1、Designation: D5861 07 (Reapproved 2013)Standard Guide forSignificance of Particle Size Measurements of CoatingPowders1This standard is issued under the fixed designation D5861; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the significance of referencing thetechniques used whenever specifying the particle size distr
3、ibu-tion of a coating powder.2. Referenced Documents2.1 ASTM Standards:2D1921 Test Methods for Particle Size (Sieve Analysis) ofPlastic MaterialsD3451 Guide for Testing Coating Powders and PowderCoatings3. Terminology3.1 Definitions:3.1.1 coating powders, nthese are finely divided particlesof organi
4、c polymer that generally contain pigments, fillers, andadditives and that remain finely divided during storage undersuitable conditions.3.1.2 powder coatings, nthese are coatings that areprotective, decorative, or both; and that are formed by theapplication of a coating powder to a substrate and fus
5、ed intocontinuous films by the application of heat or radiant energy.4. Significance and Use4.1 This guide describes the need to specify the measuringtechnique used whenever quoting the particle size distributionof a coating powder.4.2 This guide is for use by manufacturers of coatingpowders and by
6、specifiers for process control and productacceptance.5. Particle Size of Coating Powders5.1 The size of the particles comprising a coating powderplays a critical role in the fluidization, application, and recla-mation of the powder, and in the final appearance of the coatedpart. Coating powders are
7、comprised of particles of widelydiffering sizes, from as low as about 1 m to as high as about150 m. Collectively, the individual particles form a sizedistribution, defined by the percentages of particles present ofa given size or within a given size range. There are generallyfew particles at the low
8、 and high ends of the distribution, themajority being in the 25 to 65-m range. The distribution canbe described by an actual plot of the particle size distribution,or by numerical attributes of the distribution, such as thecalculated values of its mean, median, mode, and span. Themean represents the
9、 average particle size (the sum of all theparticle sizes divided by the number of particles). The medianrepresents a size such that half the particles are larger than itand half the particles are smaller than it. The mode representsthe most frequently occurring particle size. For all coatingpowders
10、these three figures are numerically different. The spanis an indication of the width of the particle size distribution.Referring to Table A1.1, the span is calculated by subtractingthe d10 from the d90 and then dividing by the d50 or medianparticle size.5.2 The particle size distribution is generall
11、y chosen by thecoating powder manufacturer from knowledge of the applica-tion technique, the required cured film thickness, surfaceappearance, and performance. Once the desired particle sizedistribution has been selected, it needs to be monitored toensure consistency from batch to batch and, indeed,
12、 withineach batch. Occasionally the coating powder applicator mayspecify the particle size from knowledge of the specificapplication equipment or customer requirements, or both.5.3 It is important for all involved to understand that thenumerical data comprising a particle size distribution aresignif
13、icantly dependent on the technique used to obtain them. Itis, therefore, of little use to quote or specify a particle sizedistribution, and even less a single particle size, without alsodefining the technique used to obtain that measurement, or, ifa single size, whether it is, for example, the mean,
14、 median ormodal value.1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.51 on Powder Coatings.Current edition approved June 1, 2013. Published July 2013. Originally approvedin 1995
15、. Last previous edition approved in 2007 as D5861 07. DOI: 10.1520/D5861-07R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page o
16、nthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Measurement of Particle Size6.1 There are a wide variety of instruments currently avail-able for measuring the particle size distributions of coatingpowders. Actual
17、sieving, such as described in Test MethodsD1921, where the percentage weight of coating powder re-tained on sieves of known mesh size is measured, is relativelyinexpensive and direct. It is, however, significantly slower thanindirect measurement techniques, such as laser scattering andelectrolytic c
18、onductivity, such as described in Guide D3451.With indirect measurement techniques, a secondary effect,induced by the presence of the coating powder particles, ismeasured, such as changes in light scattering or in theconductivity of an electrolyte. These effects are analyzed usinga specific theoreti
19、cal algorithm, unique to the measurementtechnique, and the particle size distribution calculated thatwould cause the measured changes. Various other statisticaldata on the distributions, such as the mean, the median, themode, and the span are also often automatically calculated.6.2 Secondary measure
20、ment techniques make assumptionssuch as the measured particles being spherical, and do notacknowledge the fractured, randomized shapes the particlesactually possess. Others require the preparation of a suspensionof the particles in a liquid, which could alter the physical stateof particle agglomerat
21、es present in the dry state. Even therequired processing for dry powder measurement techniquescould mechanically break up larger particles or agglomeratesinto smaller ones, or both.6.3 Thus not only can the theoretical algorithms for themeasuring techniques be quite different, but each measurementte
22、chnique can cause the particle size distribution to changeduring sample preparation or the measurement process itself,or both. This simply serves to emphasize that once a measure-ment technique has been selected, there is still need forconsistency in all aspects of its operation.7. Effect of Using D
23、ifferent Measurement Techniques7.1 To illustrate the numerical differences in measuredparticle size that can be found when different measurementtechniques are used, the same coating powder was provided toa number of participants, who measured the particle size of thesample, usually in triplicate, us
24、ing their own preferred tech-nique. Participants included coating powder manufacturers,raw material suppliers to the powder coating market, andmanufacturers of particle size measuring equipment.7.2 The data obtained can be found in Annex A1 and AnnexA2. They have been transposed into two respective
25、standardformats for ease of comparison. Where possible, additionalnumerical data were extracted from the original plots ofparticle size distribution. In these instances, such figures areenclosed in parentheses in Annex A1 (see Figs. A1.1-A1.14).Some of the original plots of particle size distributio
26、n werereplotted for clarity, with a consistent ordinate and abscissa, of“percentage of particles in a given range” and “log (particlesize in m)” respectively. These standardized distributionsconstitute Figs. A1.1-A1.14.7.3 It can be seen that there are distinct differences betweenthe data acquired b
27、y different techniques, and by the sametechnique when the machine manufacturer or model ischanged. There are even differences when instruments with thesame model number are used in different laboratories.7.4 It must be emphasized that these data are not presentedin order to recommend one measurement
28、 technique overanother, or one participating piece of equipment over anothernonparticipating piece of equipment, but rather to clearlyillustrate the necessity of defining how a size measurement isobtained when quoting any numerical value regarding particlesize.8. Measurement Techniques Used8.1 Agita
29、ted Sieving, Dry Sampling8.2 Electrolyte Conductivity, Wet Sampling8.3 Laser Scattering, Dry Sampling8.4 Laser Scattering, Wet Sampling8.5 Sedimentation/X-Ray Absorption, Wet Sampling8.6 Mercury Porosimetry, Dry SamplingNOTE 1Mercury porosimetry requires the use of mercury. The propersafety precauti
30、ons should be taken when handling mercury as a hazardouselement.8.7 Note that some of the instruments were used indepen-dently of each other, and by more than one participant.9. Keywords9.1 coating powder; electroconductivity; laser scattering;mercury porosimetry; particle size analysis; powder coat
31、ing;sedimentation; sieve analysis; X-rayD5861 07 (2013)2ANNEXES(Mandatory Information)A1. DATA AS ILLUSTRATED IN Table A1.1TABLE A1.1 Particle Size Data from Secondary Measurement TechniquesAInstrumentNumberMethodPercent of Particles Less Than Micron Size in Body of Table Mean,(m)Median,(m)Mode,(m)5
32、1020253040506070758090951 Laserscattering(dry)11.811.311.623.022.422.732.231.932.042.542.342.360.459.659.332.231.932.02 Laserscattering(wet)10.611.010.829.730.930.261.164.662.233.535.134.229.730.930.23 Laserscattering(dry)8.48.58.428.728.628.658.858.858.934.835.235.028.728.628.636.936.837.04 Lasersc
33、attering(dry)8.38.48.426.126.226.151.952.452.226.126.226.15 Laserscattering(dry)12.612.812.733.333.233.063.263.363.836.136.136.133.333.233.06 Laserscattering(wet)46.146.146.0(37.0)(37.0)(37.0)7 Laserscattering(dry)9.67.69.830.329.230.560.459.860.032.931.732.930.329.230.58 Laserscattering(dry)12.412.
34、212.432.732.132.562.160.961.235.635.235.632.732.132.59 Laserscattering(dry)6.86.410.49.815.914.821.119.426.024.030.628.435.332.940.438.146.644.455.754.564.564.530.628.4(36.2)(31.0)10 Electrolyteconductivity(wet)14.511.011.235.723.626.274.043.358.634.022.725.735.723.626.238.926.327.411 Electrolytecon
35、ductivity(wet)7.66.46.018.113.712.338.429.424.617.713.812.418.113.712.319.414.312.812 Laserscattering(dry)9.69.89.917.818.418.530.331.331.444.745.845.858.060.359.732.233.633.330.331.331.438.938.938.913 Sedimentation(X-rayabsorption)(11)(10)(10)(25)25.125.0(42)(46)(46)(25)25.125.027.227.114 Mercurypo
36、rosimetryB(9.0)(9.0)(9.0)24.822.424.2(130)(90)(100)24.822.424.224.420.324.515 Laserscattering(dry)(4.0)(3.8)(3.8)(6.2)(6.2)(6.2)(10.4)(10.3)(10.2)(12.5)(12.3)(12.2)(14.6)(14.4)(14.2)(19.0)(18.6)(18.5)(23.5)(23.4)(23.2)(28.9)(28.5)(28.4)(34.3)(34.1)(34.0)(37.8)(37.4)(37.4)(41.7)(41.2)(41.0)(53.0)(52.
37、1)(52.0)(63.0)(62.4)(62.2)(23.5)(23.4)(23.2)35.835.735.6AAll figures in the body of the table are in microns and are volume based except for instrument No. 13 data which are weight based. Figures in ( ) were not providedexplicitly, and so have been estimated from the original data/graphs.BData proce
38、ssed after Mayer or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE A2.1 Particle Size Data from Primary Measurement TechniquesInstrumentNumberMethodWeight Percent of Particles Retained at Given Sieve Openings (m)20m20m30m38m45m63m75m90m16 Sieve analysis (dry) 30.129.431.021.621.723.029.729.927.6.16.515.615.11.73.02.9.0.40.40.417 Sieve analysis (dry) .26.728.327.214.714.714.4.TraceTraceTrace.D5861 07 (2013)18
