1、Designation: D5235 13D5235 14Standard Test Method forMicroscopicalMicroscopic Measurement of Dry FilmThickness of Coatings on Wood Products1This standard is issued under the fixed designation D5235; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of 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 covers the measurement of dry film thickness of coatings applied to a smo
3、oth, textured or curved rigidsubstrate of wood or a wood-based product1.2 This test method covers the preparation of wood or wood-based specimens for the purpose of microscopicalmicroscopicmeasurement of dry film thickness.1.3 This test method suggests an interpretationanalysis of dry film thickness
4、 of coatings on wood or wood-based products whenporous substrates are coated.using a microscopic measurement.1.4 This test method suggests an interpretation of dry film thickness of coatings on wood or wood-based products whensubstrate attached or non-attached fibers occur in the dry film.1.4 The va
5、lues stated in either SI units or inch-pound units are to be regarded separately as standard. The values given inparentheses are mathematical conversions to SI units that are provided for information only and are not considered stated in eachsystem may not be exact equivalents; therefore, each syste
6、m shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establis
7、h appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.Some specific hazards statements are given in Section 7 on Hazards.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 dry film thickness, thickness or DFT, nthat layer
8、of the thickness of dried coating above the microscopically visibleboard surface that also comprisesdried, cured coating film on the substrate surface which may include attached fibers but excludesfree fibers that are encapsulated in the layer itself.2.1.2 edge face, nthat part of the specimen that
9、is a plane perpendicular to the surface showing a cross section of the coatingand substrate.2.1.3 soak in, nrefers to a coating on a porous substrate(wood) where the coating does not lie essentially on the surface ofthe wood or wood-based product, but has penetrated into the fiber structure of the w
10、ood or wood-based material.2.1.3.1 DiscussionWood or wood-based products are generally of a porous nature; sometimes exhibiting uniform absorption of coatings. Frequentlyabsorption of coatings is of a nonuniformnon-uniform nature and influenced by localized surface density differences or wood poresi
11、ze. These conditions of coating absorption are commonly referred to as soak in.3. Summary of Test Method3.1 A specimen of coated wood or wood-based product is cut to convenient size and edge polished with sandpaper.face withthe coating film cross-section is prepared by polishing or cutting with a sh
12、arp blade.1 This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.52 on Factory Coated Wood Products.Current edition approved Nov. 1, 2013Dec. 1, 2014. Published December 2013Feb
13、ruary 2015. Originally approved in 1992. Last previous edition approved in 19972013as D5235 97D5235 13. which was withdrawn January 2006 and reinstated in November 2013. DOI: 10.1520/D5235-13.DOI: 10.1520/D5235-14.This document is not an ASTM standard and is intended only to provide the user of an A
14、STM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as publishe
15、d by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 The polishedprepared edge of the specimen is viewed throughimaged by a calibrated microscope imaging system withknown magnificatio
16、n in order to measure dry film thickness.the dry film thickness using an image analysis computer program.3.3 Suggestions regarding interpretation of dry film thickness on porous wood or wood-based material are offered.3.4 Suggestions regarding interpretation of dry film thickness on wood or wood-bas
17、ed material that have attached orencapsulated fibers in the coating are offered.4. Significance and Use4.1 As a base for calibration adjustment or accuracy verification of dry film coating thickness measuring instruments.4.2 The dry film thickness of coatings on wood or wood-based products is specif
18、ied in written product warranties for properdecorative and protective performance of coatings on wood or wood-based products.4.3 The minimum and maximum dry film thickness of coatings is recommended by coating companies for satisfactorydecorative and protective performance on wood or wood-based prod
19、ucts.4.4 The average dry film thickness of coatings on wood or wood-based material may be used by manufacturing companies tocalculate estimate the theoretical cost of applied coatings. By comparison with actual cost, utilization efficiency may be calculated.4.5 The ratio of peakminimum to valleymaxi
20、mum dry film thickness on textured products is used as an indication of coatinguniformity.4.6 Specific coated product requirements may dictate certain film thickness determinations to be made. DiscussionsAgreementbetween buyer and seller may be advisable to accommodate product needs relative to dry
21、film thickness.5. Apparatus5.1 Calibrated Monocular MicroscopeMicroscope with Attached, Digital Camera (see Note 1), equipped with an opticalsystemproviding sufficient resolution of 0.1-mil (2.54-m) dry film thickness. One system consisting of a 16-mm objective and a10-power filar micrometer eyepiec
22、e, resulting in a magnification of at least 100 diameters, has been found satisfactory. Othercombinations of objectives and eyepieces and other magnifications may also be suitable, although magnifications above 200diameters may result in distortion of the viewed cross section.magnification and image
23、 quality in the field of view; generally 100to 200 magnification is sufficient.NOTE 1Certain digital cameras can provided sufficient magnification and image quality of the coating cross-section without a microscope.5.2 Source of Oblique Illumination, for the microscope.5.3 Image Analysis Program, wi
24、th capabilities for lines to be drawn along the coating/substrate interface and the coating surfaceand for calculation of the average distance between these lines on the specimen image.5.4 Microscope Image Calibration Tool.5.5 Cutoff Saw.5.6 Belt or Disc Sander.5.7 C-Type Clamp.5.8 Sharp Utility Kni
25、fe or Razor Blade.6. Materials6.1 200 and 600-Grit Sand Paper.6.2 Mold,Mould, such as a paper cup, aluminum weighing dish, or a 2 in. (50.8 mm)50.8 mm 2 in. or larger diameter plasticpipe that is at least 1 in. (25.4 mm)25.4 mm 1 in. high.6.3 Source of Sanding Adhesive, which is used as encapsulatin
26、g medium such as:6.3.1 Hot Melt Glue,6.3.2 Fast-Cure Acrylic Mounting Kit, andor6.3.3 Epoxy.6.4 Solvent-borne Tint Dispersion, which is compatible with the sanding adhesive.6.5 Mineral Oil.6.6 Automotive Red Transmission Oil.6.7 Zinc Stearate Powder.7. Hazards7.1 Use saws and sanders with goggles, d
27、ust mask, and proper machine safeguards to prevent injury to body limbs.D5235 1427.2 Solvent-based tint dispersions and adhesives may be flammable and contain toxic solvents. See manufacturers instructionsfor use and proper disposal.7. Procedure7.1 Specimen PreparationSelect the area to be measured
28、for coating thickness and remove it from the coated wood orwood-based material by a suitable method. Methods of sawing, core drilling, chiseling etc., can be used. Avoid collection ofsamples near the edges of sheeting material or the ends of boards, particularly those coated in vacuum coaters, unles
29、s defectivecoating application is being investigated. For textured surfaces, areas representative of varying degrees of texture (average,extreme, minimal or non-existent) should be selected. Take care that areas of interest are not damaged. Cutting across wood grainsis preferable in exposure of area
30、 of the interest and must be conducted when a coated rough wood surface is being tested. Inspectionof the surface of interest for excessive damage, as well as preliminary assessment of coating conditions and uniformity ofapplication should be conducted under a microscope. Appropriate areas for coati
31、ng dry film thickness measurements should beselected based on testing purpose.7.1.1 Frequently the purpose of testing is the measurement of the average coating dry film thickness for coating spreadassessment or identification of areas with excessively thick or thin coating dry film thickness.7.2 Spe
32、cimen Surface PreparationTwo methods are described for specimen surface preparation due to the variability in theproperties of wood coatings. Method A is recommended to be used for hard coatings, for example, melamine furniture coating orpolyester coating, which are brittle at room temperature and c
33、ould shatter in contact with a sharp blade. Method B is recommendedfor flexible, exterior finishes, which would smear in contact with sandpaper. Such smearing may mask the appearance of voids orfracture lines in the coating and substrate and may eliminate coating/wood substrate interface details, th
34、ereby increasingmeasurement error.7.3 Specimen Preparation:Method A:7.3.1 Select the desired coated area of a wood or wood-based material that is to be measured for dry film thickness. With thecutoff saw, cut off a sample at least 138.1 mm 112 in. (38.1 mm)in. wide from this area.area for mounting a
35、nd encapsulation incasting resin (Note 2).NOTE 2Some specimens could be satisfactorily prepared and tested without mounting. Mounting may be omitted, if careful microscopic inspectionof the sanded specimen does not show any damage to the area of interest or coating edge distortion.7.3.2 Cut this spe
36、cimen to a length that is at least 12.7 mm 12 in. (12.7 mm)in. less than the inside diameter of the mold tobe used.7.3.3 Place the specimen, with the sample edge to be measured, face down and approximately centered in the mold.7.3.4 Prepare the sanding adhesive according to the manufacturers directi
37、ondirections for use. A dispersed pigment may beadded to the adhesive for better microscopic contrast between the dry film and the adhesive.7.3.5 Pour the sanding adhesive around the sample in the mold and allow to harden according to the manufacturers directions.7.3.6 Remove the mold from the harde
38、ned and encapsulated specimen edge.7.3.7 Using a disc sander, belt sander or 200-grit sandpaper mounted on a glass plate, sand the edge face of the encapsulatedspecimen to be measured until the edge face is relatively smooth. Maintain the edge face of the specimen as flat as possible duringsanding.
39、Avoid heat buildup of the sanding adhesive by intermittent sanding if necessary.7.3.8 Polish the edge face of the rough sanded specimen as follows:7.3.8.1 Mount a piece of 600-grit sandpaper on a flat glass plate. Rub the edge face of the rough sanded specimen over the600-grit sandpaper in one direc
40、tion, then reverse direction by 180 for several more rubs. Zinc stearate powder can be sprinkledon the 600-grit sandpaper or the 600-grit sandpaper can be wetted with mineral oil to produce a highly polished edge face free ofscratches.7.3.8.2 Some laboratories find that a mold for the specimen encap
41、sulation with sanding adhesive is not necessary. In this casetwo specimens are prepared with the cutoff saw. The sanding adhesive after proper mixing is generously applied to the coated faceof each specimen, the specimens are placed together and a C-clamp is used to squeeze out some of the sanding a
42、dhesive. TheC-clamp is not removed until sanding adhesive has hardened.8.1.9 To improve the microscopic contrast between the coating and the wood or wood-based product, wipe a light film ofmineral oil or automotive red transmission oil across the polished edge face with a clean cotton rag or equival
43、ent.8.1.10 Some coatings and substrates are hard enough that encapsulation with a sanding adhesive is not necessary. Although inall cases, use of the encapsulating sanding adhesive will lead to the sharpest microscopic edge face and the highest degree ofaccuracy.8.1.11 Some laboratories find that a
44、mold for the specimen encapsulation with sanding adhesive is not necessary. In this casetwo specimens are prepared with the cut off saw. The sanding adhesive after proper mixing is generously applied to the coated faceof each specimen, the specimens are placed together and a C-clamp is used to squee
45、ze out some of the sanding adhesive. TheC-clamp is not removed until the sanding adhesive has hardened.7.4 Method B:D5235 1437.4.1 Select the desired area of coated wood or wood-based material that is to be measured for dry film thickness and obtaina suitable sample using the cutoff saw or other app
46、ropriate tool cut off a suitable sample. There is a handling advantage if thesample to be tested has a rectangular shape.7.4.2 To aid in the preparation of the cross-section for testing, the sample must be additionally cut at an acute angle 70 to 85with respect to the coated surface (Fig. 1). Then,
47、using a sharp blade in a slow continuous movement, make a shallow cut parallelto the edge face with the coating cross-section, cutting from the coating surface into the substrate to remove any loose wood fibersand/or damaged coating from the area of interest. Inspect the obtained cross-section under
48、 microscope for surface quality. A cleanview of the cellular wood structure and clear focus along the coating cross-section with well-visible interface details is a goodindication of proper surface preparation. The cutting direction depends on the wood grains and coating properties.7.5 Measurement f
49、or the Microscopic Dry Film Thickness Measurement From the Image of the Polished Edge Face of theSpecimen:7.5.1 Place the polished or clean cut edge face under the microscope lens.7.5.2 Adjust the illuminating light at a convenient oblique angle. Proper light angle adjustment is helpful in obtaining goodcontrast along the coating surface edge, inter-coat boundaries, and coating/wood interface. This is particularly important whenmeasuring transparent coating DFT.7.5.3 Adjust magnification. Generally 100 magnification is sufficient for coating DFT above
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