The plastics we usually use are not pure substances. It is made of many materials. Polymer (or synthetic resin) is the main component of plastics. In addition, in order to improve the properties of plastics, various auxiliary materials such as fillers, lubricants, plasticizers, colorants and stabilizers are added to the polymer to make plastics become plastics with good properties.
Lubricant is used to prevent plastics from sticking to metal moulds in the forming process, so that the surface of plastics is smooth and beautiful. Commonly used lubricants are stearic acid and calcium magnesium salts.
Colorants give plastics a variety of bright and beautiful colors. Organic dyes and inorganic pigments are common colorants.
In order to prevent the photothermal decomposition and destruction of synthetic resins in the process of processing and use and prolong their service life, stabilizers were added to plastics. Stearate and epoxy resin are commonly used.
Plasticizer can improve plasticity and softness of plastics, reduce brittleness and make plastics easy to process. Plasticizers can generally be mixed with resins, non-toxic, odorless, light, heat-stable high boiling point organic compounds, the most commonly used is phthalates. For example, in the production of PVC plastics, soft PVC plastics can be obtained by adding more plasticizers. If no plasticizers are added or fewer plasticizers are added (dosage < 10%), then rigid PVC plastics.
Fillers, also known as fillers, can improve the strength and heat resistance of plastics and reduce costs. For example, adding wood flour to phenolic resin can greatly reduce costs, make phenolic plastics one of the cheapest plastics, and significantly improve mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former such as wood flour, rags, paper and various fabric fibers, the latter such as glass fiber, asbestos, diatomite, carbon black and so on.
6. Synthetic resins
合成树脂是塑料中最重要的成分，其在塑料中的含量一般为40% ~ 100%。树脂通常被认为是塑料的同义词，因为它的高含量，因为树脂的性质往往决定塑料的性质。例如，聚氯乙烯树脂与聚氯乙烯塑料、酚醛树脂与酚醛塑料混淆。实际上树脂和塑料是两个不同的概念。树脂是一种原始聚合物，不仅用于制造塑料，还用于涂料、粘合剂和合成纤维。然而，大多数塑料除了其主要成分树脂外，还需要添加其他物质。
Synthetic resin is the most important component in plastics, and its content in plastics is generally 40%-100%. Resins are often considered synonymous with plastics because of their high content, because the properties of resins often determine the properties of plastics. For example, polyvinyl chloride resin is confused with polyvinyl chloride plastics, phenolic resin and phenolic plastics. In fact, resins and plastics are two different concepts. Resin is a primitive polymer used not only in the manufacture of plastics, but also in coatings, adhesives and synthetic fibers. However, most plastics need to add other substances besides resins, which are the main component.