Additives to modify conductivity

Electrostatic spraying, one of the important coating application tech­niques, relies on an electric charge on atomized droplets of the paint for higher transfer efficiency. The charged droplets are attracted to the surface of the target object, which has been grounded. Too high an electrical resistance of the liquid paint material would result in poor application and low transfer efficiency. The resistance of a liquid paint, therefore, should be adjusted for better electrostatic spray application of coatings. A resistivity between 104 and 107 Q m-1 is suitable for good transfer efficiency. While resistivity is normally adjusted using proper solvent combinations, quite often it is sup­plemented by small quantities of quaternary ammonium salts for an improved effect. Care must be taken to decide the correct level, because too high a conductivity will result in charge leakage at the gun, a reduced electrostatic field and lowered transfer efficiency.

Another area where such additives are needed to improve conducti­vity is for imparting antistatic properties. Antistatic additives may be added to hydrocarbon solvents to improve conductivity and hence avoid any electrostatic buildup and risk of spark and fire hazard during transfer, storage and transportation.

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