Electrostatic Charging and Deposition of Powder Coatings

Wu, Souheng

doi:10.1080/03602557608063114

Cited by 26 publications

(23 citation statements)

References 15 publications

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“…Electrospray deposition (ESD) with direct current (DC) fields was first developed by Blumberg et al of Los Alamos National Laboratory in 1962 as a means to generate thin sources of radioactive particles . Simultaneously, electrostatic spray became increasingly common in the 1960s, and bell-type sprayers are now a standard method for automotive painting, crop spraying, and pharmaceutical coating. − The advantage of electrostatic sprays in these applications is that the spray is directed to a grounded workpiece or leaf, thus resulting in highly efficient coverage of even the shadowed components. Because of the buildup of charge and ionization of the surrounding air and parts, self-limiting spray (SLS) effects have been observed in electrostatic powder spray. ,− …”

Section: Introductionmentioning

confidence: 99%

Obtaining Thickness-Limited Electrospray Deposition for 3D Coating

Lei

Kovacevich

Nitzsche

et al. 2018

ACS Appl. Mater. Interfaces

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Electrospray processing utilizes the balance of electrostatic forces and surface tension within a charged spray to produce charged microdroplets with a narrow dispersion in size. In electrospray deposition, each droplet carries a small quantity of suspended material to a target substrate. Past electrospray deposition results fall into two major categories: (1) continuous spray of films onto conducting substrates and (2) spray of isolated droplets onto insulating substrates. A crossover regime, or a self-limited spray, has only been limitedly observed in the spray of insulating materials onto conductive substrates. In such sprays, a limiting thickness emerges, where the accumulation of charge repels further spray. In this study, we examined the parametric spray of several glassy polymers to both categorize past electrospray deposition results and uncover the critical parameters for thickness-limited sprays. The key parameters for determining the limiting thickness were (1) field strength and (2) spray temperature, related to (i) the necessary repulsive field and (ii) the ability for the deposited materials to swell in the carrier solvent vapor and redistribute charge. These control mechanisms can be applied to the uniform or controllably-varied microscale coating of complex three-dimensional objects.

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Section: Introductionmentioning

confidence: 99%

Obtaining Thickness-Limited Electrospray Deposition for 3D Coating

Lei

Kovacevich

Nitzsche

et al. 2018

ACS Appl. Mater. Interfaces

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“…Various curing methods exist. [7,11,12] However, the most widely used method is thermal curing. [6] Once the coating is cured, the coating process is complete.…”

Section: Doi: 101002/adem202300465mentioning

confidence: 99%

Electrostatic Powder Coating as a Novel Process for High‐Voltage Insulation Applications

2023

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A novel strategy for manufacturing of the main insulation of high‐voltage rotating machines is presented. The developed process is based on established electrostatic powder coating equipment. Using complete automation enables the precise and reproducible application of homogeneous powder coating layers. Individual layers can be stacked by process repetitions to achieve a desired layer thickness. This coating strategy alters the particle deposition process by introducing additional capillary bridges that significantly increase powder adhesion. A systematic parameter study is performed to provide process–structure relations connecting various process parameters with the resultant coating thickness and homogeneity. The parameters of the developed coating process are iteratively improved to maximize coating homogeneity and minimize defect density, the most critical parameters in high‐voltage insulation applications. The obtained powder coatings with a target thickness of 1.5 mm are subjected to electrical testing to examine the partial discharge activity as a key criterion for a functional insulating coating. The measurements reveal no significant partial discharge activity up to an electric field strength of 10 kV mm−1, demonstrating that this novel strategy for the production of the main insulation of high‐voltage rotating equipment surpasses the state‐of‐the‐art process in terms of partial discharge activity.

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“…In the powder coating process, the employed particles first receive charge in the vicinity of the gun tip by the so-called primary charging [5], but at the same time the corona current is reduced due to the shielding effect and the deceleration of ions incurred by the charged particles [7]. While adhering on the substrate, the deposited particles may accept additional charge by the secondary charging, resulting from the convergence of the field and ions on the substrate [5].…”

Section: Introductionmentioning

confidence: 99%

“…While adhering on the substrate, the deposited particles may accept additional charge by the secondary charging, resulting from the convergence of the field and ions on the substrate [5]. The charging efficiency of the particles is usually evaluated by their charge-to-mass ratio (Q/M) [5]:…”

Section: Introductionmentioning

confidence: 99%

“…Corona charging is typically characterized by a non-uniform, highvoltage and low-amperage electric field between the gun tip and the substrate [2,3]. In this process powder particles become charged while passing through the ionized region at the vicinity of the gun tip, and thereafter deposit on the substrate mainly depending on their electrostatic forces [5]. One challenge for corona charging lies in coating irregularly shaped parts, for the electric field lines cannot reach recessed areas or cavities on these parts [2,3].…”

Section: Introductionmentioning

confidence: 99%

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