1、Designation: D 5861 07Standard Guide forSignificance of Particle Size Measurements of CoatingPowders1This standard is issued under the fixed designation D 5861; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 distribu-tion of a c
3、oating powder.2. Referenced Documents2.1 ASTM Standards:2D 1921 Test Methods for Particle Size (Sieve Analysis) ofPlastic MaterialsD 3451 Guide for Testing Coating Powders and PowderCoatings3. Terminology3.1 Definitions:3.1.1 coating powders, nthese are finely divided particlesof organic polymer tha
4、t generally contain pigments, fillers, andadditives and that remain finely divided during storage undersuitable conditions.3.1.2 powder coatings, nthese are coatings that are pro-tective, decorative, or both; and that are formed by theapplication of a coating powder to a substrate and fused intocont
5、inuous 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 specifiers
6、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 comprised o
7、f 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 and high e
8、nds 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 average pa
9、rticle 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 these three
10、 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 generally chosen by
11、 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, withineach
12、 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 aresignificantly dep
13、endent 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, median orm
14、odal value.6. Measurement of Particle Size6.1 There are a wide variety of instruments currently avail-able for measuring the particle size distributions of coatingpowders. Actual sieving, such as described in Test Methods1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated
15、 Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.51 on Powder Coatings.Current edition approved June 1, 2007. Published June 2007. Originallyapproved in 1995. Last previous edition approved in 2002 as D 5861 - 2002.2For referenced ASTM standards, visit the A
16、STM 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 onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
17、ted States.D 1921, where the percentage weight of coating powderretained on sieves of known mesh size is measured, isrelatively inexpensive and direct. It is, however, significantlyslower than indirect measurement techniques, such as laserscattering and electrolytic conductivity, such as described i
18、nGuide D 3451. With indirect measurement techniques, a sec-ondary effect, induced by the presence of the coating powderparticles, is measured, such as changes in light scattering or inthe conductivity of an electrolyte. These effects are analyzedusing a specific theoretical algorithm, unique to the
19、measure-ment technique, and the particle size distribution calculatedthat would cause the measured changes. Various other statisti-cal data on the distributions, such as the mean, the median, themode, and the span are also often automatically calculated.6.2 Secondary measurement techniques make assu
20、mptionssuch 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 agglomerates present in the dry sta
21、te. 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 measurementtechnique can cause the par
22、ticle 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 Different Measurement Tech
23、niques7.1 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, using their own preferred t
24、ech-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 standardformats for ease
25、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 distribution werereplotted for clari
26、ty, 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 by different techniques, a
27、nd 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 technique overanother, o
28、r 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 Agitated Sieving, Dry Sampling
29、8.2 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 precautions should be taken when
30、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 coating;sedimentation; sieve
31、analysis; X-rayD5861072ANNEXES(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)51020253040506070758090951 Lasersc
32、attering(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 Laserscattering(dry)8.38.48.426.126.226.
33、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)12.412.212.432.732.132.562.160.961.235.6
34、35.235.632.732.132.59 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 Electrolyteconductivity(wet)7.66.46.018.113.712
35、.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 MercuryporosimetryB(9.0)(9.0)(9.0)24.822.4
36、24.2(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)(52.1)(52.0)(63.0)(62.4)(62.2)(23.5)(
37、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 processed after Mayer or through the A
38、STM website(www.astm.org).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.D58610718
