1、Designation: D 2745 00Standard Test Method forRelative Tinting Strength of White Pigments by ReflectanceMeasurements1This standard is issued under the fixed designation D 2745; 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the procedure for determin-ing the relative tinting strength of white pigments by re
3、flec-tance measurements of black tints.1.2 This test method is applicable only for comparing thetest pigment with a reference standard of the same type andgrade.NOTE 1Test Method D 332 describes a procedure for visual assess-ment of blue-tinted samples.1.3 The values stated in SI units are to be reg
4、arded as thestandard. The values given in parentheses are for informationonly.1.4 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 deter
5、mine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 332 Test Method for Relative Tinting Strength of WhitePigments by Visual Observation2D 2244 Test Method for Calculation of Color DifferencesFrom Instrumentally Measured Color Coordinates23. Sum
6、mary of Test Method3.1 Pigment is dispersed in a vehicle and let down withadditional vehicle that has been tinted. Dispersion and letdownare accomplished with a mechanical muller. Both the test andstandard pigments are treated identically. Opaque drawdownsare made of the paint and the Y tristimulus
7、values (green-filterreflectance) of the wet films are measured. The relative tintingstrength of the test pigment is calculated directly from thereflectance values.4. Significance and Use4.1 Tinting strength is one of the most important propertiesof a white pigment. This test method provides a means
8、oftesting this property for quality control.4.2 This test method is a referee method, and the vehicle forpreparing the dispersion and the black for tinting are suggested,but others may be used provided both the purchaser and theseller agree to the changes.4.3 The results obtained with a muller do no
9、t necessarilyagree with industrial situations where different dispersingconditions exist. However, dispersing with a muller is a fast,relatively inexpensive way of testing tinting strength forroutine quality control.5. Apparatus and Materials5.1 Muller, automatic, equipped with a weight that exerts
10、apermanent 220-N (50-lbf) and an additional weight exerting a50-lbf making a total of 445-N (100-lbf). The two glass platesshall be kept sharp by removing from the machine and grindingthem face-to-face with No. 303 optical emery or equivalent,and water.5.2 SpatulaA flexible spatula having a chromium
11、-platedor plastic blade 75 to 150 mm (3 to 6 in.) long, and anotherwith a 75 mm ( 3-in.) tapered blade.5.3 Balances(1) A balance sensitive to 20 mg and (2)ananalytical balance sensitive to 0.4 mg.5.4 VehicleBecause the choice of vehicle may affectresults, a solvent-free vehicle (excluding refined or
12、 low-bodiedlinseed oil) should be agreed upon by the purchaser and theseller.5.5 Tinting BlackA lamp black predispersed in a vehiclesimilar in nature to the test vehicle. Tinting black should beagreed upon between the purchaser and the seller.5.6 ChartEither gray or white lacquered charts cut to aco
13、nvenient size.1This 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 Nov. 10, 2000. Published January 2001. Originallypublished a
14、s D 2745 68 T. Last previous edition D 2745 93.2Annual Book of ASTM Standards, Vol 06.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.7 Color Measuring Instruments, meeting the requirementsof Test Method D 2244.5.8 Film Applicat
15、or 50 or 75 mm (2 or 3 in.) wide with aclearance of 150 m ( 6 mils) to produce wet films about 75 m(3 mils ) thick. This applicator when used as suggested in thetest method will produce an Rfilm.6. Standard6.1 Astandard white pigment of the same type as the sampleto be tested, as agreed upon by the
16、purchaser and the seller.7. Procedure7.1 Place two concentric circles under the base plate of themuller so that they can be clearly seen through the plate. Thecircles can be drawn on a paper and inserted under the plate, orthey can be drawn directly on the underside of the bottomplate. The inner cir
17、cle should be 63 mm (212 in.) in diameterand the outer circle 114 mm (412 in.) in diameter.7.2 Make a preliminary test by dispersing standard whitepigment in a clear vehicle at the pigment volume concentration(PVC) given in Table 1 and adding tinting black to determinethe amount of black required to
18、 provide a reflectivity of 0.42 60.03. Prepare a “black letdown vehicle” by adding tinting blackto clear vehicle so that 1.000 g of the black letdown vehiclewill contain the same amount of black that provided thisreflectivity. Three examples are given in Table 1.7.3 Weigh the pigment to the nearest
19、g with the analyticalbalance in accordance with Table 1 and transfer to the lowerplate of the muller. Add clear vehicle to the pigment inaccordance with Table 1 (Note 2). Mix with a spatula until apaste is obtained. “Pick up” the paste with the spatula andspread it within the area between the two co
20、ncentric circles onthe plate. Close the muller, mull 25 times, and collect the paste.Thoroughly mix the black letdown vehicle in its container.Add1.000 g of black letdown vehicle as specified in Table 1 to thewhite paste and mix in thoroughly with a spatula. Again spreadthe paste within the two conc
21、entric circles, mull 25 times,pickup the paste, spread within the area, and mull a final 25times more. Prepare a reference standard with each series oftest pigments by this same procedure.NOTE 2An analytical balance is specified for referee-type of testing;for routine work, weighing to 20 mg has bee
22、n found satisfactory as analternative procedure. Among the methods of accurately weighing ve-hicles (either the clear or black letdown vehicles) are these two alterna-tives: ( 1) Place a small beaker of vehicle on the weighing pan of thebalance. Remove and transfer vehicle employing the spatula ulti
23、matelyintended for preparing a paste on the muller. Use the weigh-by-differencemethod. (2) Add the vehicle to a tared metal or plastic plate till the correctweight is reached; transfer to the muller by scraping off the plate with thespatula. If the vehicle tends to run, weigh both pigment and vehicl
24、e on theplate making a crater in the pile of pigment to contain the vehicle.7.4 Standardize the color measuring instrument for mea-surement of the green filter reflectance (that is, Y-value) with,if necessary, a wet-film adapter in place. Adjust the colorinstrument to the approximate expected readin
25、g. Draw downthe sample paint on the chart (lacquered side) with theapplicator blade (5.8). Place the film immediately on thereading port, cover the back of the chart with a flat, black panel(for example, black structural glass) to keep the chart flat andprevent exterior light from entering the color
26、 measuringinstrument, and read the reflectance immediately (Note 3),recording the value. Clean the port of the colorimeter thor-oughly with a rag. Draw down the standard paint and readimmediately as before (Note 4). When the reflectance readingof the sample is greater than the standard, the sample i
27、sstronger in tinting strength. When it is lower it is weaker.NOTE 3Flooding will cause drifting in the reflectance reading of somefilms. When the color measuring instrument is already adjusted to theexpected reading, an experienced operator can read the reflectance withhigh precision in a very short
28、 interval. Consequently the time lapsebetween draw-down and reflectance reading should be as short aspossible.NOTE 4Although the method is primarily intended as a rapid method,it obviously can be adapted to measuring the tinting strength in a dry filmof paint. For this an appropriate amount of cobal
29、t drier is added to theblack letdown vehicle during its preparation (see 7.2), and the films areallowed to dry as needed before making the reflectance measurements. Itshould be cautioned that tinting-strength values measured on dry filmsmay differ from those measured on wet films.8. Calculation of T
30、inting Strength8.1 Calculate the tinting strength as follows:TS 5 T!1 2 R!2/2R#s/1 2 R!2/2R#uT!where:TS = tinting strength of test pigment,R= measured reflectance factor (as a decimal),T = assigned tinting strength of standard, usually 100 %,and subscripts“ u” and “s” refer to the test andstandard p
31、igments, respectively.9. Report9.1 Report the following information:9.1.1 Tinting strength rounded to three significant figures,TABLE 1 Examples of Preparation of Black Letdown VehiclesPigment TypeApproximatePigmentDensityPigment, g Clear Vehicle, gBlack LetdownVehicle, gApproximatePVC of FinalPaint
32、, %PredispersedBlack,AgClear Vehicle,BgTitanium dioxide:rutileanatase4.13.83.0003.0002.0002.2501.0001.00020206.80 93.20Lithopone 4.3 5.000 1.220 1.000 35 2.25 250.00Zinc oxide, leaded 5.9 5.000 2.460 1.000 20Zinc oxide 5.6 5.000 2.660 1.000 20White lead 6.8 3.000 0.810 1.000 20ADaniel Products Co. L
33、ampblack F is used for this example.BA 50-50 (by weight) composite vehicle, Aroplaz 1271 and 1278, is the “vehicle used for this example.D27450029.1.2 Identification of the pigment, the reference standard,and the arbitrary assigned value, T, of the tinting strength forthe reference standard. (Also i
34、dentify the vehicle and colorantemployed.), and9.1.3 Name and model number of the color measuringinstrument employed.10. Precision10.1 On the basis of an interlaboratory test of this testmethod in which seven laboratories tested four materialscovering a broad range in tinting strength using five typ
35、es ofcolorimeters, the standard deviation was found to be 1.16within laboratories and 1.72 among laboratories. Based on this,the following criteria should be used for judging the accept-ability of results at the 95% confidence level when the standardis assigned a value of 100:10.1.1 RepeatabilityTwo
36、 results obtained by the sameoperator on the same pigment should be considered suspect ifthey differ by more than 3.3 units.10.1.2 ReproducibilityTwo reported results, obtained byoperators in different laboratories, should be considered sus-pect if they differ by more than 4.9 units.11. Keywords11.1
37、 Muller; tinting strength; white pigmentsASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and th
38、e riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision o
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40、make your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D2745003
