How Do Plastics Change from Masterbatch to Molded Products? (Part One)

Plastic processing is also called plastic molding. It is a process of processing plastics or synthetic resin into plastic products. At present, the manufacturing processes are mainly composed of choosing materials, molding, machining, joining, decoration, and assembly.
 

1. Choosing materials

This is the first step of the plastic's processing. In addition to the polymer, some stabilizers, plasticizers, colorants and other plastic additives need to be added, so that the performance of the processed plastic products will be greatly improved. Also, production costs can be reduced. The polymer and additives are mixed and dispersed into a dry blend. They can also be processed into granules.
 
2. Molding
This is the most critical step in plastic's processing. We need to make various forms of plastic into parts with the required shape. There are many molding methods, and the selection is mainly based on the type of plastic, initial shape, size and shape of the product. If it is a thermoplastic, extrusion, injection molding, calendering molding, blow molding, and thermoforming are generally used; if it is a thermosetting plastic, then compression molding, transfer molding, or injection molding can be used. In addition, there are also castings using liquid monomers or polymers as raw materials.
 
3. Machining
This step can be viewed as an auxiliary process of forming. Some plastic products with accurate dimensions or small quantities can be manufactured based on the processing of metal or wood. The tools and cutting speeds used in machining must conform to the characteristics of plastics.
 

4. Joining

This step is to put the plastic parts together. There are two main methods, that is, welding and bonding. The welding methods are mainly hot air welding, hot melt welding, high-frequency welding, friction welding, ultrasonic welding and so on. The bonding method is done by using adhesives such as the fusing agent, resin solution and hot melt adhesive bonding.
 
5. Decoration
The purpose of this step is to beautify the surface of the plastic product, usually through mechanical modification, such as grinding and polishing; painting is also used, such as coating the surface of the part with paint, covering the surface of the product with a patterned film, etc. There are color painting, such as colored drawing, printing, etc.; there are also metal plating, including vacuum coating, electroplating, and chemical silver plating.
 
6. Assembly
This is the last step in the processing of plastics, that is, combining the processed individual plastic parts to form a complete plastic product.
 
What are the common plastic processing technologies?
1. Injection molding is a method of producing styles for industrial products. Products are usually produced by rubber injection molding and plastic injection molding. Injection molding can also be divided into injection molding compression methods and die casting methods. An injection molding machine is the main molding equipment that uses plastic molding molds to make plastic products with various shapes from thermoplastics or thermosets. Injection molding is achieved through injection molding machines and molds.
 
2. Through the action between the extruder barrel and the screw, the extruded material is heated and plasticized while being pushed forward by the screw, and continuously passed through the die to make various cross-section products or semi-products.
 
3. Blow molding, also called hollow blow molding, is a rapidly developing plastic processing method. The tubular plastic parison obtained by the thermoplastic resin being extruded or injection molded is placed in a split mold while it is hot (or heated to a softened state). After the mold is closed, compressed air is injected into the parison to make the plastic parison expand and cling to the inner wall of the mold. After cooling and demolding, various hollow products are obtained.
 
4. Vacuum molding is a kind of plastic processing technology. The main principle is to heat the explanate plastic hard sheet to soften it, and then use the vacuum to vac-sorb it on the surface of the mold. It is formed after cooling, which can be applied to all walks of life.
 
5. Compression molding, is a process in which powder, granular or fibrous plastic is first placed in the mold cavity at the molding temperature, and then the mold is closed and pressurized to form and solidify. Compression molding can be used for thermosetting plastics, thermoplastics and rubber materials.
 
6. Calendering molding is a process that takes the melted and plasticized thermoplastic through the gap of two or more parallel and counter-rotating rollers, so that the melt is squeezed and stretched by the rollers to become a continuous sheet with certain specifications and dimensions and quality requirements. The product is finally formed by natural cooling. Calendering molding is often used in manufacturing plastic films or sheets.