In addition to polymers, raw materials used in plastics processing are generally added with various plastic additives (such as stabilizers, plasticizers, colorants, lubricants, reinforcing agents, and fillers, etc.) to improve the molding process and the use of products Performance or reduce the cost of products. Additives and polymers are mixed and uniformly dispersed into powder, also known as dry blends. Sometimes the powder needs to be plasticized and processed into pellets. Such powders and pellets are collectively referred to as batch materials or molding compounds. The key link in plastic processing. Various forms of plastics (powders, pellets, solutions or dispersions) are made into products or blanks of desired shapes. There are as many as thirty kinds of molding methods. Its choice is mainly determined by the type of plastic (thermoplastic or thermosetting), the initial form, and the shape and size of the product. The commonly used methods for processing thermoplastics include extrusion, injection molding, calendering, blow molding and thermoforming. The processing of thermoset plastics generally uses compression molding, transfer molding, and injection molding. Laminating, molding, and thermoforming are forming plastics on a flat surface. The above-mentioned plastic processing methods can all be used for rubber processing. In addition, there are castings using liquid monomers or polymers as raw materials. Among these methods, extrusion and injection molding are the most used, and they are also the most basic molding methods.
There are welding and bonding methods to join plastic parts. The welding method is hot air welding using welding rods, hot melt welding using hot poles, and high-frequency welding, friction welding, induction welding, ultrasonic welding, etc. The bonding method can be divided into flux, resin solution and hot melt adhesive bonding according to the adhesive used. The operation of assembling the finished plastic parts into a complete product by means of bonding, welding, and mechanical connection. For example: plastic profiles are assembled into plastic window frames and plastic doors after sawing, welding, drilling and other steps. Borrowing metal and wood processing methods to manufacture plastic products with very precise dimensions or small quantities can also be used as an auxiliary process for forming, such as sawing of extruded profiles. Since the performance of plastic is different from that of metal and wood, plastic has poor thermal conductivity, low thermal expansion coefficient and low elastic modulus. When the clamp or tool is pressed too much, it is easy to cause deformation, and it is easy to melt when heated and easy to adhere to the tool on. Therefore, when plastics are machined, the tools used and the corresponding cutting speeds must be adapted to the characteristics of the plastics. Commonly used mechanical processing methods include sawing, shearing, punching, turning, planing, drilling, grinding, polishing, thread processing and so on. In addition, plastics can also be cut, punched and welded by laser. Surface modification is to beautify the surface of plastic products, usually including: mechanical modification, that is, using files, grinding, polishing and other processes to remove burrs, burrs, and size correction on the parts; finishing, including coating the surface of the parts with paint, and using solvents To brighten the surface, use patterned film to cover the surface of the product, etc.; apply color, including color painting, printing and hot stamping; metal plating, including vacuum coating, electroplating, and chemical silver plating. Hot stamping is to transfer the colored aluminum foil layer (or other patterned film layer) on the hot stamping film to the part under heating and pressure. Many household appliances, construction products, daily necessities, etc. use this method to obtain patterns such as metallic luster or wood grain.