ASTM D6686-2001 Standard Test Method for Evaluation of Tannin Stain Resistance of Coatings《覆层抗丹宁着色评定的标准试验方法》.pdf

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1、Designation: D 6686 01Standard Test Method forEvaluation of Tannin Stain Resistance of Coatings1This standard is issued under the fixed designation D 6686; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.

2、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 is an accelerated procedure to deter-mine the effectiveness of latex coatings at preventing themigration of tannin

3、stains from wood substrates.1.2 The values in SI units are to be regarded as the standard.The values in parenthesis are for information only.1.3 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

4、to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1475 Test Method For Density of Liquid Coatings, Inks,and Related Products2D 4585 Practice for Testing Water Resistance of Coating

5、sUsing Controlled Condensation2D 5068 Practice for Preparation of Paint Brushes for Evalu-ation33. Terminology3.1 Definitions:3.1.1 tannin stain resistancethe ability of a coating toprevent the migration of tannins or other wood-based chro-mophores to the surface of a film.4. Summary of Test Method4

6、.1 This test method utilizes a condensation test chamber todetermine the tannin stain resistance of latex paints. The testpaints are applied to substrates that contain tannin extractivesand are placed on or in the test chamber. CIELAB L* and b*values as well as subjective ratings are recorded after

7、exposure.5. Significance and Use5.1 Tannins and other chromophoric extractives are natu-rally occurring materials in wood and wood-based substrates.Tannins are prevalent to a high degree in cedar, redwood, oakand to a lesser degree in white and yellow pine. Tannins arealso present in varying amounts

8、 in wood composition products.These extractives are solubilized and darkened in color byaqueous coatings, resulting in unsightly yellow or browndiscolorations. This test method is designed to show therelative ability of paints to prevent tannin bleed-through.Typically cedar or redwood panels are use

9、d for this test.6. Apparatus6.1 Test Chamber, as described in Practice D 4585.6.2 Test Substrate, 2.4 by 19.2 cm (6 by 48 in.) substrate orof a size agreed upon by the purchaser and seller of the coatingbeing tested.6.3 Paint Brush, nylon/polyester brush of good quality.6.4 Spectrophotometer.6.5 Ele

10、ctronic Balance.6.6 Conditioned Room, at 18 to 29.5C (65 to 85F) and 40to 60 % relative humidity.7. Reagents and Materials7.1 Wood PanelsSuch as cedar, redwood, oak, white pine,yellow pine or other substrate as agreed upon between thepurchaser and the seller of the coating being tested.7.2 Control P

11、aintAn agreed-upon paint of known tanninstain resistance.7.3 Test PaintsSince there are no standard panels, photo-graphs, or paints for this test method, an agreed-upon controlpaint (7.2) should be included as one of the test paints.8. Procedure8.1 Choose a substrate with a consistent grain pattern.

12、Patterns vary greatly from panel to panel, so try to select aboard that has consistent wood grain across the length of thesubstrate. Results may vary from panel to panel because ofdifferent growth rates, grain angles, colors and species ofwood. If necessary, panels may be sanded to remove raisedgrai

13、n. Substrates with areas of rough spots should be avoided,as they will bleed through more readily. Divide substrate intostrips at least 2.4 cm (6 in.) wide or as agreed upon between thepurchaser and the seller and label the back of each test areawith paint designation. The control paint should be pl

14、aced nearthe middle of the panel.8.2 Prepare the cabinet as described in Practice D 4585.8.3 Prepare paint brush as described in Practice D 5068.8.4 Prime all edges of the panels with an appropriate primer1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,

15、 Materials, and Applictions and is the direct responsibility ofSubcommittee D01.42 on Architectural Coatings.Current edition approved June 10, 2001. Published August 2001.2Annual Book of ASTM Standards, Vol 06.01.3Annual Book of ASTM Standards, Vol 06.02.1Copyright ASTM, 100 Barr Harbor Drive, West

16、Conshohocken, PA 19428-2959, United States.and allow to dry according to manufacturers recommenda-tions. The backside of the panels must also be primed if thepanels are to be placed fully inside the chamber.8.5 Measure the density of the test paint in accordance withTest Method D 1475, and then usin

17、g a brush, apply sufficientweight of test paints to achieve the desired spreading rate.Since dry time is critical, paints should be applied as quickly aspossible, so that the average dry time is as close to the specifieddry time as possible for each test paint. If a second coat (selfprimed) is to be

18、 applied, allow the first coat to dry in theconditioned room for four h (dry time may affect results) or asagreed upon between the purchaser and seller. If appropriate,apply second coat or topcoat over the entire substrate withenough grams to achieve the desired spread rate. Stain block-ing is highl

19、y dependent of film thickness; therefore, it isessential that the test paints be weighed on accurately, particu-larly for small test areas. The amount of paint in grams requiredfor a specific spread rate can be determined from the followingequation:g 5 A*W!/S!*3.15where:A = area, square inches,W = w

20、eight per gallon, lb./gal, andS = spreading rate, square feet/gal.Or the following metric equation:g 5 Am*D!/Sm!*1000where:Am= area, square meters,D = density, g/mL or kg/L, andSm= spreading rate, square meters/L.8.6 Allow the panels to dry in the conditioned room for 246 1 h (dry time may affect re

21、sults) or as agreed upon betweenthe purchaser and seller. Immediately place the panels on thechamber with the painted sides facing toward the humidity orplace backprimed panels fully inside the chamber if agreedupon between the purchaser and seller. All panels should be runsimilarly. If the panels a

22、re placed on the chamber, fill all spacesin the specimen rack with test boards or blanks. Close allcracks between boards to prevent water vapor loss and tem-perature variation. Larger cracks may be closed with tape ormetal strips. If the panels are placed inside the chamber, makesure panels are plac

23、ed at an angle to avoid water spotting andrun off onto the test areas.8.7 Adjust the thermostat to maintain the desired tempera-ture of the saturated air and water vapor mixture. Cabinettemperature of 39C (100F) is suggested. To ensure adequatecondensation on face down panels, maintain at least a 11

24、C(20F) temperature differential between the room and theinside of the chamber.8.8 After 16 6 1 h, or an exposure time agreed uponbetween the purchaser and seller, carefully remove the panelsand allow to dry for 24 h.8.9 Quantitatively rate each paint using the ASTM ScoringSystem 0-10 with 10 being n

25、o tannin stain and 0 a severe stain.8.10 Check CIELAB values using a spectrophotometer.Report L* and b* values. In this test b* values are mostimportant. Lower b* values generally indicate better tanninblock resistance. Higher b* values indicate a yellower orbrowner color. L* values, measuring white

26、ness versus dark-ness, are also important. Significant differences in either L* orb* values is 0.5 units. Five readings per test area should betaken, ranging from the top portion to the bottom part, andaveraged together. The average of multiple measurementsshould minimize differences in grain patter

27、n. Readings shouldnot be taken over any obvious defect which is not a truereflection of the test area, such as a knot or any other defect.9. Report9.1 Report the following information:9.1.1 Substrates used, test paints, topcoat, spreading rates,dry time of first coat, dry time of topcoat, vapor temp

28、eratureand exposure time of topcoated panel to humidity. Report if thepanels were placed face down or fully inside the cabinet.9.1.2 Subjective results based on 0-10 scale.9.1.3 L* and b* values and specify both illuminant andstandard observer.10. Precision and Bias10.1 It is not possible to specify

29、 the precision and bias inTest Method D 6686 for measuring the tannin stain resistanceof coatings because of the varying degree of tannin stainspresent in the test substrates.11. Keywords11.1 stain blocking; tannin stain; wood extractives; woodstainThe American Society for Testing and Materials take

30、s no position respecting the validity of any patent rights asserted in connectionwith any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any suchpatent rights, and the risk of infringement of such rights, are entirely their own res

31、ponsibility.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 of this standard or for additional standardsand should be address

32、ed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsibletechnical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make yourviews known to the ASTM Committee on Standards, at the address shown

33、 below.This standard is copyrighted by ASTM, 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 above address or at610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website (www.astm.org).D 66862