1、Designation: D2745 00 (Reapproved 2017)Standard Test Method forRelative Tinting Strength of White Pigments by ReflectanceMeasurements1This standard is issued under the fixed designation D2745; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year 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 test method describes the procedure for determin-ing the relative tinting strength of white
3、 pigments by reflec-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 D332 describes a procedure for visual assess-ment of blue-tinted samples.1.3 The values stated in SI units
4、 are to be regarded 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 pract
5、ices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D332 Test Method for Relative Tinting Strength of WhitePigments by Visual ObservationD2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Mea
6、sured ColorCoordinates3. Summary 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
7、paint and the Y tristimulus 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 t
8、est method provides a means 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
9、obtained with a muller do not 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, equippe
10、d with a weight that exerts 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 flexib
11、le spatula having a chromium-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 ve
12、hicle (excluding refined or 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
13、lacquered charts cut to aconvenient 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 Feb. 1, 2017. Published February
14、2017. Originallyapproved in 1968. Last previous edition approved in 2008 as D2745 00 (2008).DOI: 10.1520/D2745-00R17.2For 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
15、 the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established i
16、n the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.7 Color Measuring Instruments, meeting the requirementsof Practice D2244.5.8 Film Applicator50 or 75 mm (2 or 3
17、 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 purchaser and the selle
18、r.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 circle should be 63 mm (21
19、2 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 provide a reflectivity
20、 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 g with the analyticalba
21、lance 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 concentric circles onthe
22、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 concentric circles, mull 25
23、 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 been found satisfactory as
24、 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 ultimatelyintended for prepa
25、ring 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 vehicle on theplate making a c
26、rater 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 reading. Draw downthe sample p
27、aint 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 measuringinstrument, an
28、d 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 isstronger in tinting str
29、ength. 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 interval. Consequently
30、 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 cobalt drier is added to the
31、black 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 Tinting Strength8.1 Calc
32、ulate 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 and standardpigments, respectively.9
33、. 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,gClear Vehicle,gBlack LetdownVehicle,gApproximatePVC of FinalPaint, %PredispersedBlack,AgClea
34、r 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. Lampblack F is used for this
35、 example.BA 50-50 (by weight) composite vehicle, Aroplaz 1271 and 1278, is the “vehicle” used for this example.D2745 00 (2017)29.1.2 Identification of the pigment, the reference standard,and the arbitrary assigned value, T, of the tinting strength forthe reference standard. (Also identify the vehicl
36、e 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 types ofcolorimeters,
37、 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 thestandard is assigned a value of 100:10.1.1 RepeatabilityTwo results obtained
38、 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 muller; tinting
39、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 the riskof infringe
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