Plastics are macrolecules, which are polymerized from monomers by addition polymerization or polycondensation reaction. They have medium deformation resistance, which is between fiber and rubber. They are composed of synthetic resins, fillers, plasticizers, stabilizers, lubricants, pigments and other additives. Most of the plastics are light in weight, stable in chemical properties, and will not rust; have good impact resistance; have good transparency and wear resistance; have good insulation and low thermal conductivity; generally good formability, coloring, and low processing cost.