1. Injection molding
Among all plastic processing methods, injection molding is the most widely used. The method is that the thermoplastic or thermosetting plastic is introduced into the heating barrel of the injection molding machine, and after it is completely melted, the pressure of the plunger or screw generates heat and frictional heat, which is injected into the cavity of the closed mold to solidify After that, PMMA plastic raw materials, and then open the mold to take out the finished product. This processing technology derives other methods due to material, mechanical design and product requirements, such as insert molding of pre-embedded metal parts, multi-color and mixed-color injection molding, injection molding of structural foaming, and gas assisted injection molding. Injection molding), coinjection, hollow injection molding and reactive injection molding (RIM) using liquid monomer or liquid prepolymer as raw materials.
2. Extrusion processing (extrusion)
The thermoplastic material is heated and pressurized in an extruder, and then extruded with a screw. The cross-sectional shape of the extruded product is determined by the die head, which can be rod, tube, flat plate, special shape, etc. Others such as blown film extrusion, extrusion hollow forming, calendering processing, extrusion coating and mixing and pelletizing are all used in the first half of the extruder. Nowadays, the popular trend is co-extrusion processing to produce multi-layer high-functional products.
3. Compression molding
This is one of the thermosetting plastic forming methods. After the thermosetting resin is preheated, the PMMA plastic material is used. Place it in an open cavity, apply heat and pressure after closing the mold until the material hardens. Phenolic resins, melamine resins and urea-formaldehyde resins are commonly formed by this method. The finished products are: home appliance housings, parts, gears, furniture and tableware, etc.
4. Blow molding
The method is to first extrude the thermoplastic from the die of the extruder into a thin tube, which is called a parison, then close the mold, blow air, and then form. The application of this method has become more and more extensive, such as the automobile industry, the materials used have also changed from traditional PE, PP, PVC, PET, etc. to high-performance engineering plastics. The advantage is that it is convenient to manufacture large-shaped products and one-time forming, but the disadvantage is that it is difficult to control the various parts of the plastic product. 5. Rotational molding
Inject the powder or liquid molding material at room temperature into the rotary mold, use heating and centrifugal force to spread the resin evenly on the mold wall, and cool down to obtain a hollow molded product. This method is most suitable for forming large objects, but the disadvantage is that it is difficult to control the thickness.
6. Blown film estursion
There are two general methods of manufacturing films:
(a) T-die method. (b) Ring-die method. (a) T-die method is flat film extrusion, and the thickness of the film produced is more uniform than that of ring die method. Due to the larger pulling force in the drawing direction, the longitudinal strength is much greater than the lateral strength, so many have used biaxial stretching methods to make films. (b) Blown film extrusion is the operation method of ring die, and the molten glue is extruded The tube film is blown with air through the ring mold, and then cooled to form a glue film. Polyolefin plastics are often used to manufacture various garbage bags, shrink films and food packaging films. The current advanced packaging film is the use of co-extrusion method to produce multilayer film.