Plastic compounding is a process of mixing synthetic resins with required plastic additives in a certain ratio to prepare a compound (or molding compound) suitable for processing. It is one of the main contents of plastic engineering.

Development and Origin

Plastic compounding can be traced back to the birth of celluloid in 1870 (see plastic processing industry). In 1931, the German company Farben industrialized the production of polyvinyl chloride. The large-scale production and application of polyvinyl chloride promoted the development of plastic compounding technology. Since the production process of soft polyvinyl chloride plastic products evolved from the rubber industry, the compounding of polyvinyl chloride plastics also mostly uses rubber equipment. In the early 1940s, the extrusion compounding method of polyvinyl chloride pellets began to be used. In 1948, Monsanto Company of the United States developed a polyvinyl chloride dry blend compounding method. Since then, with the development of plastic blending, filling, reinforcement and other modification technologies, the compounding technology of various general and engineering plastics has also developed day by day. By the late 1970s, 60% of the world's thermoplastics needed to be processed after compounding. At the same time, the research and development of compounding equipment also developed.

Process

Depending on the different forms of the compounding materials, the plastic compounding process is also different, but the process is similar (see figure), including: ¢Ù Measuring: Accurate weighing of various raw materials. ¢Ú Mixing: In mixing equipment of different forms and structures, the various components are evenly dispersed and mixed. ¢Û Plasticization: Use internal mixers, open mixers or plasticizing extruders (see plastic machinery) to melt and homogenize the mixed components. ¢Ü Separation: Remove volatile components, air and impurities brought in by raw materials. ¢Ý Granulation: If granules are required, various granulators are used to cut them into granules of a certain size and shape.

Detailed introduction

In plastic compounding, in addition to considering the compatibility of the formula and different components, the selection of compounding process and equipment also plays an important role in the quality of the compound. In order to design special compounding materials with precise processing characteristics to meet the requirements of diversified plastic processing and application, plastic compounding has developed from a simple mixing operation to a complex and sophisticated process. In recent years, the development of plastic compounding technology has been committed to improving production efficiency, improving compounding material quality, reducing labor consumption, facilitating operation, and ensuring production safety and environmental hygiene. The plastic compounding process is becoming more continuous, closed, large-scale, high-speed and automated. Automated professional plastic compounding plants controlled by computer programs have appeared. In addition, the deepening of research on mixing mechanisms and the selection of plastic additives and their mechanisms of action is promoting the advancement of plastic compounding technology and equipment.

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