When plastics are compounded, a small amount of chemical substances are added to synthetic resins or their compounding materials to improve the molding process or impart certain properties to the products. Such substances are dispersed in the synthetic resin or its compound and do not affect the molecular structure of the synthetic resin.

The main requirements for plastic additives are: high efficiency: they can effectively perform their due functions in plastic processing and applications. The selection of additives should be based on the comprehensive performance requirements of the compound.

• Compatibility: It can be better compatible with synthetic resin.
• Persistence: No volatilization, no exudation, no migration, no dissolution during plastic processing and application.
• Chemical stability: It will not decompose during plastic processing and application, and will not chemically react with synthetic resin and other components.
• Non-toxic: No toxic effects on the human body. The price is low.

The method of adding additives depends on: the physical form and melting characteristics of the synthetic resin; the physical form and concentration of the additive; the dispersion and solubility of the additive in the compound; and the final physical state of the compound. When adding, high-speed mixing, banburying and extrusion are often used. The effect of additives depends on the correct order of addition in addition to their mechanism of action. The general recommendation is to add 0.3%

Plastic additives can be divided into seven categories according to their specific functions: additives that improve processing performance, such as heat stabilizers, lubricants, etc. Additives to improve machining performance, such as plasticizers, tougheners, etc. Additives to improve surface properties, such as antistatic agents, coupling agents, etc. Additives to improve optical performance, such as coloring agents. Additives to improve aging performance, such as antioxidants, light stabilizers, etc. Additives that reduce the cost of plastics, such as extenders, fillers, etc. Add other additives with specific effects, such as foaming agent, flame retardant, anti-mold agent, etc.