1、ASTM D2693 88=0759530 002b03 b W/+o4 74(lb Designation:D 2691-88 AMERICAN SOCIETY FOR TESTINQ AND MATERIALS 1916 Race SI.,Philadelphia,Pa.9103 Reprinted from the Annual Book of ASTM Standards,Copyright ASTM If not listed in the current comb!ned Index,will appear in the next edition.Standard Test Met
2、hods for Microscopical Measurement of Dry Film Thickness of Coatings on Wood Products1s2 This standard is issued under the fixed designation D 2691;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of lasf revision.A number i
3、n parentheses indicafes the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope 1.1.These test methods cover the measurement of film thickness of dried coatings applied to a plane rigid substrate of wood or a wood-base material.
4、These test methods apply to both opaque and clear coatings.They are not recom-mended for metal or glass substrates.Test Method A uses a razor blade and Test Method B a microtome for cross sectioning.1.2 This standard may involve hazardous materials,oper-ations,and equipment.This standard does not pu
5、rport to address all o f the safety problems associated with its use.It is the responsibility o f the user o f this standard to establish appropriate safety and health practices and determine the applicability o f regulatory limitations prior to use.2.Significance and Use 2.1 This test method provid
6、es a precise,quantitative measurement of the thickness of a dried coating.It may be used for quality control or monitoring of the production of coated wood products.3.Apparatus 3.1 Calibrated Monocular Compound Microscope,equipped with an optical system sufficient to provide sharp resolution of the
7、cross section to be examined.One system,consisting of a 16-mm objective and a 10-power filar micrometer eyepiece,resulting in a magnification of approx-imately 100 diameters,has been found satisfactory.Other combinations of objectives and eyepieces and other magnifi-cations may also be suithble,alth
8、ough magnifications above 200 diameters may result in distortion of the viewed cross section.3.2 Tool for Extracting Test Specimens-The tool may be similar in design to an ordinary cork borer,except that it shall be made of thicker walled tubing,hard enough to hold a keen cutting edge,and be fitted
9、with a head suitable for pounding with a hammer(Fig.i).A leather punch has been found satisfactory for this use.The tool shall make a circular cut approximately Y2 in.(12.7 mm)in diameter and 1/1 3 in.(3.2 mm)deep through the coating and into the substrate.A sidewise movement of the punch while firm
10、ly embedded in the substrate wiil dislodge the specimen and allow its Punch V/1 Push Rad(fell-lipped)FIG.1 One Type of Tool for Extracting Coated Wood Specimens removal intact within the punch.3.3 Source o f Oblique Illumination,3.4 Hand Microtome(Method B).4.Test Specimens 4.1 Specimens for microsc
11、opical measurement shall be extracted from the punch tool by means of a push rod inserted through the hollow shaft of its tube.The end of the push rod should be tipped with felt or other soft material so that the coated surface of the disk will not be damaged during extraction.5.Procedure 5.1 Prepar
12、e disks for microscopical examination and meas-urement by either Method A or Method B.Either method of preparation will expose a cross section of coating and sub-sfrate,including the extremes in film thickness resulting from variations in the wood surface or method of application.5.2 Method A,Cross
13、Sectioning with Razor Blade-With a sharp razor blade carefully slice away parallel to the coated surface the substrate adhering to the coating until the disk is approximately/I6 in.(1.6 mm)thick.Place the disk coated face down on a smooth,hard surface and cut in half by means of a slicing stroke wit
14、h a fresh razor blade(Fig.2).Cut in a direction perpendicular to the grain of the wood substrate and at right angles to the coated surface.5.3 Method B,Cross Sectioning with Microtome:5.3.1 With a sharp razor blade carefully slice away parallel to the coated surface the substrate adhering to the coa
15、ting until the disk is approximately/I6 in.(I.6 mm)thick.-5.3.2 Embed the thinned disk in molten paraffin3 which is These test methods are under the jurisdiction of ASTM Committee D-1 on Painf and Related Coatings and Materials and are the direct responsibility of Subcommittee W1.52 on Factory-Coate
16、d Wood Products.Current edition approved March 29,1988.Published May 1988.Originally published as D 2691-68.Last previous edition D 2691-70(1981).*This test method is presently under study for revision or replacement with an improved microscopical film thickness method.Paraplast,available from Fischer Scientific,191 South Gulph Road,P.O.Box J,King of Pnissia,PA 19406 melting point about 50 to 6VC,has been found satisfactory for this purpose.For clear films the addition of 0.5 g of Indigo to 200
