ASTM D2805-2018 pdf free download
ASTM D2805-2018 pdf free download.Standard Test Method for Hiding Power of Paints by Reflectometry
1. Scope
1.1 This test method covers the determination, without reference to a material paint standard, of the hiding power of air dry coatings with Y tristimulus values greater than 15 %. With appropriate modification, it can also be used to test baking finishes. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
6. Apparatus and Materials
6.1 Substrates: 6.1.1 Black Glass Panels, minimum size 200 by 200 mm, and approximately 6-mm thick. 6.1.2 Black and White Paper Charts—The surface shall be smooth and level, and impervious to paint liquids. The black area shall have a maximum reflectance of 1 % and the white area a minimum reflectance of 78 %. The white area shall be non-fluorescent, as observed visually under ultra-violet illumination, or determined in accordance with Practice E1247. 6.2 Balance, accurate to 0.1 mg. 6.3 Glass Slides—Round or square plates of thickness similar to that used for microscope specimen slides, with a minimum area of 40 cm 2 . 6.4 Reflectance-Measuring Instrument 5 —One that allows only diffusely reflected, radiant flux to be incident upon the measuring element. It shall employ a photometric system, including source, filters, and receptor, that provides a response closely similar to the product of the spectral luminous effi- ciency function of the CIE standard observer and source C. It shall provide readings to at least the third decimal place and permit estimation to the fourth. 6.5 Template, 6 with a film area approximately 100 cm 2 determined to the nearest tenth. Record the exact value on Line C 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 µm. 6.7 Computer and Software, for solving the relevant Kubelka-Munk equations.
7. Procedure
7.1 General Instructions:7.1.1 Film Application—Make drawdowns manually with a smooth uniform motion, at the rate ofabout 6 cm/s. Hold paper charts flat by a vacuum plate or other suitable device while making drawdowns. 7.1.2 Reflectance Measurements—Measure the reflectance of each test area at a minimum of three locations, reading or estimating to four decimal places and calculating mean values to the same. Place charts over a white surface and black glass over a black surface while measurements are being made. 7.1.3 Record Keeping—Record all data on a copy of the worksheet form specified in Fig. 1. Typical data entries are shown in Fig. 2. 7.1.4 Weight Measurements—Make all weighings to 0.1 mg on the analytical balance. 7.2 Paint density, D—Determine the density in g/mL to four decimal places in accordance with Test Method D1475 and record on Line A of the worksheet (Fig. 1). 7.3 Nonvolatile Content, N—Sandwich 0.3 mL of paint (dispensed with a 1-mL syringe) between two previously weighed slides, squeezing them together so that the paint spreads to a diameter of about 45 mm. Reweigh to obtain the weight of paint sample. Separate the slides, allow the films to dry, and weigh a third time to determine the dry weight. Then calculate the nonvolatile content of the paint as a decimal fraction to four places. Run in duplicate and report the mean value to three decimal places on Line B of the worksheet (Fig. 1). 7.4 Applicator Selection—Make trial drawdowns on black and white charts at clearances of 100, 150, and 200 µm. Allow them to dry overnight and measure their contrast ratios. Based on the results select the best applicator for a contrast ratio of 0.97 6 0.01, which may be one of the trial applicators or one of intermediate clearance. If it seems necessary, make an additional trial drawdown to confirm the correct applicator.
