1、Designation: D 2805 96a (Reapproved 2003)Standard Test Method forHiding Power of Paints by Reflectometry1This standard is issued under the fixed designation D 2805; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONUsing equations derived from Kubelka-Munk
3、turbid media theory (1-4)2(see Annex A1), thereflectance of a coating can be predicted for any film thickness from measurements made at only one.On this basis several rapid and accurate test methods (5, 6) have been developed for determininghiding power. In the past such test methods have been consi
4、dered difficult due to complexities,apparent and actual, in the treatment of data. The present test method has been simplified in thisrespect, primarily by adapting it fully for computer calculations.Although the use of broad-band reflectometry makes this test method theoretically valid only fornonc
5、hromatic (white or gray) colors, good agreement has been obtained with chromatic paints as well.This is undoubtedly because the experimental measurements are made fairly close to the hiding powerend point so that the Kubelka-Munk extrapolation and thus any associated error is relatively small.This t
6、est method is therefore recommended without restriction as to color.1. Scope1.1 This test method covers the determination, withoutreference to a material paint standard, of the hiding power ofair dry coatings with Y tristimulus values greater than 15 %.With appropriate modification, it can also be u
7、sed to testbaking finishes.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations p
8、rior to use.2. Referenced Documents2.1 ASTM Standards:D 344 Test Method for Relative Hiding Power of Paints bythe Visual Evaluation of Brushouts3D 1475 Test Method for Density of Liquid Coatings, Inks,and Related Products3D 3924 Specification for Standard Environment for Condi-tioning and Testing Pa
9、int, Varnish, Lacquer, and RelatedMaterials3E 284 Terminology of Appearance3E 1247 Practice for Identifying Fluorescence in Object-Color Specimens by Spectrophotometry3E 1331 Test Method for Reflectance Factor and Color bySpectrophotometry Using Hemispherical Geometry3E 1347 Test Method for Color an
10、d Color Difference Mea-surement by Tristimulus (Filter) Colorimetry3E 1349 Test Method for Reflectance Factor and Color bySpectrophotometry Using Bi-Directional Geometry33. Terminology3.1 DefinitionsFor definitions used in this test method,see Terminology E 284.3.2 Definitions of Terms Specific to T
11、his Standard:3.2.1 contrast ratiothe ratio of the reflectance of a film ona black substrate to that of an identical film on a whitesubstrate.3.2.1.1 CWthe contrast ratio with a white substrate ofreflectance W.Thus: CW5 R0/RW3.2.1.2 Cthe contrast ratio with a white substrate forwhich W = 0.80.Thus: C
12、 5 R0/R0.801This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.26 on Optical Properties.Current edition approved May 10, 2003. Published June 2003. Originallyapproved in 1969.
13、Last previous edition approved in 1996 as D 2805 96a.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3Annual Book of ASTM Standards, Vol 06.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
14、tates.3.2.2 reflectancethe daylight luminous diffuse reflectancefactor (specular reflection excluded). Also referred to in thistest method as the Y-tristimulus value. This value may beexpressed as a percent or a decimal fraction, the latter beingpreferred and usually required for mathematical calcul
15、ations.3.2.2.1 reflectivity, Rthe reflectance of film thick enoughto have the same reflectance over both a black and a whitesubstrate.3.2.2.2 R0the reflectance of a film on a black surface witha reflectance of 1 % or less, which is effectively zero for thepurpose of this test.3.2.2.3 Wthe reflectanc
16、e of a white substrate.3.2.2.4 RWthe reflectance of a film applied on a whitesubstrate of reflectance W.3.2.2.5 R0.80the reflectance of a film applied on a sub-strate having a reflectance of 80 %, which is the standardwhite-substrate reflectance in paint technology.3.2.3 scattering coeffcient, Sthe
17、ability of a material tointernally scatter and thereby reflect light; expressed in this testmethod in the same units as spreading rate.3.2.4 spreading rate, Hfilm area per unit volume ofcoating, in this test method expressed in square metres per litre(m2/L). It is also frequently expressed in square
18、 feet per gallon(ft2/gal).3.2.4.1 spreading rate, HXan experimentally determinedvalue of H.3.2.4.2 spreading rate, HCvalue of H at a specifiedcontrast ratio C.3.2.4.3 hiding power, H0.98the spreading rate at the con-trast ratio C = 0.98.NOTE 1It should be emphasized that a contrast ratio of 0.98 doe
19、s notrepresent visually complete hiding, nor does it indicate that the samecontrast ratio holds at every wavelength.4. Summary of Test Method4.1 The reflectivity Rof the coating is determined fromreflectance measurements on black and white hiding powercharts.4.2 The scattering coefficient S of the c
20、oating is determinedfrom R, and the reflectance R0and spreading rate HXof a filmapplied on black glass.4.3 The hiding power, H0.98of the coating is calculatedfrom the reflectivity Rand the scattering coefficient S.4.4 As an optional procedure the contrast ratio C at aspecified spreading rate HCis ca
21、lculated from Rand S.5. Significance and Use5.1 This is a precise instrumental method giving resultshaving an absolute physical significance without reference to acomparison paint. It should be used when maximum precisionand minimum subjectivity are required, as in testing specifica-tion coatings or
22、 evaluating the hiding efficiency of pigments.5.2 Hiding power Test Method D 344 is visual instead ofinstrumental, and gives results that are relative to a materialstandard instead of absolute. It is less precise than Test MethodD 2805 but more closely aligned with practical paintingprocedures.6. Ap
23、paratus and Materials6.1 Substrates:6.1.1 Black Glass Panels,4minimum size 200 by 200 mm,and approximately 6-mm thick.6.1.2 Black and White Paper Charts5The surface shall besmooth and level, and impervious to paint liquids. The blackarea shall have a maximum reflectance of 1 % and the whitearea a mi
24、nimum reflectance of 78 %. The white area shall benon-fluorescent, as observed visually under ultra-violet illumi-nation, or determined in accordance with Practice E 1247.6.2 Balance, accurate to 0.1 mg.6.3 Glass SlidesRound or square plates of thicknesssimilar to that used for microscope specimen s
25、lides, with aminimum area of 40 cm2.6.4 Reflectance-Measuring Instrument6One that allowsonly diffusely reflected, radiant flux to be incident upon themeasuring element. It shall employ a photometric system,including source, filters, and receptor, that provides a responseclosely similar to the produc
26、t of the spectral luminous effi-ciency function of the CIE standard observer and source C.Itshall provide readings to at least the third decimal place andpermit estimation to the fourth.6.5 Template,7with a film area approximately 100 cm2determined to the nearest tenth. Record the exact value on Lin
27、eC of the worksheet shown in Fig. 1.6.6 Doctor Blade Film Applicators, width 150 mm, clear-ances 50, 75, 100, 125, 150, 175, and 200 m.NOTE 2With doctor blades made in the United States, estimate 25mm/in. and 25 m/mil. Bird-type applicators are usually marked with theirhalf clearance.6.7 Computer an
28、d Software, for solving the relevantKubelka-Munk equations.7. Procedure7.1 General Instructions:7.1.1 Film ApplicationMake drawdowns manually with asmooth uniform motion, at the rate of about 6 cm/s. Hold papercharts flat by a vacuum plate or other suitable device whilemaking drawdowns.7.1.2 Reflect
29、ance MeasurementsMeasure the reflectanceof each test area at a minimum of three locations, reading orestimating to four decimal places and calculating mean values4The sole source of manufacturer of the black Carrara glass known to thecommittee at this time is The Leneta Co., 15 Whitney Rd., Mahwah,
30、NJ 07430. Ifyou are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.5The sole source of manufacturer of the charts known to the
31、 committee at thistime is the Leneta Co., 15 Whitney Rd., Mahwah, NJ 07430. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may
32、attend.6Conforming with Test Methods E 1331, E 1347, or E 1349. Other methods formeasuring the CIE-Y tristimulus value (specular reflection excluded) are permis-sible.7The sole source of supply of the template known to the committee at this timeis Paul Gardner Co., 316 N. E. First St., Pompano Beach
33、, FL33061. If you are awareof alternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.D 2805 96a (2003)2to the same. Place charts over a white s
34、urface and black glassover a black surface while measurements are being made.7.1.3 Record KeepingRecord all data on a copy of theworksheet form specified in Fig. 1. Typical data entries areshown in Fig. 2.7.1.4 Weight MeasurementsMake all weighings to 0.1 mgon the analytical balance.7.2 Paint densit
35、y, DDetermine the density in g/mL to fourdecimal places in accordance with Test Method D 1475 andrecord on Line A of the worksheet (Fig. 1). If the density is firstdetermined in pounds per gallon, divide by 8.3454 to obtain itin grams per millilitre.7.3 Nonvolatile Content, NSandwich 0.3 mL of paint
36、(dispensed with a 1-mL syringe) between two previouslyweighed slides, squeezing them together so that the paintspreads to a diameter of about 45 mm. Reweigh to obtain theweight of paint sample. Separate the slides, allow the films todry, and weigh a third time to determine the dry weight. Thencalcul
37、ate the nonvolatile content of the paint as a decimalfraction to four places. Run in duplicate and report the meanvalue to three decimal places on Line B of the worksheet (Fig.1).7.4 Applicator SelectionMake trial drawdowns on blackand white charts at clearances of 100, 150, and 200 m. Allowthem to
38、dry overnight and measure their contrast ratios. Basedon the results select the best applicator for a contrast ratio of0.97 6 0.01, which may be one of the trial applicators or oneof intermediate clearance. If it seems necessary, make anadditional trial drawdown to confirm the correct applicator.7.5
39、 Drawdowns on Glass and Charts Using the applicatorselected from 7.4, make four drawdowns each on black glassand on black and white charts in accordance with 7.1.1. Leaveenough of the white area of each chart uncoated to permitmeasurement of the reflectance W.FIG. 1 Work Sheet FormD 2805 96a (2003)3
40、7.6 Drying of the FilmsImmediately after applicationplace each drawdown horizontally in a well-ventilated dust-free location, with all drawdowns in close proximity to oneanother to assure identical drying conditions, and allow to drya minimum of 40 h before testing. Drying conditions for filmapplica
41、tions and nonvolatile determinations shall be the same,and in accordance with Specification D 3924.7.7 Reflectance MeasurementsOn the second or third dayafter application measure the reflectances on all of the draw-downs within as brief a time span as possible, alternating themeasurements between ch
42、arts and glass rather than doing firstall one and then the other. Enter the values of R0, RW, and W forcharts into Section D of the worksheet, and the values of R0forglass into Section E.7.8 Weight of Dry Film, MAfter all of the reflectances aremeasured, position the template on the glass panels, ea
43、ch in itsturn, and scrape off the surplus paint with a razor blade, toleave film areas defined by the template. If the template area isnot already specified, measure one of the resultant filmscarefully to determine its area in square centimeters to thenearest tenth. Record this value on Line C of th
44、e worksheet(Fig. 1) as the characteristic area of the template. Then scrapeoff each paint film carefully into a weighing dish, weigh to 0.1mg, and record the weights M in Section E of the worksheet,entering each weight adjacent to the value of R0for the sameglass panel.8. Calculation8.1 In general,
45、make the calculations and record to foursignificant figures and final report values to three. Entercalculated results in the worksheet (Fig. 1). Typical entries areshown in Fig. 2.8.2 Contrast Ratio CWand Reflectivity RFrom the dataentered in Section D of the worksheet calculate CWand Rforeach of th
46、e four charts, thus:CW5 R0/RW(1)FIG. 2 Typical Work SheetD 2805 96a (2003)4R5 fR0, RW, W!Enter the values, as they are calculated, in the appropriatecolumns of Section D, then calculate and likewise enter theirmeans.8.3 Spreading Rate HXFrom the data recorded in theworksheet on Lines A, B, and C and
47、 in Section E, calculate thespreading rate Hxfor each of the four glass panels, thus:HX5A 3 N 3 D10Mwhere:HX= spreading rate, m2/L,A = template area, cm2,N = nonvolatile content of the paint,D = density of the paint, g/mL, andM = dry film weight, g.and enter the values in the appropriate column of S
48、ection E.8.4 Scattering Coeffcient S and Hiding Power H0.98Continuing on Section E of the worksheet (see Fig. 1), andusing the mean value of Rfrom Section D, calculate for eachof the glass panels, first S and then H0.98in square millimetresper litre as follows:S 5 fR0, R, HX! (2)H0.985 fS, C, R! giv
49、en C 5 0.98 (3)Enter the values as they are calculated in the appropriatecolumns of Section E, then calculate and likewise enter theirmeans.8.5 Contrast Ratio C at a Specified Spreading Rate HIfdesired, calculate the contrast ratio at a specified spreading rateusing the mean values of Rand S from worktable Sections Dand E, of the worksheet (Fig. 1), thus:C 5 fS, H, R! (4)9. Report9.1 Enter the following information on the indicated line inFig. 1, Section G:9.1.1 Hiding Power, H0.98Enter the mean value of H0.98from Section E,
