Coating powders - Determination of flow properties of a powder/air mixture
Coating powders - Determination of flow properties of a powder/air mixture
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1 Scope This part of ISO 8130 specifies a method for determining the flow properties of a mixture of coating powder and air. The method reflects commercial practice in powder spraying (see “Bibliography”, Annex B). The results obtained are influenced by the composition of the coating powder, its density, particle size distribution and particle shape, together with the tendency of the particles to agglomerate and to accept a triboelectric charge.
NOTE 1 It is well known that the transport and spraying characteristics of powders are highly dependent on their flow properties in bulk and in air. The procedure described in this method is considered to be more meaningful than the “flow angle” approach sometimes used to evaluate bulk flow properties. In the latter, the angle of the cone formed when a powder is allowed to flow through a vertical funnel on to a horizontal surface is measured. A given mass of powder with good flow properties forms a shallower cone than an equal mass of a powder with poorer flow. The objections to the flow angle method are that it is difficult to obtain a precise measurement and that the powder is used alone, whereas during application it is mixed with air.
Mentioned in the description and other BS standards
