At present, the output of general-purpose thermoplastics in the world accounts for almost 80% of the total output of plastics, and China is no exception. These plastics are processed by physical processing techniques, such as extrusion, injection, calendering, etc., that is, plastics are produced by heating, melting and cooling. In the past 20 years, the development of processing technology is very fast, but the tone changed little, but by the one-way type to the combination type development, such as push - pull - blowing, injection stretch blow molding, extrusion, hot extrusion composite molding technology development, from general to special conditions, such as high pressure, high high temperature, vacuum plasma spraying, etc..
The extrusion molding
The thermoplastic resin and various additives are mixed and granulated to be added into the extruder. The material is subjected to mechanical shearing, friction, heating and heating in the barrel, melting and plasticizing it, and pushing it into a compact melt as it rotates forward. The melt is changed into a profile with constant cross section through the filter plate and different molding dies, and the product is cooled and shaped.
The plates, rods, tubes, wires, sheaths, wires, belts, and some of the films we usually see are made in this way. China has been able to produce fine coarse mesh such as fishing, such as large diameter plastic 0.2m diameter pipe, special-shaped profile production buildings can also use, such as plastic doors and windows.
The extrusion molding has the advantages of high production efficiency, simple operation and uniform product quality; the equipment can be big or small, and can be simple, fine, easy to manufacture, easy to put into production, and can be used by one machine for multiple purposes or for comprehensive production. In addition, extrusion machine can also be used in mixing, plasticizing, dehydration, granulation, feeding and other different processes.
The calendering
Roll forming is one of the main molding methods of thermoplastics. The method is mainly to make films and sheet materials. Suitable for rolling thermoplastics, PVC, PE, PP, ABS, CA, VC/EVA and so on.
The injection molding
Injection molding, also known as injection molding, is an injection molding process. Injection molding has the advantages of high production speed, high efficiency, automatic operation, and complex parts. The disadvantage is that the mold costs are high and the cleaning is difficult, so it is not suitable for small batch products to be molded by this method. With this method the molding products: TV shell, shell, semiconductor radio on the electrical connector, knob, coil frame, gear, automobile lampshade, cups, bowls, soap box, bathtub, sandals etc..
At present, injection molding applies to all thermoplastics, and its molding cycle is short, the variety of varieties, shapes can be from simple to complex, the size can be large to small, and the size of products accurate, easy replacement of products.
The blow molding
Blow molding, including blow molding film and blow molding hollow products two.
The foam molding
Plastic foam is made of resin as the main component, containing numerous tiny pores of plastic products, also known as microporous or porous plastic. Modern technology can make almost all thermoplastic and thermosetting resins processed into foam plastics. At present, the resins usually used for making foam plastics are polystyrene, polyvinyl chloride, polyethylene, polyurethane, urea formaldehyde resin and so on.
Foam plastics are classified into soft, hard and semi rigid foams according to the degree of hardness and hardness of the products.
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