The plastic processing method in which the plastic is plasticized in the heating barrel of the injection molding machine and injected into the cavity of the closed mold by the plunger or the reciprocating screw to form the product. This method can process products with complex shapes, precise dimensions or with inserts, and has high production efficiency. Most thermoplastics and some thermosets such as phenolics can be processed this way. The material used for injection molding must have good fluidity in order to fill the mold cavity to obtain the product. Since the 1970s, there has been a type of injection molding with chemical reaction, called reaction injection molding, which has developed rapidly.