1、Designation: D968 15Standard Test Methods forAbrasion Resistance of Organic Coatings by FallingAbrasive1This standard is issued under the fixed designation D968; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover the determinatio
3、n of theresistance of organic coatings to abrasion produced by abrasivefalling onto coatings applied to a plane rigid surface, such as ametal or glass panel.1.2 Two test methods based on different abrasives arecovered as follows:SectionsMethod AFalling Sand Abrasion Test 613Method BFalling Silicon C
4、arbide Abrasion Test 14211.3 These methods should be restricted to testing in onlyone laboratory when numerical values are used because of thepoor reproducibility of the methods (see 13.1.2 and 21.1.2).Interlaboratory agreement is improved significantly when rank-ing is used in place of numerical va
5、lues.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appro
6、priate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1005 Test Method for Measurement of Dry-Fil
7、m Thick-ness of Organic Coatings Using MicrometersD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to Non-Ferrous MetalsE11 Specification for Woven Wire Test Sieve Cloth and TestSieves
8、2.2 Other Standards:ANSI B74.12 Specifications for the Size of Abrasive Grain Grinding Wheels, Polishing and General IndustrialUses3FEPA Standard 42-2:2006 Grains of Fused AluminumOxide, Silicon Carbide and other Abrasive Materials forBonded Abrasives and for General Applications Mi-crogrits F230 to
9、 F200043. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 abrasion resistance, nthe amount of abrasive re-quired to wear through a unit film thickness of the coating.4. Summary of Test Method4.1 Abrasive is allowed to fall from a specified heightthrough a guide tube onto a coated
10、 panel until the substratebecomes visible. The amount of abrasive per unit film thick-ness is reported as the abrasion resistance of the coating on thepanel. Silica sand or silicon carbide may be used, as specified.5. Significance and Use5.1 Silica sand produces a slower rate of abrasion fororganic
11、coatings than that provided by silicon carbide. Forsome types of coatings, it may also provide greater differen-tiation.5.2 The abrasion resistance scales produced by the twomethods differ, but the methods provide approximately thesame rankings of coatings for abrasion resistance.1These test methods
12、 are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directresponsibility of Subcommittee D01.23 on Physical Properties of Applied PaintFilms.Current edition approved June 1, 2015. Published June 2015. Originallyapproved in 1948. Las
13、t previous edition approved in 2010 as D968 05 (2010).DOI: 10.1520/D0968-15.2For 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 onth
14、e ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from Federation of European Producers of Abrasives (FEPA), 20, av.Reille, Paris, F-75014, www.fepa-abrasives.org.Copyright ASTM International, 100
15、Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.3 Each of the methods has been found useful for rating theabrasion resistance of specific types of coatings. For exampleMethod A (falling sand) has been used for rating floor coatingswhile Method B (falling silicon car
16、bide) has been used forrating coatings for ship decks.METHOD AFALLING SAND ABRASION TEST56. Apparatus and Materials6.1 Abrasion Tester, as illustrated in Fig. 1 and Fig. 2.Agatefor starting the flow of abrasive is located near the top of theguide tube. It consists of a metal disk inserted into a sli
17、t in theside of the guide tube with a collar covering the slit. The guidetube shall be firmly supported in a vertical position over asuitable receptacle, which shall contain a support for holdingthe coated panel at an angle of 45 to the vertical. The openingof the tube is directly above the area to
18、be abraded and thedistance from the tube to the coated surface face at the nearestpoint is 25 mm (1 in.) when measured in the vertical direction.The base of the apparatus shall be fitted with adjusting screwsfor properly aligning the equipment.6.2 Standard AbrasiveNatural silica sand from the St.Pet
19、ers or Jordan sandstone deposits (located in the centralUnited States) shall be considered standard when graded asfollows after 5 min of continuous sieving.0 % retained on a No. 16 (1.18 mm) sieveMaximum 15 % retained on a No. 20 (850 m) sieveMinimum 80 % retained on a No. 30 (600 m) sieveMaximum 5
20、% passing a No. 30 (600 m) sieveThe sand is characterized by its roundness of grains and hasa silicon dioxide content greater than 99 %. Use the sievesdescribed in Specification E11.NOTE 1The abrading qualities of sand obtained from different sourcesmay differ slightly even though the sand meets the
21、 sieve requirements.Therefore, for maximum precision of test results, purchaser and sellershould use sand from the same source.7. Test Specimens7.1 Apply uniform coatings of the material to be tested to aplane, rigid surface such as a metal or glass panel. Prepare aminimum of two coated panels for t
22、he material.7.2 Cure the coated panels under the conditions of humidityand temperature agreed upon between the purchaser and seller.NOTE 2The coatings should be applied in accordance with PracticesD823, or as agreed upon between the purchaser and the seller.NOTE 3The thickness of the dry coatings sh
23、ould be measured inaccordance with Test Methods D1005 or D7091.NOTE 4While the minimum of two coated panels is acceptable,evaluating three or more panels per material will provide greater confi-dence in your test results.8. Standardization8.1 Pour a quantity of standard sand into the funnel andexami
24、ne the sand stream falling from the lower end of theguide tube. Align the apparatus by means of the adjustingscrews in the base until the inner concentrated core of the sandstream falls in the center of the flow when viewed at twopositions at 90 to each other. Introduce a measured volume of5Hipkins,
25、 C. C., and Phain, R. J., “The Falling Sand Abrasion Tester,” ASTMBulletin, No. 143, December 1946, pp. 1822.FIG. 1 Apparatus for Falling Sand Abrasion TestNOTE 1All dimensions are given in inches. 1 in. = 25.4 mm.FIG. 2 Design Details of Abrasion Test ApparatusD968 152sand (2000 6 10 mL is a conven
26、ient amount) and determinethe time of efflux. The rate of flow shall be 2 L of sand in 21to 23.5 s.8.2 Secure a trial panel in the testing position, as describedin 6.1, and introduce the sand in increments until a spot 4 mm(532 in.) in diameter is worn through to the base material. Theoverall abrade
27、d area shall be elliptical in shape, about 25 mm(1 in.) in width and 30 mm (114 in.) in length. The center of thearea of maximum abrasion shall be on the centerline throughthe longer axis of the abraded pattern and within 14 to 17 mm(916 to1116 in.) of the top edge. Slight final adjustment of theins
28、trument may be required to center the abrasion spot in thepattern.8.3 A final check on alignment is made by determining theamount of sand that passes through a 4-mm (532-in.) hole in ametal panel placed directly under the tube. Place a containerunder the hole in the panel and allow a weighed amount
29、of sandto pass through the tube onto the panel. Weigh the amount ofsand that passed through the hole into the container. Theapparatus can be considered to be in calibration if the amountof sand that passed through the hole is 90 to 93 % of theamount of sand that impinged on the panel.9. Conditioning
30、9.1 Unless otherwise agreed upon between purchaser andseller, condition the coated test panels for at least 24 h at 23 62C and 50 6 5 % relative humidity. Conduct the test in thesame environment or immediately on removal therefrom.10. Procedure10.1 On each coated panel mark three circular areas, eac
31、happroximately 25 mm (1 in.) in diameter, and so arranged thateach can be properly positioned in the panel support of theabrasion tester. Measure the thickness of the coating by TestMethods D1005 or D7091 in at least three locations in eacharea. Record the mean of each set of measurements as thethic
32、kness of the coating over the respective area.10.2 After conditioning, secure the coated panel in the testeras described in 6.1. Adjust the panel so that one of the markedareas will be centered under the guide tube.10.3 Pour standard sand, measured volumetrically, into thefunnel. Withdraw the gate a
33、nd allow the sand to flow throughthe guide tube and impinge on the coated panel. Collect thesand in a container located at the bottom of the tester. Repeatthis operation until a 4-mm (532-in.) diameter area of thecoating has worn through to the substrate. A convenientincrement of sand to employ duri
34、ng the test is 2000 6 10 mL.As the end-point is approached, increments of 200 6 2mLmay be introduced into the funnel.NOTE 5When the gate is withdrawn from the guide tube, make certainthat a collar covers the slit opening in the tube.10.4 Abrade each of the remaining marked-off areas of thecoated pan
35、el as outlined in 10.2.NOTE 6Check the alignment of the guide tube at frequent intervals toensure that the concentrated inner core of the sand stream is falling in thecenter of the flow.NOTE 7After 25 passes through the apparatus, resieve the sand witha No. 30 sieve to remove fines. Replace the sand
36、 after 50 passes.10.5 Repeat 10.1 10.4 on at least one additional panelcoated with the material under test.11. Calculation11.1 For each area of the coated panel tested, calculate theabrasion resistance, A, in litres per mil from the followingequation:Avolume5 V/T (1)where:V = volume of abrasive used
37、, L (to one decimal place) andT = thickness of coating, mils (to one decimal place).11.2 Calculate the mean of the abrasion resistance valuesobtained for different areas of the coated panel and the meanvalue of the replicate panels.12. Report12.1 Report the following information for each coated pane
38、ltested:12.1.1 Temperature and humidity during curing and at thetime of testing,12.1.2 Type and source of abrasive,12.1.3 Litres of abrasive used for each area tested,12.1.4 Coating thickness in mils for each area tested,12.1.5 Abrasion resistance values for each area tested,12.1.6 Mean abrasion res
39、istance for each coated paneltested, and12.1.7 Mean abrasion resistance and range of the replicatecoated panels.13. Precision613.1 On the basis of an interlaboratory test of this testmethod in which three laboratories tested four types of coatingsdiffering in their abrasion resistance, the within-la
40、boratorycoefficient of variation was found to be 9 % with 22 df and thebetween-laboratories coefficient of variation 35 % with 7 df.Based on these coefficients, the following criteria should beused for judging the acceptability of results at the 95 %confidence level.13.1.1 RepeatabilityTwo results,
41、each the mean of threeruns, obtained by the same operator should be consideredsuspect if they differ by more than 25 % of their mean value.13.1.2 ReproducibilityTwo results, each the mean of threeruns, obtained by operators in different laboratories should beconsidered suspect if they differ by more
42、 than 118 % of theirmean value.NOTE 8The reproducibility of this test is improved substantially whenrankings of the coatings by magnitude of abrasion resistance are used. Inthe interlaboratory test for evaluating precision, all laboratories ranked thecoatings in the same order.13.2 BiasAt the time o
43、f the study, there was no acceptedreference material suitable for determining bias for this testmethod, therefore no statement on bias is being made.6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D01-1037. ContactASTM CustomerS
44、ervice at serviceastm.org.D968 153METHOD BFALLING SILICON CARBIDE TEST14. Apparatus and Materials14.1 Abrasion Tester, as described in 6.1, with two excep-tions:14.1.1 A metal washer with an opening of 8.5 6 0.1 mm iscentered in the bottom opening of the funnel to restrict the flowof the abrasive.14
45、.1.2 The disk gate installed in a slit at the top of the guidetube may be replaced by a gate in the bottom of the funnel. Thisgate consists of a solid metal disk attached to a long verticalscrew and mounted above the washer.14.2 Standard AbrasiveSilicon carbide grain shall beconsidered standard when
46、 graded as follows after 5 min ofcontinuous sieving:0 % retained on a No. 10 (2.00 mm) sieveMaximum of 20 % retained on a No. 14 (1.40 mm) sieveMinimum of 45 % retained on a No. 16 (1.18 mm) sieveMinimum of 70 % retained on a No. 16 (1.18 mm) and No. 18(1.00 mm) sieve3 % Maximum passes a No. 20 (850
47、 m) sieveThese grading requirements correspond to No. 16 grit inaccordance with ANSI B74.12. These grading requirementsalso correspond to F16 grit in accordance with FEPA Standard42-2:2006.14.2.1 Use the sieves described in Specification E11.15. Test Specimens15.1 Prepare the coated panels as outlin
48、ed in 7.1 and 7.2.16. Standardization16.1 Standardize the abrasion tester by the procedures givenin 8.1 8.3, with the following exceptions:16.1.1 Use silicon carbide grain where sand is specified.16.1.2 Weigh the volume of silicon carbide grain to beintroduced into the tester. Determine the efflux t
49、ime for thisvolume. The rate of flow shall be 10 61 g/s.17. Conditioning17.1 Unless otherwise agreed upon between purchaser andseller, condition the coated panels for at least 24 h at 23 6 2Cand 50 6 5 % relative humidity. Conduct the test in the sameenvironment or immediately on removal therefrom.18. Procedure18.1 Measure the thickness of the coating by the proceduresgiven in 10.1.18.2 Abrade the coated panel by the procedures given in10.1 10.4 using silicon carbide as the abrasive. Determine thevolume or weight, or both, of abrasive
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