1. Good chemical stability: Most plastics have good acid, alkali, salt, water and gas resistance. Under normal conditions, they do not react with these substances.

2. High specific strength and stiffness: the strength of plastics is not as high as that of metals, but the density of plastics is small, so the specific strength (_b/p) and specific stiffness (E/p) are quite high. Especially reinforced plastics filled with various kinds of high strength fibers, flakes and powders of metal or non-metal have higher specific strength and stiffness than metals.

3. Low density: low density of plastics is of great significance to reduce the weight of mechanical equipment and save energy, especially for vehicles, ships, aircraft and spacecraft.

4. Good electrical insulation, thermal insulation and sound insulation.

5. Good shaping and colouring properties.

6. Strong bonding ability.

7. Good wear resistance and self-lubrication: Plastics have small friction coefficient, good wear resistance, good self-lubrication, high specific strength and low transmission noise. It can work effectively in liquid medium, semi-dry or even dry friction conditions. It can be made into machine parts such as bearings, gears, cams and pulleys. It is very suitable for low speed and low load occasions.