The main cause of static electricity is friction. When two solid materials come into contact and leave quickly, one of them has a greater ability to absorb electrons and transfer them to the surface of the material. The surface of the electron gains a negative charge, while the other has a positive charge due to the loss of the electron.

The main factors causing static electricity:

1. Material properties include internal chemical composition, internal structure, stress-strain mechanical characteristics, material shape and electrical conductivity, etc.

The electrical conductivity of a material has a dual effect on static electricity. First, if a material is a conductor, the charge moves freely on its surface, where it is distributed evenly rather than remaining in the local place where it was generated. This surface distribution of charge causes only a low voltage. Any part of the conductive material that comes into contact with the ground immediately transmits an electric charge to the ground. And insulation material and conductor are different, like most of the substrate in the paper, plastic film, etc., the generation of static electricity will form a higher voltage, can not be eliminated by grounding.

2. Ambient conditions include the composition of the gas around the object (material) in contact with pressure, temperature, humidity, etc.

3. The mechanical action includes the type of contact, contact time, contact area, separation velocity and the nature of the material force, etc. In general, the closer the two materials come into contact or the faster the separation, the greater the electrostatic charge.

4. Different polarity of static electricity will be generated when the materials cooperate with the friction between different materials. Different materials have different electrostatic strengths.