Antistatic Technology of Polypropylene Materials

PP is a semi-crystalline polymer with excellent mechanical properties, heat resistance, chemical resistance and formability. It has been widely used in automotive, home appliances and construction industries.

Because of its small molecular polarity and poor water absorption, PP has strong electrical insulation (surface resistivity as high as 1016～1018Ω). During production and application, the surface of PP will produce and accumulate static electricity due to friction, stripping or induction. This results in electrostatic hazards, such as vacuum, discharge, breakdown, or even combustion or explosion.

Therefore, antistatic automotive PP materials have become one of the important directions in the field of plastic modification.

The antistatic properties of PP materials have been studied. By adding small molecule antistatic agents, polymer antistatic agents and conductive fillers, the conductive properties of PP can be improved to the level of dust-proof and antistatic.

At present, the addition of small-molecule antistatic agent is the main method. The small molecular antistatic agent contains hydrophilic group and lipophilic group. The action mechanism of antistatic agent can be divided into four stages:

Stage 1, during extrusion, antistatic agents are uniformly distributed in PP materials.

Stage 2, after extrusion, the antistatic agent begins to migrate to the surface.

Stage 3, the antistatic agent forms a layer of hydrophilic group outward and oil group inner layer on the surface.

Stage 4, the surface hydrophilic group adsorbs water in air to form conductive layer and eliminate static electricity. That is to say, small antistatic agents are not completely compatible with resins. When they migrate from the resin to the surface of the resin, their hydrophilic groups combine with water in the air to form a thin layer of water, which acts as a hydrophobic charge. Thus reducing the surface resistivity of plastics.

The study shows that the higher the content of small molecular antistatic agent, the lower the surface resistivity of the material.

The low molecular antistatic agent mixed with PP by high speed stirring is more uniform and the surface resistivity of the material is lower.

When the cooling rate is fast, the surface resistivity of the material is lower.

With the increase of environmental humidity and the prolongation of time, the antistatic performance of PP is obviously improved.

In addition, the effect of the content of antistatic agent on the properties of PP materials shows that the tensile strength and surface hardness of PP materials decrease with the increase of the content of antistatic agents.

The current research focuses on the influence of antistatic agents on the antistatic and mechanical properties of the materials, while the influence of the composition of PP materials on the antistatic effects of antistatic agents is less.

Heat-resistant, durable, high-efficiency, multi-functional, wide applicability and variety series of antistatic agents are receiving more and more attention.