Factors for Impacting on Antistatic Effect of Plastics
The function of antistatic agent is to reduce the surface resistance and reduce and eliminate the static charge on the surface of plastics. Thus, the anti-static effect of plastics is subject to impact of multiple factors. For internal mixing type, the compatibility of antistatic agent and plastics directly impacts on the anti-static property of plastics. In case of good compatibility, the antistatic agent molecule is hard to be migrated due to the intermolecular attraction; in case of poor compatibility, the anti-static agent will soon be separated out of the surface, resulting in excessive exudation, which will not only impact on the appearance and processability of products and shorten the antistatic validity period. Therefore, during actual use, the anti-static agent shall be compatible with the plastics properly. After the surface antistatic agent is depleted, the internal anti-static molecule can be timely effused out of surface to recover the anti-static property. Generally, ionic anti-static agent shall be used for the polar resin, and low- polarization non- ionic anti-static agent shall be used for weak-plate or non-polar resin.
The glass transition temperature (T) of plastics directly impacts on the migration speed of anti-static molecule. For plastics lower than room temperature, the link molecule moves very violently, which is beneficial to the surface migration of internal anti-static agent molecule, the anti-static property of plastics, such as PE and PP, etc., is easy to be maintained. For some plastics higher than room temperature, such as PS, PVC and ABS, etc., because the molecular chain has been at the frozen state, the anti-static agent is hard to be migrated to the surface.
The interaction of anti-static agent and other plastic agents will also impact on the exertion of anti-static property, such as simultaneous addition of anti-static agent and lubricant. The recombination of anti-static agent and halogen-free flame retardant, etc. must take into account of their mutual impact. In addition, the crystallinity of plastics, additive amount of anti-static agent and many external factors, particularly, relevant ambient temperature, have different effects on anti-static effect of plastics.
After knowing the factors impacting on anti-static effect, the anti-static effect of plastics can be effectively controlled through selection of raw materials and anti-static agent.