The plastics that we usually use is not a pure substance. It is made by the preparation of many materials, in which the high polymer (or synthetic resin) is its main part. In addition, in order to enhance the performance of plastics, a variety of auxiliary materials should also be additional in the polymer, such as fillers, plasticizers, lubricants, stabilizers, coloring agents, and so on, so as to make the plastics have good performance.
First, synthetic resin
Synthetic resin is the main part of plastics. The general content of synthetic resin in plastics is from 40% to 100%. Because of its large content, the character of synthetic resin often determines the character of the plastics, so people often take resin as a synonym of plastics. In fact, resin and plastics are two different concepts. Resin is a raw polymer which has not been processed. While for most plastics, besides the resin as its main part, there are also some other substances.
Fillers can increase the strength and heat-resistant quality of the plastics, in addition as lower the cost. For example, adding wood flour into phenolic resin can greatly reduce the cost, which makes the phenolic plastic as one of the cheapest plastics. At the same time, it can also considerably enhance the mechanical strength. Fillers can be divided into organic filler and inorganic filler, with the former as wood flour, rags, paper and all kinds of textile fibers, and the latter as glass fibers, diatomaceous earth, asbestos, and carbon black.
Plasticizers can increase the plasticity and flexibility of the plastics, reduce brittleness, and make the plastics easy to be processed and molded. Plasticizers are generally organic compounds with high boiling point, miscible with the resin, non-toxic, odorless, and stable to light and heat. The commonly used plasticizers include phthalates, benzophenone, and so on.
In order to prevent the decomposition and damage of synthetic resin caused by light and heat, and to extend its service life, it is necessary to add stabilizers in plastics. The commonly used stabilizers include stearate, epoxy resin and so on.
Fifth, coloring agents
Coloring agents can provide the plastics with various bright and beautiful colors. Organic dyes and inorganic pigments are often used as coloring agent.
In addition to the above additives, other additives can also be additional in plastics, such as lubricants, flame retardants, blowing agents, antistatic agents, and so on, so as to meet different operating requirements.