1、Designation: D7027 051D7027 13Standard Test Method forEvaluation of Scratch Resistance of Polymeric Coatings andPlastics Using an Instrumented Scratch Machine1This standard is issued under the fixed designation D7027; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEFootnote 5 was editorially revised in April 2009.1. Scope1.1 This test method
3、 describes a laboratory procedure using an instrumented scratch machine to produce and quantify surfacedamage under controlled conditions. This test method is able to characterize the mar and scratch resistance of polymers bymeasuring many significant material parameters. The scratch-inducing and da
4、ta acquisition process is automated to avoiduser-influenced effects that may affect the results.1.2 The values stated in SI units are to be regarded as standard. The values in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, assoc
5、iated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1FLTM BN 108-13, ISO 1518 and ISO 12137-2 are related to this test method; the contents are signifi
6、cantly different from this method.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD1894 Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and SheetingE177 Practice for Use of th
7、e Terms Precision and Bias in ASTM Test MethodsF2215 Specification for Balls, Bearings, Ferrous and Nonferrous for Use in Bearings, Valves, and Bearing ApplicationsG99 Test Method for Wear Testing with a Pin-on-Disk ApparatusG171 Test Method for Scratch Hardness of Materials Using a Diamond Stylus2.
8、2 ISO Standards:3ISO 1518 Methods of Test for PaintsPart E2: Scratch TestISO 12137-2 Methods of Test for PaintsPart E18: Determination of Mar Resistance using a Pointed StylusISO 3290 Rolling Bearings: BallsDimensions and Tolerances2.3 Other Standards:FLTM BN 108-13 Resistance to Scratching43. Termi
9、nology3.1 Definitions:3.1.1 ASV Software, nAutomatic Scratch Visualization, a computer program which automates the identification of the pointof failure in a rising load scratch tests using contrast as the failure criteria. The software determines failure if a continuous changein contrast between th
10、e scratch groove and the undamaged material surface reaches +3 %, -3 %, or 63 %. The continuity criterionis defined as a region of length equal to 2 diameters of the scratch stylus with 90 % or more of the region exceeding the contrastcriterion.The lowest load point on the scratch from which there i
11、s a continuous contrasting region is considered the point of failure.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved June 1, 2005Oct. 15, 2013. Published June 2005
12、October 2013. Originally approved in 2005. Last previous edition approved in 2005 asD7027051. DOI: 10.1520/D7027-05E01.10.1520/D7027-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume inf
13、ormation, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately
14、depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
15、 19428-2959. United States1This program is useful for visual analysis of the test and may be used for other applications, such as pass-fail criterion for scratchvisibility. An example of the application of ASV is shown in Fig. 1.3.1.2 critical normal load, nthe normal load at which whiteningfailure
16、(see 3.1.103.1.4) of the material within the scratchgroove first occurs.3.1.3 normal load, na load applied onto the scratch stylus that is imposed in a vertically downward direction, perpendicularto the surface of the specimen. The normal load is also referred to as the “Z-direction load.”3.1.4 fric
17、tion force, point of failure, nthe tangential force present at the interface between two bodies when one body movesor tends to move relative to thepoint along a rising-load scratch path at which the damage to the surface is first considered to beunacceptable. The point of failure for a given study s
18、hall be defined in a quantifiable manner. For aesthetic studies therecommended criteria is a contrast of 63 % between the scratch groove and the undamaged material surface. For different studiesother criteria for failure may be used. For example, failure may occur when the scratch width or depth exc
19、eeds a predeterminedvalue. Onset of micro-cracking, crazing, fish-scale formation, plowing can also be used as failure criteria. For a coated specimenthe point of failure might be defined as the point at which the coating is penetrated, revealing the underlying substrate. An imageof styrene acryloni
20、trile (SAN) subjected toTest ModeA(4.1.1 other, under the action of an external force. Depending on the) undera linearly increasing normal load range of 1-90 N is shown in Fig. 1 penetration of the indenter into the test surface, friction forcecan be caused by sliding (relatively small displacement
21、of material) or ploughing (gross removal/displacement of materials).toillustrate several possible points of failure that can occur during the scratch process.3.1.3 mar resistance, nability to resist surface damage from the light abrasion by small objects. Quantitatively, it can becharacterized by th
22、e loss in gloss, increase in haze, or slight shift in gray level.3.1.5 normal load, scratch coeffcient of friction, nthe ratio of the tangential force (3.1.10) to the normal load (3.1.3a loadacted onto the scratch stylus that is imposed in a vertically downward direction while maintaining its perpen
23、dicularity ). Thiscoefficient is a measure of the resistance of a material to scratching motion. For tests conducted under constant load, two distinctquantities may be characterized, the static and kinetic coefficients. The static coefficient is related to the tangential force measuredprior to the m
24、ovement of the scratch stylus while the kinetic coefficient is related to the constant tangential force measured insustaining this movement. This quantity is not equivalent to the coeffcient of friction,with which is obtained in accordance withTest Method D1894 and is similar to the direction of scr
25、atch.stylus drag coeffcient as defined in Test Method G171.3.1.6 scratch depth, nthe vertical distance to be measured from the trough of the scratch groove to (a) its peak or (b) to theundisturbed specimen surface.the undisturbed specimen surface (D1) or to the peaks of the scratch path (D2). Refer
26、to Fig. 2.3.1.7 scratch resistance, nability to withstand damage that is accompanied by the gross deformation typically associated withsharp objects sliding indentation of asperities that may involve compressing, ploughing,plowing, and shearing off of material.Quantification can be accomplished thro
27、ugh the measurement of critical normal load scratch depth (3.1.53.1.6), scratch width(3.1.73.1.8) and other geometric or visual characteristics of the scratch.3.1.8 scratch width, nthe horizontal distance between the two peaks on both sides of the scratch groove.groove (W1). Referto Fig. 2.3.1.9 scr
28、atching, vprocess involving surface deformation (displacement or mechanical removal, or displacement, or both ofmaterial from a surface both, of material) caused by the action of abrasive particles, one of more asperities, or protuberances, orboth, sliding across the surfaces.surface.FIG. 1 Schemati
29、c of the Instrumented Scratch MachineImages of Polystyrene-Acrylonitrile (SAN) Subjected to Test Mode A Under aProgressive Load of 1-90 N Showing Examples of Points of FailureD7027 1323.1.10 scratching coeffcient of friction, tangential force, nthe ratio of the friction force (force present at the i
30、nterface betweenthe3.1.2) to the normal load ( scratch tip and the specimen, acting opposite to the direction 3.1.4). This coefficient is a measureof the resistance of a material to scratching. For tests conducted under constant load, two distinct quantities may be characterized,the static and kinet
31、ic coefficients.The static coefficient is related to the friction force measured prior to the movement of the scratchstylus while the kinetic coefficient is related to the constant friction force measured in sustaining this movement. This quantity isnot equivalent to the coefficient of friction, whi
32、ch is obtained in accordance with Test Method of motion of the scratch tip. Thetangential force acts parallel to the scratch direction and is composed of two components: the kinetic friction acting on the scratchtip, plus the reaction force generated during deformation of the surface. The magnitude
33、of the component forces can vary.At smallscratch depths the tangential force is kinetic friction. As scratch depth increases, the forces due to elastic and plastic deformationincrease. Tangential forceD1894 and is similar to the stylus drag coefficient as defined in Test Methodalso referred to as th
34、e“X-direction force” measured G171.by the scratch instrument.3.1.11 whitening, nthe visible damage along the scratch groove of the surface caused by microcracking, voiding, crazing, anddebonding.a phenomenon occurring as a result of light scattering by surface deformation resulting from the scratch
35、process thatcauses the scratch path to be brighter, or “whiter,” than the undisturbed background surface. Key deformation mechanisms includeincrease in surface roughness due to micro-cracking. Whitening is measurable as a contrast change between the scratch groove andthe undamaged material surface.4
36、. Summary of Test Method4.1 This test method utilizes an automated scratch machine to administer controlled scratch tests on polymeric specimens. Twobasic test modes (Test Modes A and B) are presented.4.1.1 Test Mode AA scratch is applied onto the specimen surface under an increasing normal load fro
37、m 2 to 50 N 6 0.1 N(60.5 N) over a distance of 0.1 m60.0005 m (60.0001 m) at a constant scratch rate of 0.1 m/s60.0005 m/s - average. (60.0005m/s). This test mode is intended to determine the critical normal load at which whitening will occur for for failure for a materialsystem. The point of failur
38、e should occur in the second or third quartile of the test length. For materials that do not show anywhitening, the normal load at which a predetermined scratch width exists will be used as a basis for comparison. To compare andrank different materials, the normal load shall be plotted as a function
39、 of the scratch width.exhibit failure in this range, the loadrange may be changed to ensure that the point of failure occurs in the middle of the scratch path.4.1.2 Test Mode BA scratch is applied onto the specimen surface under a constant normal load of 30 N 6 0.1 N (60.1 N)over a distance of 0.1 m
40、 6 0.0005 m (60.0001 m) at a constant scratch rate of 0.1 m/s 6 0.0005 m/s - average. (60.0005 m/s).This test mode is intended to evaluate the load-dependant homogeneous response of the material and establish the scratching-scratch coefficient of friction. The constant load value may be increased if
41、 30 N is insufficient to generate damage on the specimen.4.2 Scratched The scratched surface can be visually inspected visually or by using evaluation tools to study the surface damage.For Test ModeA, the critical normal load is determined by the onset of the whitening of the material due to scratch
42、. point of failureFIG. 2 Differences in Surface Damage(a) Polycarbonate Does Not Exhibit Whitening (b) Polypropylene Does Show Whitening.CrossSection of Scratch Path Showing Scratch Width Measurement (W1) and Depth Measurements (D1 and D2)D7027 133criteria established for that experiment. Measuremen
43、t of the scratch widths,width, or depths,depth, or both shallboth, may also betaken to aid the quantification of scratch resistance.ASV Software may be used to automate the measurement of the point of failurewith regard to scratch visibility.4.3 ScratchingScratch coefficient of friction as defined i
44、n 3.1.93.1.5 can be computed for material characterization using thefrictiontangential force and normal load data recorded during tests.5. Significance and Use5.1 Scratch tests are performed on specimens:(1) to evaluate the scratch or mar resistance of a particular material,(2) to rank the relative
45、scratch resistance of different materials, or(3) to determine the scratchingscratch coefficient of friction of materials.5.2 Since polymers exhibit mechanical properties that are strongly dependent on temperature, the test methodstandardprescribed herein is designed to yield reproducible results whe
46、n users perform tests under the similar testing environment and onspecimens of the same material and surface texture that are subjected to the same conditioning procedures.5.3 Certain polymers are self-healing (recoverable) when subjected to scratches and other physical deformations because oftheir
47、viscoelastic and relaxation properties. It is important to note the difference between the instantaneous (if readily measurable)and the post-scratch damages and appropriately residual scratch damage and compare results appropriately to ensurereproducibility. It is recommended that 24 hours be allowe
48、d for viscoelastic recovery when considering residual scratch depth.5.4 “Whitening” of the scratched surface is a key damage mechanism that has prompted much concern in automotive and otherapplications where surface aestheticismaesthetics is important. This type of damage is undesirable because it i
49、s evident to thehuman eyes.eye. The critical normal load at which this phenomenon appears serves as a benchmark in ranking materialperformance.performance, especially from an aesthetic point of view.5.5 For polymers that do not exhibit whitening, a scratch groove from severe ploughing is still highly noticeable. In such cases,the normal load required to achieve a certain scratch width shall be reported to characterize scratch visibility and scratch resistance.The critical scratch width shall be decided by users in accordance with the specific material a
