1、Designation: D2793 99 (Reapproved 2017)Standard Test Method forBlock Resistance of Organic Coatings on Wood PanelSubstrates1This standard is issued under the fixed designation D2793; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、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 determination of the blockresistance of organic coatings on wood and wood-base
3、d panelsubstrates. Block resistance is the ability of a coating to resiststicking to another surface and to resist any change inappearance when it is pressed against that surface for aprolonged period of time.1.2 General methods for determining block resistance areoutlined in Sections 6 and 7. Varia
4、tions inherent in usermaterials and procedures, however, may dictate adjustments tothe general method to improve accuracy. Paragraphs 7.3 and7.4 provide guidelines for tailoring the general procedure to ausers specific application. Paragraph 7.5 offers a rating meth-odology.1.3 Test Method D2091 sho
5、uld be used for the determina-tion of print resistance or pressure mottling of organic coatings,particularly lacquers, applied to wood-based case goods suchas furniture.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 Th
6、is 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 practices and determine the applica-bility of regulatory limitations prior to use.1.6 This internationa
7、l standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committe
8、e.2. Referenced Documents2.1 ASTM Standards:2D2091 Test Method for Print Resistance of Lacquers3. Summary of Test Method3.1 The coatings are prepared for testing in a mannerduplicating production application and curing conditions asnearly as possible on the specified wood substrate. Then a stackof t
9、hese painted substrates is formed and subjected to aspecified pressure and temperature for a sufficient time todevelop any sticking tendencies that exist. The pressure isreleased and the painted surfaces are examined for any signs ofsticking or pressure mottling. If blocking (forming a block bypanel
10、s sticking together) occurs, the material is unsatisfactory.If no sticking or damage to the film surface occurs, the materialis satisfactory.3.2 When the conditions of production finishing are estab-lished and known, the method of application, the substrate, filmthickness, and cure of the film shoul
11、d duplicate these condi-tions as closely as possible. However, some acceleration of thetest may be possible with more severe conditions.4. Significance and Use4.1 Coated wood panel products must be stacked face toface or face to back during warehousing, packaging, andtransportation without the coate
12、d finish sticking (blocking) andbecoming damaged. This test method describes a laboratorymeans of evaluating conditions of blocking using factors ofpressure, heat, time and moisture.4.2 Degrees of hardness or degrees of cure of organiccoatings, or both, can be evaluated using a blocking test.4.3 The
13、 rate of volatile loss (drying speed) of organiccoatings can be evaluated using a blocking test.4.4 The effectiveness of protective packaging materials (slipsheets) for organic coatings on wood substrates can be evalu-ated using a blocking test.1This test method is under the jurisdiction of ASTM Com
14、mittee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.52 on Factory Coated Wood Products.Current edition approved July 1, 2017. Published July 2017. Originally approvedin 1969. Last previous edition approved in 2011 as D2793 99 (2011
15、). DOI:10.1520/D2793-99R17.2For 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 the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100
16、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 in the Decision on Principles for theDevelopment of International Standards, Guides and Rec
17、ommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Apparatus5.1 Hydraulic Press (preferably constant pressure), capableof maintaining the agreed upon stacking pressure.5.2 Rigid Platens, at least 4 in. (100 mm) square, capable ofbeing maintained at th
18、e desired test temperature.6. Test Specimens6.1 For those cases where the intended use conditions arenot established or known, the following specifications or someset of specifications agreed upon between the purchaser andseller apply:6.1.1 The test coating shall be applied by spray to a panel.6.1.2
19、 The panel shall be a piece of 6.4 mm (14 in.) smoothtwo side (S2S) standard hardboard or other thickness and typeof wood substrate.6.1.3 The dry film thickness of pigmented coatings shall be1.5 6 0.2 mils (38 6 5 m), and of clear coatings, shall be 306 5 m (1.2 6 0.2 mils) or other agreed upon film
20、 thickness.Cure of the coating shall be as agreed and should be standard-ized for each coating.NOTE 1Film thickness can be measured by weight differences beforeand after painting, but this requires careful conditioning of the substrateunder standard temperature and humidity conditions prior to each
21、weigh-ing. Film thickness can also be determined by using an aluminum tabalongside the test panel and measuring the film thickness with a standardeddy-current gage or using a steel panel with a magnetic film thicknessgage. Alternatively, on smooth surface boards, a draw down bar applicatorwith known
22、 film thickness delivery may be used.7. Procedure7.1 After an agreed upon time (after sample preparation)under ambient conditions, prepare a stack of six samples asfollows (from bottom to top):(1) one face up,(2) two face down,(3) one face up,(4) two face down.This provides two face-to-face and face
23、-to-back contacts. Ifslipsheeting materials are utilized or are under consideration,include them between the appropriate interfaces.7.2 Preheat the press platens to 49 6 1C (120 6 2F) orother agreed upon temperature. Insert the sample stack into thepress and apply the load for a minimum of 24 h, thr
24、ough rigidpressure platens using one of the following conditions:Class A80 psi 6 4 psi (560 kPa 6 28 kPa)Class B40 psi 6 2 psi (280 kPa 6 14 kPa)Class C20 psi 6 1 psi (140 kPa 6 7 kPa)Class D5 psi 6 0.25 psi (35 kPa 6 1.7 kPa)These classes are arbitrary and merely represent tests ofgreater to lesser
25、 severity depending upon materials and proce-dures of the end user. Other pressures, types of pressure platesor times, or combination thereof, may be used as agreed uponbetween purchaser and seller.7.3 Determination of valid pressures for use in the blockingprocedure is not easy. In practice, pressu
26、res of 20 to 100 psi(140 to 200 kPa) have proven suitable for hardboard substrates:2 to 5 psi (1435 kPa) for solid wood substrates. Where noprocedure exists, approximations may be made using a calcu-lation of production stacking pressure, as follows:DHA1/A2! 3F (1)where:D = board density,H = stack h
27、eight,A1= stack area,A2= support area, andF = safety factor.Support area is difficult to establish precisely. In practice,stacking may be directly on the floor, or support stringers maybe used. As stringers increase stacking pressures substantially,this should be compensated for by use of higher pla
28、tenpressures or by the inclusion of stringer rods in the samplestack.7.4 If the presence of water between substrate surfaces canbe logically anticipated as a result of the manufacturing processor storage conditions, include it in the procedure, as blockingtendencies may be altered. Systematic coated
29、 surface wettingprior to test such as contact with saturated toweling, orconditioning at elevated relative humidity conditions, can beuseful in improving test efficacy.7.5 At test conclusion, open the press and pick up the stackin such a fashion that first the bottom panel, then the next tobottom pa
30、nel, and eventually all the panels are allowed to freefall of their own weight. Sample pairs that do not separate viafree fall will be set aside to be separated by hand. If desired, arating of blocking tendency can be established to differentiatebetween categories. The following designations may be
31、useful:Degree of Blocking Surface DamageA = free fall separation 0 = noneB = slight tap to separate 1 = 50 % damageAlthough “degree of blocking” is a subjective determination,its usefulness in differentiating between variables in a singleevaluation is obvious. Results of experiments conducted overlo
32、ng time periods are of greatest utility if the same rater doesthe evaluation or if control panels are included for reference.Ratings of surface damage could be based upon visual stan-dards to assist the rater and reduce variation between raters.Passing rating generally would be “A-0” or as mutually
33、agreedupon.7.6 Whichever method is chosen or developed, it is stronglyrecommended to incorporate pass-fail controls of knownblocking tendency as a means to establish test validity. If theblocking test under study proves less severe than actualproduction/storage conditions, increases in test temperat
34、ure,platen pressure, or water contact, or a combination thereof, willincrease the severity and vice versa.7.7 Accelerated Procedure to Reduce the Time Period forSimulation of Blocking Conditions Observed in the Field:7.7.1 After an agreed upon period of cooling, the cured,coated boards are placed in
35、 a stack of two or more panelsoriented to provide face to face or face to back contact, or both,depending upon the stacking configuration in use.D2793 99 (2017)27.7.2 As in the Standard Procedure, the panel stack isloaded in a hydraulic press under some experimentally deter-mined temperature, pressu
36、re and time period that has beenfound to correlate with actual experience in use.7.7.2.1 A typical starting point set of conditions is:(1) TemperatureThat of the actual stack in use underworst case (highest temperature) condition, that is, up to 100C(212F),(2) PressureIncreased several fold above th
37、at encoun-tered in use, that is, 50 to 200 psi (350 to 1400 kPa), and(3) TimeAs short a time under test as possible withreasonable correlation, that is, 15 to 60 minutes.7.7.3 Conversely, a set of temperature, pressure, and timeperiod can be experimentally determined that produces noblocking. This c
38、an then be used to establish field stackingprocedures and conditions.7.7.4 Pass or fail criteria at the end of the test is similar to7.3 and 7.4.8. Report8.1 This is a go/no-go test for both face-to-face and face-to-back conditions. In addition to the separate statement ofsatisfactory or not satisfa
39、ctory under both of these conditions,the nature of the failure should be reported. The report shouldalso include the particulars of the test as follows:8.1.1 Type of substrate,8.1.2 Method of application,8.1.3 Curing cycle,8.1.4 Film thickness, and test method used,8.1.5 Temperature, humidity, and p
40、ressure of the wet or dryblocking test,8.1.6 Type of stacking including identification and type ofpackaging material (slip sheets) if any, and8.1.7 Duration of test.9. Precision and Bias9.1 PrecisionBecause this test method is used for a varietyof coating chemistries, substrate stacking orientation
41、andstorage conditions, precision and bias must be determined foreach specific set of test conditions as determined by producerand user.9.2 BiasAs no accepted reference material exists, biascannot be determined.10. Keywords10.1 blocking test; lacquer; organic coating; paint; pressuretest; varnish; wo
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