Plastic is a kind of polymer, and its main component is synthetic resin. In addition, there are some special-purpose additives added as needed, such as plasticizers that can improve plasticity and antioxidants that prevent plastics from aging.

Although the relative molecular weight of polymer is very large, its composition is not complicated and its structure has certain rules. They are polymerized from small molecules. For example, polyethylene plastics are polymerized from ethylene molecules.

There are many kinds of plastics, and their uses are different. For example, polyethylene has good electrical insulation, chemical corrosion resistance, cold resistance and non-toxicity, and can be made into films, which can be used as packaging materials for foods and medicines, as well as daily necessities, insulating materials, pipelines, etc. While PVC has good electrical insulation, chemical corrosion resistance, organic solvent resistance and wear resistance, but it has poor thermal stability, poor air permeability and hardens when it is cold.