1、Designation: D7835/D7835M 13Standard Test Method forDetermining the Solvent Resistance of an Organic Coatingusing a Mechanical Rubbing Machine1This standard is issued under the fixed designation D7835/D7835M; the number immediately following the designation indicates theyear of original adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a mechanical rub method forassessing the solvent resista
3、nce of an organic coating thatchemically and/or physically changes during the curing pro-cess. This technique can be used in the laboratory, in the field,or in the fabricating shop.1.2 This test method does not specify the solvent, number ofdouble rubs, or expected test results.1.3 The values stated
4、 in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This
5、 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 Documents
6、2.1 ASTM Standards:2D740 Specification for Methyl Ethyl KetoneD4138 Practices for Measurement of Dry Film Thickness ofProtective Coating Systems by Destructive, Cross-Sectioning MeansD5402 Practice for Assessing the Solvent Resistance ofOrganic Coatings Using Solvent RubsD5796 Test Method for Measur
7、ement of Dry Film Thicknessof Thin-Film Coil-Coated Systems by Destructive MeansUsing a Boring DeviceD6132 Test Method for Nondestructive Measurement of DryFilm Thickness of Applied Organic Coatings Using anUltrasonic GageD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagne
8、tic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to Non-Ferrous Metals3. Terminology3.1 Definitions:3.1.1 double rub, none complete forward and backwardmotion over a coated surface under specific conditions, whichare characterized by the force applied normal to
9、the surface, thelength of travel, and rate of speed.4. Summary of Test Method4.1 An automated machine is used to test the solventresistance of a coating by rubbing a cloth saturated with thesolvent across the coating and counting the number of strokes(double rubs) to coating break-through or failure
10、.5. Significance and Use5.1 Many coatings used in the coil coating and otherindustries achieve a degree of solvent resistance after they haveexperienced a bake condition characterized by exposure toelevated temperatures in an oven over time. Insufficient bake,or occasionally over bake, may affect th
11、e intended chemicalbonds or physical curing of the film and result in reducedsolvent resistance.5.2 The mechanical rubbing machine provides consistentstroke length, rate, pressure, and contact area that are notsubject to variables such as human fatigue (see PracticeD5402).5.3 Factors other than bake
12、 can influence degree of solventresistance of a coated surface. Paint film chemistry andcomposition, surface preparation, oven dwell time, oven airvelocity, ambient oven temperature, oven profiling, filmthickness, etc., all are influential. The test solvent used in therub machine has a significant e
13、ffect on the number of doublerubs measured. Common solvents used for these tests includeMethyl Ethyl Ketone (MEK), Methyl Isobutyl Ketone (MIBK),and IsopropylAlcohol to name a few. The specific solvent to beused and the umber of double rubs to be achieved should be1This test method is under the juri
14、sdiction of ASTM Committee on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved July 1, 2013. Published August 2013. DOI: 10.1520/D7835/D7835M-132For referenced ASTM standards, visit the ASTM we
15、bsite, 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 19428-2959. United Sta
16、tes1agreed upon between manufacturer and user for any givencoating system, thickness, and application.6. Apparatus6.1 Solvent Rub Machinewith operator instructions.6.1.1 The machine may be any suitable device that drives amechanical finger through double rubs across the same path ona coated surface
17、and has the following characteristics (see Fig.1).6.1.1.1 The mechanical finger must have a flat, smooth,circular surface 1.6 6 0.2 cm 0.625 6 0.08 in. diameter.6.1.1.2 A weighted block must apply 3000 6 50gofpressure to the mechanical finger.6.1.1.3 Disposable cheesecloth, as specified below, is at
18、-tached to the contact surface of the finger.6.1.1.4 There must be some means of maintaining constantsaturation of the cheesecloth, typically by a solvent reservoir.6.1.1.5 The double rub (stroke) length must be 20 6 2cm86 0.8 in. (one direction) at a minimum rate of 60 andmaximum of 100 double rubs
19、 per minute.6.1.1.6 The number of double strokes must be automaticallycounted (up or down) and displayed by the machine.7. Reagents and Materials7.1 Methyl Ethyl Ketone (MEK), conforming to Specifica-tion D740.7.2 Other Solvents, as specified by the coating manufactureror user.7.3 100 % Cotton Chees
20、ecloth, mesh grade 28 by 24, orother mutually agreed upon cloth.8. Sampling, Test Specimens, and Test Units8.1 Obtain representative, coated, flat panels, and cut thepanels to an appropriate size for the test machine. If possible,use a panel of sufficient length to allow a 200 mm 8 in. longtest surf
21、ace by 25 mm 1 in. width. The long dimension mustbe parallel to the rolling (longitudinal) direction of the coil forcoil coatings.8.2 Measure the dry film thickness of the coating on theselected panel in accordance with standards D4138, D5796,D6132,orD7091 to ensure that the coating meets thicknessr
22、equirements.8.3 For items that may have varied coating thickness andcure across the item (for example, across a coil of coatedmetal), it is recommended that samples representing thatvariation be collected.9. Preparation of Apparatus9.1 Prepare in accordance with the manufacturers instruc-tions.9.2 A
23、djust the machine rub or stroke rate to the desiredvalue. For coil coatings, this would be as close as possible to100 double rubs per minute, consistent with the machinecapability, and no less than 60 double rubs per minuteregardless of coating type.10. Calibration and Standardization10.1 Standardiz
24、e and/or calibrate the rub machine in accor-dance with the machine manufacturers instructions.11. Procedure11.1 Select the appropriate solvent for the test and be surethat the solvent reservoir is filled as recommended by the rubmachine manufacturer.11.2 Fold the cheesecloth into a pad of double thi
25、ckness, cutto fit over the mechanical finger, and then secure into place inaccordance with the manufacturers recommendations.11.3 Clamp the panel to be tested into position according tothe surface to be tested with the long dimension parallel to therubbing direction of the machine (and the rolling d
26、irection forcoil coatings) and in accordance with the machine manufac-turers recommendations.11.4 Set the machine counter to the desired number of rubs,and place the mechanical finger with cheesecloth in position onthe test panel. Be sure the cheesecloth is saturated with solventfrom the reservoir.1
27、1.5 Start the machine.11.6 The test may be run in two different ways as agreedupon between producer and user: (1) the machine is allowed torun for the set number of counts as agreed upon betweenproducer and user, and the coating is inspected for visiblesubstrate (coating break-through) or failure; (
28、2) the machine isallowed to run until the operator observes visible substrate(coating break-through) and the number of double rubs on themachine counter is recorded (or subtracted from the originalsetting if counting down). In the first method, the result is passor fail, and in the second, a numeric
29、al result is recorded. Thesecond method may be more useful for research or cases wherecomparison of continuous data is desired.FIG. 1 Example of a Mechanical Rubbing MachineD7835/D7835M 13211.7 If it is desirable to disregard visible substrate (coatingbreak-through) within 13 mm 0.5 in. either end o
30、f the rubsurface (sometimes referred to as heel-break), such a definitionmust be agreed upon between producer and user.11.8 If it is desirable to change or expose fresh cheeseclothsurface at a specified double rub interval (for example, every25 double rubs) such a procedure must be agreed upon betwe
31、enproducer and user.12. Report12.1 Report the following information as a minimum:12.1.1 Identity of the machine used including model num-ber.12.1.2 Any machine parameters that deviate from thosespecified in Section 6.12.1.3 Identity of the coated sample tested.12.1.4 The solvent used.12.1.5 The dry
32、film thickness of the coating prior to testing.12.1.6 The number of double rubs tested and agreed uponbetween producer and user and the respective pass or failresult, or12.1.7 The number of double rubs at which coating failureas defined by producer and user occurred. If no failure occurredat some ma
33、ximum test limit, report as total double rubs tested(for example, 100 or 100+).13. Precision and Bias13.1 The precision for this test method has not beendetermined.14. Keywords14.1 coil coating; cure; solvent rubsASTM International takes no position respecting the validity of any patent rights asser
34、ted 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 is subject to revision at any time by
35、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 Headquarters. Your comments will receiv
36、e 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 standard is copyrighted by ASTM Intern
37、ational, 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/).D7835/D7835M 133
