1、Designation: D 2793 99 (Reapproved 2005)Standard Test Method forBlock Resistance of Organic Coatings on Wood PanelSubstrates1This standard is issued under the fixed designation D 2793; 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 (e) 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-b
3、ased 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. Va
4、riations 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 D 2091
5、 should 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.
6、5 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 to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Doc
7、uments2.1 ASTM Standards:2D 2091 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 these painted subst
8、rates 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 bypanels sticking togethe
9、r) 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 should duplicate these
10、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 coated finish sticking
11、(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 rate of volatile
12、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.5. Apparatus5.1 Hydraulic Press (preferably constant pressure), ca-pable
13、of maintaining the agreed upon stacking pressure.5.2 Rigid Platens, at least 4 in. (100 mm) square, capable ofbeing maintained at the desired test temperature.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct
14、 responsibility ofSubcommittee D01.52 on Factory Coated Wood Products.Current edition approved May 15, 2005. Published June 2005. Originallyapproved in 1969. Last previous edition approved in 1999 as D 2793 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
15、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Test Specimens6.1 For those cases
16、 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 The panel shall be a piece of 6.4 mm (14 in.) smoothtwo side (
17、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 5m(1.2 6 0.2 mils) or other agreed upon film thickness.Cure of the coating shall be as agreed and should be s
18、tandard-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 weigh-ing. Film thickness can also be determined by using an alum
19、inum 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 film thickness delivery may be used.7. Procedure7.1 After an agr
20、eed 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-to-back contacts. Ifslipsheeting materials are utilized or are u
21、nder 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, through rigidpressure platens using one of the following conditions:
22、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 severity depending upon materials and proce-dures of the end use
23、r. 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, pressures of 20 to 100 psi(140 to 200 kPa) have proven suitable for har
24、dboard 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! 3 F (1)where:D = board density,H = stack height,A1= stack area,A2= support area, andF = safety factor.Supp
25、ort 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 platenpressures or by the inclusion of stringer rods in the samples
26、tack.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 surface wettingprior to test such as contact with saturated tow
27、eling, 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 panel, and eventually all the panels are allowed to freefall of th
28、eir 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 useful:Degree of Blocking Surface DamageA = free fall separation
29、 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 overlong time periods are of greatest utility if the same rater doesth
30、e 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 agreedupon.7.6 Whichever method is chosen or developed, it is st
31、ronglyrecommended 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 temperature,platen pressure, or water contact, or a combination thereof,
32、 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 a stack of two or more panelsoriented to provide face to face
33、or face to back contact, or both,depending upon the stacking configuration in use.7.7.2 As in the Standard Procedure, the panel stack isloaded in a hydraulic press under some experimentally deter-mined temperature, pressure and time period that has beenfound to correlate with actual experience in us
34、e.7.7.2.1 A typical starting point set of conditions is:D 2793 99 (2005)2(1) TemperatureThat of the actual stack in use underworst case (highest temperature) condition, that is, up to 100C(212F),(2) PressureIncreased several fold above that encoun-tered in use, that is, 50 to 200 psi (350 to 1400 kP
35、a), 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 can then be used to establish field stackingprocedures and cond
36、itions.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 satisfactory under both of these conditions,the nature of the failure
37、 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 pressure of the wet or dryblocking test,8.1.6 Type of stacking
38、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 andstorage conditions, precision and bias must be determined f
39、oreach specific set of test conditions as determined by producerand user.9.2 Bias-As no accepted reference material exists, biascannot be determined.10. Keywords10.1 blocking test; lacquer; organic coating; paint; pressuretest; varnish; wood substratesASTM International takes no position respecting
40、the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard
41、 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 addressed to ASTM International
42、Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This
43、 standard is copyrighted by ASTM International, 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 aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 2793 99 (2005)3
