1、Designation: D7786 12Standard 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).6.2 If preferred, brush, roller or spray applicators can besubstituted for the drawdown applicato
14、rs.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.42 on Architectural Coatings.Current edition approved Feb. 1, 2012. Published February 2012. DOI: 10.1520/D778612.2For re
15、ferenced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, W
16、est Conshohocken, PA 19428-2959, United States.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 enable paint films to beapplied with the preferred drawdown bar applicator. Unless
17、otherwise 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 often necessitates thechoice of an alternate applicator such as brush, roller or
18、 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 with 9.2.8. Hazards8.1 The user of this test method should refer to appropriateM
19、SDS 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 primer onto the selected substrate using thefilm applicator across the full le
20、ngth 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 environmentfor an appropriate period of time for the primer that has beenapplied. Ref
21、er 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 a film applicator capable of applying a wet filmthickness of approximately 0.0
22、75 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 topcoat application while ensuring that thedrawdown bar can travel a uniform pat
23、h 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 interval.9.2 Application of standard topcoat to non-porous smoothsurface:9.2.1 Ap
24、ply 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 step 9.1.3.9.2.2 Allow the topcoat from step 9.2.1 to dry in a con-trolled envi
25、ronment 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 measurement:9.3.1 Measure the gloss of the topcoat on both the primer/topcoat c
26、ard 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 than 80 glossunits, use the 20 gloss reading; otherwise use the 60 glossreadin
27、g.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 topcoatGU= Gloss of unprimed topcoat10.2 Users may choose which calculation to use for
28、 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 test paints are used as primer or topcoat.11.4 Identification of standard topcoat
29、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.11.8 Calculation method and enamel holdout result.12. Precision and Bias312.1 The precision of this test method is based on asingle-laboratory study
30、of Test Method D7786, Test Methodfor Determining Enamel Holdout, conducted in 2011. Thelaboratory tested three different primers, paired with a singlesemigloss topcoat. Every “test result” reported represents theaverage of three individual determinations. Five test results3Supporting data have been
31、filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D01-1161.FIG. 1 Diagram of Perpendicular Drawdown TechniqueD7786 122were reported for each material combination. Except for theuse of only a single laboratory, Practice E691 was followed forthe design and an
32、alysis of the data; the details are given inASTM Research Report No. D011161.12.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference b
33、etween two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.12.1.1.1 Repeatability limits are listed in Table 1 and Table2.12.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by mo
34、re than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.12.1.2.1 Reproducibility limits cannot be determined from asingle-laborato
35、ry study.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 normally have an approximate 95 % prob-ability of being correct, however the precision statistics ob-tained
36、 in this ILS must not be treated as exact mathematicalquantities which are applicable to all circumstances and uses.The limited number of materials tested and the use of data fromjust a single reporting laboratory results guarantees that therewill be times when differences greater than predicted by
37、theILS results will arise, sometimes with considerably greater orsmall frequency than the 95 % probability limit would imply.The repeatability limit and the reproducibility limit should beconsidered as general guides, and the associated probability of95 % as only a rough indicator of what can be exp
38、ected.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 of 40 results from one laboratory; threepr
39、imers coated with the same semigloss topcoat comparedagainst the semigloss topcoat on a nonporous substrate withoutprimer.12.3.1 To judge the equivalency of two test results, it isrecommended to choose the material closest in characteristicsto the test material.12.4 The following test method details
40、 are reported for thesingle-laboratory study.12.4.1 All films were cast using a 3 mil Bird drawdownapplicator on smooth nonporous drawdown cards (LenetaForm WB). A vacuum plate was used to secure the drawdowncharts.12.4.2 One coat of topcoat was applied.12.4.3 The test paints are identified as Test
41、Primer.12.4.4 The standard topcoat is identified as SemiglossTopcoat.12.4.5 All coatings were applied in a constant temperatureroom with set point conditions of 25C and 50%RH. Primercoats were dried 2 h. Topcoat dry time interval is seven days.13. Keywords13.1 absorption; enamel holdout; primer; sea
42、ler;under-coaterTABLE 1 60 Gloss 7 Day (Gloss Units)Test PrimerStandardTopcoatAverageRepeatabilityStandardDeviationRepeatabilityLimitx Sr rNone SemiglossTopcoatA51.88 0.51 1.43Flat TopcoatBSemiglossTopcoat37.76 0.57 1.59Primer ACSemiglossTopcoat50.72 0.83 2.33Primer BDSemiglossTopcoat49.16 0.86 2.41
43、ACommercially available water-based acrylic interior semigloss topcoat.BCommercially available water-based acrylic interior flat topcoat.CCommercially available water-based styrene acrylic interior primer-sealer.DCommercially available water-based styrene acrylic interior-exterior primer-sealer.TABL
44、E 2 Enamel Holdout 7 Day, 60 Gloss RetainedTest PrimerStandardTopcoatAverageRepeatabilityStandardDeviationRepeatabilityLimitx Sr rNone SemiglossTopcoat100.00 0.99 2.76Flat Topcoat SemiglossTopcoat72.78 1.09 3.06Primer A SemiglossTopcoat97.76 1.60 4.49Primer B SemiglossTopcoat94.76 1.66 4.66D7786 123
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48、ee on Standards, at the address 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), 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/).D7786 124
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