based on extrusion molding, extrusion-blown, stretch-stretching, etc. extrusion-blow molding techniques and tenter forming techniques are important methods for producing films and hollow products.
Extrusion Molding, also known as extrusion molding or extrusion molding, mainly refers to the extrusion of a screw or a plunger, so that the heated molten polymer material is forced by the pressure to push through the die. Formed into a forming process with a constant profile continuous profile. The extrusion process mainly includes processes such as feeding, melt plasticizing, extrusion molding, setting and cooling. The extrusion process can be divided into two stages: the first stage is to plasticize the solid plastic (ie, become a viscous fluid) and pass it through a specially shaped die under pressure to become a continuous section with a similar shape to the die shape. The second stage is to use a suitable method to cause the extruded continuum to lose its plastic state and become a solid to obtain the desired product.
According to the plastic plasticizing method, the extrusion process can be divided into dry method and wet method. The plasticization of the dry process is to turn the plastic into a melt by heating, and the plasticizing and pressurization can be carried out in the same equipment. The shaping treatment is only a simple cooling. The plasticization of the wet method is to fully soften the plastic with a solvent. Therefore, plasticization and pressurization must be divided into two separate processes, and the shaping treatment must be carried out with a more troublesome solvent, and the recovery of the solvent must also be considered. Although wet extrusion has advantages in uniform plasticization and avoiding excessive heating of plastics, its application is limited to the extrusion of nitrocellulose and a small number of cellulose acetate plastics based on the above disadvantages.
