Investigation of the Performance of Fumed Silica as Flow Additive in Polyester Powder Coatings

Abstract

Fumed silica is one of the most commonly used flow additives in the powder coating industry. To investigate the influence of the properties of fumed silica on powder coatings, three different types of fumed silica, Aerosil R812, R972, and R8200, were selected and introduced to an ultra-high-gloss powder paint by the dry-blending method with preset mixing conditions and times. Their effect on the powder flowability, coating application related properties and film properties were carefully studied. The angle of repose (AOR) and bed expansion height data, which represent the semi-dynamic and dynamic flowability of powders respectively, show a strong flowability enhancement for the powders with additives, and R812 exhibits the best performance compared to 8200 and R972, mainly due to its high hydrophobicity and specific surface area. For the ultra-high-gloss powder paint, all the flow additives cause slight gloss reductions, surface roughness increase and a significant effect on the distinctness of image (DOI). The addition of R972 is beneficial to the transfer efficiency of powders compared with the other two, while the additives impose only a minor influence in the Faraday cage effect. The melting and curing dynamics, i.e., gel time, and inclined plate flow, are not affected by the flow additives.

Selective Laser Sintering-Based 4D Printing of Magnetism-Responsive Grippers

“…To improve the flowability of the composite Nd2Fe14B/TPU powder, 1.2 g of fumed silica powder bought from Evonik (Germany) was added to every 100 g of composite powder. The characteristics of fumed silica for the flowability improvement of powder can be proved by previous studies , and the Evonik Web site . The uniform composite powder with Nd2Fe14B weight ratios of 20, 30, and 40 wt % was prepared by blending the above-mentioned types of powder.…”

Preparation and Dispersion Performance of Hydrophobic Fumed Silica Aqueous Dispersion

“…Fumed silica is a kind of amorphous particle with a small size, approximately between 10 and 40 nm, and an extremely large specific surface area [4]. In addition to providing thermal insulation, thickening, thixotropy, and anti-settling [5][6][7][8], it also has the effect of reinforcement, color development, and improving powder fluidity [9][10][11][12][13].…”

“…Hydrophobic fumed silica (HFS) is an aerosol with alkanes, chloromethyl groups, or other hydrophobic functional groups on the surface [20]. Under the joint action of hydrophobic functional groups and hydrogen bonds, a three-dimensional network structure can be formed in a highly polar system, which could provide better rheological (thixotropy) and mechanical properties for waterborne coatings and adhesives compared to other fumed silica [4,21,22]. However, the hydrophobic functional groups also made HFS extremely difficult to disperse in water [23].…”

Experimental and Calculational Study on Effects of Flow Additive on Flowability of Fine Coating Particles

“…Compared to liquid coating, powder coating technology has gained high popularity, because it is not only environmentally friendly but also cost effective for its high powder recyclability and elimination of organic solvent [1][2][3]. However, traditional powder coating has some disadvantages, such as the film surface appearance being inferior to liquid coating and the film thickness being much higher than that of liquid coating.…”