Static charge is generated by frictional contact between two non-magnetic materials with different vulnerabilities to electron loss. The process causes electrons to be pulled from the surface of one material and relocated on the surface of the other material. The material that loses electrons ends up with an excess of positive charges and the one that gains electrons ends with an excess of negative charges on the surface.
Various factors such as humidity, degree of contact, friction properties, electrical properties such as resistivity and charge decay properties influence the amount of static charge produced. The build-up of static electricity depends on whether the rate of charge dissipation is greater than the rate of charge generation
Plastics as such have high resistivity and a low dielectric constant, which makes them ideal candidates for the generation of high static charges. High static charges can lead to a number of hazards such as:
Handling problems during transport etc.
Electrostatic spark explosion and resulting fires.
Risk to workers handling the machines i.e. electric shocks.
Antistatic agents are extremely effective in significantly reducing and on most occasions completely eliminating problems caused by high surface resistivities. There are two types of Antistatic agents namely internal and external.Internal antistatic agents are designed to be mixed directly into the material (during extrusion), external antistatic agents are applied to the surface (after extrusion)
Due to the superficial nature of external antistatic agents, Internal antistatic agents are preferred more especially for high quality applications. For example, when the antistatic agent on the surface of plastics is removed by friction or washing, the antistatic agent remained in the plastic migrate to the surface leading to long lasting antistatic effect. In addition, internal antistatic agents are more desirable on economic grounds as no further operations for applying the antistatic agent are required after processing.
How they work?
Internal antistatic agents are added as an additive to the plastics molding compositions. Following this the molecules of the antistatic agent migrate to the surface of the polymer forming a consistent layer on the surface of the plastic. The molecules have hydrophilic and lipophillic areas. The hydrophilic side interacts with the air moisture and binds water molecules while the lipophillic side interacts with the surface of the material. The static charge accumulation in plastics is dissipated, through the conductivity of water absorbed by antistatic agents. At the same time, antistatic agents show the action of reducing the accumulation of frictional static charge. Thus, antistatic effect is obtained.
Cristol 163 Ethoxylated Amine (Synthetic Based)
Cristol 163 is an excellent internal antistatic agent. It finds application in injection moulding, sheet extrusion and films. Cristol 163 is often used in injection moulding and sheet extrusion in conjunction with glycerol monostearate. This combination gives excellent antistatic effects due to the synergistic alliance between the two products. Cristol 163 is also used as a process aid in the production of polypropylene. It is extremely effective for polyolefin and styrenics. The use of Cristol 163 as an antistatic agent reduces dust contamination, handling problems during transport, storage and packaging.