Characterization of tribocharging properties of powder paint

Abstract

The chargeto-mass ratio (q/m) of individual particles plays a vital role in the powder coating process. Simultaneous measurements of particle size and electrostatic charge were performed on triboelectrically charged powder paint and other powders in the particle size range 1.0 to 65.0 pm in diameter. An electrical single particle aerodynamic relaxation time (E-SPART) analyzer was used to measure electrostatic charge (q) and aerodynamic size (d,) distributions on a [ 101 D. A. Hays, "Contact electrification between metals and polymers: effect of surface oxidation

Generation of bipolar electric fields during industrial handling of powders

“…The generation of bipolar charges has been known to occur in powders used in various industrial applications, which require pneumatic conveying or fluidization (Cartwright et al, 1985;Mazumder et al, 1994;Singh and Hearn, 1985). Interestingly, this bipolar charging appears to be found both in powders having similar or dissimilar chemical compositions with the common characteristic being that they consist of differing sizes (Zhao et al, 2000).…”

Corona Compared with Triboelectric Charging for Electrostatic Powder Coating

“…Charge to mass ratio establishes the effectiveness of electrostatic forces working against the gravitational and aerodynamic forces in delivering the charged powder to the substrate (Taylor and Lawrence 1985). As particle size decreases, the charge to mass ratio increases (Bailey 1998, Mazumder and others 1994) and smaller particles are therefore more influenced by electrostatic forces. Consequently, TE improvement attributable to electrostatics is greatest for small and easily charged particles.…”

“…With electrostatic charging, larger particles attain a higher total charge than smaller particles, but the charge to mass ratio decreases with increasing aerodynamic diameter for both corona (Bailey 1998) and triboelectric (Mazumder and others 1994) charging. Since electrostatic adhesive forces increase with increasing charge to mass ratio, (Stötzel and others 1997), smaller particles experienced improved adhesion to the substrate.…”

“…Accordingly, the particles charged with the corona system should have stronger adhesion than triboelectrically charged powder due to the effect of ionic charge and electrostatic force compression. Among the particles charged triboelectrically, the highest charge to mass values, and so greatest electrostatic forces, should be small particles (Bailey 1998; Mazumder and others 1994), and those particles charged with teflon rather than nylon (Hughes 1989; Banerjee and Law 1998). These highly charged particles should experience higher forces of adhesion.…”