1、Designation: D7786 13Standard Test Method forDetermining Enamel Holdout1This standard is issued under the fixed designation D7786; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses i
2、ndicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard provides a method for determining theholdout characteristics of a primer and topcoat coating appli-cation. A standard topcoat is used to determi
3、ne the absorptioncharacteristics of a primer. Enamel holdout can be measured asa difference in observed gloss of the topcoat over a primer,relative to the gloss of the same topcoat over a non-poroussmooth surface.1.2 The standard is written in the context that the user willbe evaluating the enamel h
4、oldout characteristics of a primer.Alternatively, the standard may be used as a method to evaluatethe enamel holdout characteristics of primer/topcoat systemwhere the primer is constant and different topcoats are used astest paints.1.3 This standard may also be used for evaluation of paintsother tha
5、n primers as the first coat. In this alteration the usercan test the enamel holdout characteristics of a self primedtopcoat, or use of any other type of paint as the primer followedby the use of a standard topcoat.1.4 The values stated in SI units are to be regarded asstandard. No other units of mea
6、surement are included in thisstandard.1.5 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 li
7、mitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D523 Test Method for Specular GlossD823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1640 Test Methods for Drying, Curing, or Film Formationof Organic Coatings at Room Temper
8、atureE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 enamel holdout, nthe ability of a primer/topcoatsystem to retain gloss of the topcoat rela
9、tive to gloss of thetopcoat over a non-porous smooth surface.3.1.2 primer, nan undercoat of paint applied to prepare asurface for final painting.3.1.3 topcoat, na coating, intended as the final coat of afinished system, which has the desired appearance and resis-tance properties as specified by the
10、end user.4. Summary of Test Method4.1 A substrate, preferably a non-porous smooth drawdowncard, is coated using a test primer and allowed to dry. Theprimer-coated substrate is then coated with the standard top-coat and allowed to dry (primed topcoat).4.2 A non-porous smooth substrate is coated using
11、 only thestandard topcoat and allowed to dry (unprimed topcoat).4.3 Gloss measurements are taken over the primed topcoatand also over the unprimed topcoat. The difference in the glossreading between the primed topcoat system and unprimedtopcoat system is an indication of enamel holdout. Smallerdiffe
12、rences indicate better enamel holdout.5. Significance and Use5.1 This standard may be used by paint companies and rawmaterial suppliers to assess the interactions of primers andtopcoats with respect to their ability to provide good enamelholdout. Primer/topcoat systems with the best enamel holdoutwi
13、ll result in desirable gloss in the first coat of topcoatapplication.6. Apparatus6.1 Film Applicator, preferably a drawdown bar, capable ofapplying wet-film thickness of approximately 0.075 mm (3.0mils).1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, M
14、aterials, and Applications and is the direct responsibility ofSubcommittee D01.42 on Architectural Coatings.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 2012. Last previous edition approved in 2012 as D7786 12. DOI:10.1520/D7786-13.2For referenced ASTM standa
15、rds, 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 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
16、19428-2959. United States16.2 If preferred, brush, roller or spray applicators can besubstituted for the drawdown applicators.6.3 Gloss Meter capable of measuring 20 and 60gloss.7. Reagents and Materials7.1 Substrate Desired for TestingThe preferred substrateshould have a uniform flat surface to ena
17、ble paint films to beapplied with the preferred drawdown bar applicator. Unlessotherwise agreed upon, a non-porous smooth drawdown card isused. Other commonly used substrates include: gypsum panel,wood or drawdown cards with non-porous and porous sections.The choice to use an alternative substrate o
18、ften necessitates thechoice of an alternate applicator such as brush, roller or spray.7.2 Standard PaintsThe topcoat will be a mutually agreedupon standard topcoat. Unless otherwise agreed, use a com-mercially available latex topcoat which yields a gloss between40 and 55 when applied in accordance w
19、ith 9.2.8. Hazards8.1 The user of this test method should refer to appropriateMSDS for hazards associated with handling and disposal ofpaint samples or other laboratory items used as specified in thisstandard.9. Procedure9.1 Application of primer (or other primary coating) andtopcoat.9.1.1 Apply the
20、 primer onto the selected substrate using thefilm applicator across the full length of the drawdown card oralternative substrate. Refer to Practices D823, for the proce-dure and information related to the application of films withuniform thickness.9.1.2 Allow the primer to dry in a controlled enviro
21、nmentfor an appropriate period of time for the primer that has beenapplied. Refer to Test Methods D1640 for the procedure andinformation related to drying, curing, or film formation oforganic coatings at room temperature. Report the environmen-tal condition (C, %RH) and dry time interval.9.1.3 Using
22、 a film applicator capable of applying a wet filmthickness of approximately 0.075 mm (3 mils), apply thestandard topcoat on top of the dried primer coat from step9.1.1. Casting the topcoat in a direction perpendicular to theprimer coat will allow the use of a single drawdown bar forboth primer and t
23、opcoat application while ensuring that thedrawdown bar can travel a uniform path across the primer coat(Fig. 1).9.1.4 Allow the topcoat to dry in a controlled environmentfor an appropriate period of time for the topcoat that has beenapplied. Report the environmental condition (C, %RH) anddry time in
24、terval.9.2 Application of standard topcoat to non-porous smoothsurface:9.2.1 Apply the standard topcoat to the non-porous smoothsubstrate using the same film applicator as in section 9.1.3across the full length of the drawdown card. This applicationshould be made at a similar time as the topcoat in
25、step 9.1.3.9.2.2 Allow the topcoat from step 9.2.1 to dry in a con-trolled environment for an appropriate period of time for thetopcoat that has been applied. This environment and dry timeshould be the same as in step 9.1.4. Report the environmentalcondition (C, %RH) and dry time interval.9.3 Gloss
26、measurement:9.3.1 Measure the gloss of the topcoat on both the primer/topcoat card and the unprimed card. Refer to Test MethodD523 for the procedure and information related to measuringgloss.9.3.2 Record the average of three readings from each chart.If the 60 gloss of the unprimed topcoat is greater
27、 than 80 glossunits, use the 20 gloss reading; otherwise use the 60 glossreading.10. Calculation or Interpretation of Results10.1 Variable Definitions:Enamel Holdout (%retained) = 100*GP/GUEnamel Holdout (%difference) = 100*(GUGP)/GUEnamel Holdout (difference) = GUGPwhere:GP= Gloss of primed topcoat
28、GU= Gloss of unprimed topcoat10.2 Users may choose which calculation to use for report-ing enamel holdout, though percent retained is the preferredmethod.11. Report11.1 Substrate system, applicator choice and applicationmethod for primers and topcoats.11.2 Number of coats of topcoat.11.3 Whether tes
29、t paints are used as primer or topcoat.11.4 Identification of standard topcoat or standard primer.11.5 Environmental conditions and dry time intervals.11.6 Angle of gloss measurements (20, 60).11.7 Gloss value of unprimed topcoat.FIG. 1 Diagram of Perpendicular Drawdown TechniqueD7786 13211.8 Calcul
30、ation method and enamel holdout result.12. Precision and Bias312.1 The precision of this test method is based on an interlaboratory study of ASTM D7786, Test Method for Determin-ing Enamel Holdout, conducted in 2012. Each of ten labora-tories tested one topcoat and three different primers for enamel
31、holdout. Every “test result” represents an individual determi-nation and all participants were asked to report five replicatetest results for each analysis. Practice E691 was followed forthe design and analysis of the data; the details are given inASTM Research Report No. RR:D01-1174.12.1.1 Repeatab
32、ility Limit (r)The difference between re-petitive results obtained by the same operator in a givenlaboratory applying the same test method with the sameapparatus under constant operating conditions on identical testmaterial within short intervals of time would in the long run, inthe normal and corre
33、ct operation of the test method, exceed thefollowing values only in one case in 20.12.1.1.1 Repeatability can be interpreted as maximum dif-ference between two results, obtained under repeatabilityconditions, that is accepted as plausible due to random causesunder normal and correct operation of the
34、 test method.12.1.1.2 Repeatability limits are listed in Table 1.12.1.2 Reproducibility Limit (R)The difference betweentwo single and independent results obtained by differentoperators applying the same test method in different laborato-ries using different apparatus on identical test material would
35、,in the long run, in the normal and correct operation of the testmethod, exceed the following values only in one case in 20.12.1.2.1 Reproducibility can be interpreted as maximumdifference between two results, obtained under reproducibilityconditions, that is accepted as plausible due to random caus
36、esunder normal and correct operation of the test method.12.1.2.2 Reproducibility limits are listed in Table 1.12.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.12.1.4 Any judgment in accordance with statements 12.1.1and 12.1.2 would have a
37、n approximate 95 % probability ofbeing correct.12.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.12.3 The precision statement was determined through sta-tistical examination o
38、f 145 results, from ten laboratories, onthree different primers.12.4 To judge the equivalency of two test results, it isrecommended to choose the material closest in characteristicsto the test material.13. Keywords13.1 absorption; enamel holdout; primer; sealer; under-coaterASTM International takes
39、no position respecting 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 respo
40、nsibility.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 addressed
41、 to ASTM International 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 a
42、ddress shown below.This 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
43、), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).3Supporting data have been filed at ASTM International Headquarters and maybe obtained by req
44、uesting Research Report RR:D01-1174. ContactASTM CustomerService at serviceastm.org.TABLE 1 Enamel HoldoutMaterialAverageAXReproducibilityStandardDeviationSrReproducibilityStandardDeviationSRRepeatabilityLimitrReproducibilityLimitRPrimer 1 66.07 2.64 5.03 7.40 14.07Primer 2 101.77 0.65 0.88 1.82 2.46Primer 3 98.81 1.92 2.87 5.39 8.04AThe average of the laboratories calculated averages.D7786 133
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