Detailed explanation of antistatic technology of polypropylene PP material
PP is a semi-crystalline polymer with excellent mechanical properties, heat resistance, chemical resistance and easy formability. It has been widely used in industries such as automobiles, home appliances, and construction. Because of its low molecular polarity and poor water absorption, PP has strong electrical insulation (surface resistivity is as high as 1016～1018Ω). In the process of production and use, friction, peeling or induction process will generate and accumulate static electricity on the surface of the product. Generate electrostatic hazards, such as dust collection, discharge, breakdown, and even combustion or explosion.
In the winter in the north, due to the dry weather and a lot of dust, a large amount of dust will be adsorbed on the surface of the automobile parts during their placement after injection molding. These dust and dry cloth can hardly be wiped off, and can only be wiped with a damp cloth, which consumes a lot of manpower and material resources; the wiped parts will quickly re-absorb the dust, and the adsorption speed is very fast; static electricity causes the materials in the packaging bag to fail to be completely poured Out, it will be adsorbed on the inner wall of the packaging bag. Therefore, antistatic PP materials for vehicles have become one of the important directions in the field of plastic modification.
People have conducted some researches on the antistatic properties of PP materials. By adding small molecule antistatic agents, polymer antistatic agents and conductive fillers, the conductivity of PP can be improved to achieve a dustproof and antistatic level.
At present, small-molecule antistatic agents are mainly added. Small-molecule antistatic agents contain hydrophilic groups and lipophilic groups, and the mechanism of action The antistatic agent has four stages:
Stage 1. During the extrusion process, the antistatic agent is evenly distributed in the PP material.
In stage 2, after extrusion, the antistatic agent starts to migrate to the surface.
In stage 3, the antistatic agent forms a molecular layer on the surface with hydrophilic groups outward and lipophilic groups inward.
In stage 4, the hydrophilic groups on the surface absorb water in the air to form a conductive layer and eliminate static electricity.
That is to say, the small molecule antistatic agent is not completely compatible with the resin. It migrates from the inside of the resin to the surface of the resin, and its hydrophilic group combines with the water in the air to form a thin layer of water, which plays the role of diverting static charges, thereby Reduce the surface resistivity of plastics.
Studies have shown that the higher the content of small molecule antistatic agent, the lower the surface resistivity of the material. The mixing of small molecule antistatic agent and PP through high-speed stirring is more uniform than the cold roll mixing, the surface resistivity of the material is lower, and the molding is cooled. When the speed is fast, the surface resistivity of the material is lower.
With the increase of environmental humidity and the extension of time, the antistatic performance of PP is obviously improved. In addition, the influence of the content of antistatic agent on the properties of PP material indicates that as the content of antistatic agent increases, the tensile strength and surface hardness of the PP material decrease.
Current research mainly focuses on the influence of antistatic agents on the antistatic and mechanical properties of materials, while the influence of PP material components on the antistatic effect of antistatic agents is less involved.
The research of PP antistatic materials will mainly focus on polymer permanent antistatic agents and composite antistatic agents, which will still be the focus of future research on PP antistatic modification. Antistatic agents with heat resistance, durability, high efficiency, multi-functionality, wide applicability and a series of varieties have attracted more and more attention.
