1、Designation: D 7027 051Standard Test Method forEvaluation of Scratch Resistance of Polymeric Coatings andPlastics Using an Instrumented Scratch Machine1This standard is issued under the fixed designation D 7027; the number immediately following the designation indicates the year oforiginal adoption
2、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.1NOTEFootnote 5 was editorially revised in April 2009.1. Scope1.1 This test method descri
3、bes a laboratory procedure usingan instrumented scratch machine to produce and quantifysurface damage under controlled conditions. This test methodis able to characterize the mar and scratch resistance ofpolymers by measuring many significant material parameters.The scratch-inducing and data acquisi
4、tion process is automatedto avoid user-influenced effects that may affect the results.1.2 The values stated in SI units are to be regarded asstandard.1.3 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
5、standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1FLTM BN 108-13, ISO 1518 and ISO 12137-2 are related tothis test method; the contents are significantly different from this method.2. Referenced Documents2.1 A
6、STM Standards:2D 618 Practice for Conditioning Plastics for TestingD 638 Test Method for Tensile Properties of PlasticsD 1894 Test Method for Static and Kinetic Coefficients ofFriction of Plastic Film and SheetingE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsF 2215 Specif
7、ication for Balls, Bearings, Ferrous and Non-ferrous for Use in Bearings, Valves, and Bearing Applica-tionsG99 Test Method for Wear Testing with a Pin-on-DiskApparatusG 171 Test Method for Scratch Hardness of Materials Usinga Diamond Stylus2.2 ISO Standards:3ISO 1518 Methods of Test for PaintsPart E
8、2: Scratch TestISO 12137-2 Methods of Test for PaintsPart E18: Deter-mination of Mar Resistance using a Pointed StylusISO 3290 Rolling Bearings: BallsDimensions and Toler-ances2.3 Other Standards:FLTM BN 108-13 Resistance to Scratching43. Terminology3.1 Definitions:3.1.1 critical normal load, nthe n
9、ormal load at whichwhitening (see 3.1.10) of the material within the scratch groovefirst occurs.3.1.2 friction force, nthe tangential force present at theinterface between two bodies when one body moves or tends tomove relative to the other, under the action of an external force.Depending on the pen
10、etration of the indenter into the testsurface, friction force can be caused by sliding (relatively smalldisplacement of material) or ploughing (gross removal/displacement of materials).3.1.3 mar resistance, nability to resist surface damagefrom the light abrasion by small objects. Quantitatively, it
11、 canbe characterized by the loss in gloss, increase in haze, or slightshift in gray level.3.1.4 normal load, na load acted onto the scratch stylusthat is imposed in a vertically downward direction whilemaintaining its perpendicularity with the direction of scratch.3.1.5 scratch depth, nthe vertical
12、distance to be measuredfrom the trough of the scratch groove to (a) its peak or (b) tothe undisturbed specimen surface.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approve
13、d June 1, 2005. Published June 2005.2For 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 onthe ASTM website.3Available from American
14、National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from Ford Motor Company, Central Laboratories, 15000 CenturyDrive, Dearborn, MI 48120.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
15、United States.3.1.6 scratch resistance, nability to withstand damagethat is accompanied by the gross deformation typically asso-ciated with sharp objects that may involve compressing,ploughing, and shearing off of material. Quantification can beaccomplished through the measurement of scratch depth(3
16、.1.5), scratch width (3.1.7) and other geometric characteris-tics of the scratch.3.1.7 scratch width, nthe horizontal distance between thetwo peaks on both sides of the scratch groove.3.1.8 scratching, vmechanical removal, or displacement,or both of material from a surface by the action of abrasivep
17、articles, or protuberances, or both sliding across the surfaces.3.1.9 scratching coeffcient of friction, nthe ratio of thefriction force (3.1.2) to the normal load (3.1.4). This coefficientis a measure of the resistance of a material to scratching. Fortests conducted under constant load, two distinc
18、t quantitiesmay be characterized, the static and kinetic coefficients. Thestatic coefficient is related to the friction force measured priorto the movement of the scratch stylus while the kineticcoefficient is related to the constant friction force measured insustaining this movement. This quantity
19、is not equivalent to thecoefficient of friction, which is obtained in accordance withTest Method D 1894 and is similar to the stylus drag coefficientas defined in Test Method G 171.3.1.10 whitening, nthe visible damage along the scratchgroove of the surface caused by microcracking, voiding,crazing,
20、and debonding.4. Summary of Test Method4.1 This test method utilizes an automated scratch machineto administer controlled scratch tests on polymeric specimens.Two basic test modes (Test Modes A and B) are presented.4.1.1 Test Mode AA scratch is applied onto the specimensurface under an increasing lo
21、ad from 2 to 50 N 6 0.1 N overa distance of 0.1 m 6 0.0005 m at a constant rate of 0.1 m/s 60.0005 m/s - average. This test mode is intended to determinethe critical normal load at which whitening will occur for amaterial system. For materials that do not show any whitening,the normal load at which
22、a predetermined scratch width existswill be used as a basis for comparison. To compare and rankdifferent materials, the normal load shall be plotted as afunction of the scratch width.4.1.2 Test Mode BA scratch is applied onto the specimensurface under a constant load of 30 N 6 0.1 N over a distanceo
23、f 0.1 m 6 0.0005 m at a constant rate of 0.1 m/s 6 0.0005 m/s- average. This test mode is intended to evaluate the homoge-neous response of the material and establish the scratchingcoefficient of friction.4.2 Scratched surface can be visually inspected or by usingevaluation tools to study the surfac
24、e damage. For Test ModeA,the critical normal load is determined by the onset of thewhitening of the material due to scratch. Measurement of thescratch widths, or depths, or both shall also be taken to aid thequantification of scratch resistance.4.3 Scratching coefficient of friction as defined in 3.
25、1.9 canbe computed for material characterization using the frictionforce 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 particularmaterial,(2) to rank the relative scratch resistance of
26、 differentmaterials, or(3) to determine the scratching coefficient of friction ofmaterials.5.2 Since polymers exhibit mechanical properties that arestrongly dependent on temperature, the test method prescribedherein is designed to yield reproducible results when usersperform tests under the similar
27、testing environment and onspecimens of the same material and surface texture that aresubjected to the same conditioning procedures.5.3 Certain polymers are self-healing (recoverable) whensubjected to scratches and other physical deformations becauseof their viscoelastic and relaxation properties. It
28、 is important tonote the difference between the instantaneous (if readilymeasurable) and the post-scratch damages and appropriatelycompare results to ensure reproducibility.5.4 “Whitening” of the scratched surface is a key damagemechanism that has prompted much concern in automotive andother applica
29、tions where surface aestheticism is important.This type of damage is undesirable because it is evident tohuman eyes. The critical normal load at which this phenom-enon appears serves as a benchmark in ranking materialperformance.5.5 For polymers that do not exhibit whitening, a scratchgroove from se
30、vere ploughing is still highly noticeable. In suchcases, the normal load required to achieve a certain scratchwidth shall be reported to characterize scratch visibility andscratch resistance. The critical scratch width shall be decidedby users in accordance with the specific material and remainsthe
31、same throughout a set of tests for a consistent comparison.The variation of the scratch width as a function of the appliedload shall also be plotted for comparison purposes.6. Apparatus6.1 General DescriptionThe instrumented scratch ma-chine5described here has been developed at Texas A a schematic o
32、f the scratch machine is shown in Fig. 1.The instrument consists of a sample stage, clamping devices, aspring-load/dead-load system, and a horizontal motion servosystem. Optional systems such as load and position sensingsystem, data acquisition and computer systems can be includedwhen position and l
33、oad data are required. An environmentalchamber can also be added for non room-temperature (23 62C) tests. For post-scratch study, evaluation instruments likeoptical microscopes, flatbed scanners and image capturingtools can separately be used.6.2 Spring-Load MechanismThe instrument is a stylus-type
34、scratcher in which a 1-mm-diameter spherical tip is used5The sole source of supply of the apparatus known to the committee at this timeis Surface Machine Systems, LLC, http:/. If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments
35、 will receive careful consideration at a meetingof the responsible technical committee1, which you may attend.D70270512to scratch the surface of a flat specimen. It consists of a samplestage with dimensions of 305 by 305 mm2on which testspecimens can be anchored. The spring-load driven mecha-nism, c
36、apable of generating 0 to 75 N of normal load, exerts theforce onto the scratch stylus, either at a constant magnitude orincreasingly to a desired magnitude.6.3 Dead-Load MechanismThe dead-load mechanism, aspresented in Fig. 1, is similar to the setup of the spring-loadmechanism as in 6.2, except th
37、at it uses dead weights for thenormal load during scratch. This setup can also be used for TestMode B, where a constant load is required.6.4 Horizontal Motion Servo SystemAhigh-precision mo-tor controlled via microprocessor, actuates the scratch stylus.The horizontal speed of the scratch stylus can
38、be set at aconstant rate between 0 to 400 mm/s or with a constantacceleration from 0 to 400 mm/s2.6.5 Load and Position Sensing System (optional)If re-quired, the instrument can be incorporated with devices tomonitor the normal load, friction force, instantaneous scratchdepth and horizontal position
39、. The friction force acting on thestylus shall be measured with an accuracy of 0.1 N. The dataacquired for depth, horizontal position and velocity of thestylus shall have accuracy of 0.5 m, 5 m and 0.0005 m/s(average), respectively.6.6 Data Acquisition and Computer Systems (optional)Connections from
40、 the sensing system to the computer systemmust be insulated against electromagnetic interference toensure clean and reliable data. The computer system shall havethe capability to collect the force and position data. Theminimum sampling rate for the data acquisition system shall bekept at 1000 data p
41、oints per second for reliable and accuratedata.6.7 Environmental Chamber (optional)An environmentalchamber with heating and cooling controls allows experimentsto be performed from 50 to 100C.6.8 Evaluation InstrumentsOther than visual inspection,the scratch grooves can be further examined with optic
42、almicroscopes, flatbed scanners, or interferometers, or a combi-nation of the three, for measuring scratch widths and depths.Since the capability and sensitivity of each device are different,it is required that the adopted method of evaluation be reported.For the purpose of quantifying whitening, ot
43、her instrumentsthat are capable of measuring reflected light intensity in thescratch groove can be used. The basic requirement for anyinstrument is that light conditions shall be controlled to havethe sensitivity to detect the whitening point within 0.05 mm.6.9 Stylus TipThe setup of the scratch mac
44、hine providesthe added flexibility of allowing the interchangeability of stylustip in their material and geometry. The material of the scratchstylus tip shall be stainless steel and its shape shall be sphericalwith a diameter of 1 mm. Surface quality of the tip shall be ofGrade 10 or better, in acco
45、rdance with Specification F 2215 orISO 3290.NOTE 2Other materials for the stylus tip are acceptable so long asthey have higher indentation hardness than the test material. If the relativehardness of the materials is significantly different from the stainless steel,the resulting scratch test data wil
46、l be dissimilar as those yielded by astainless steel spherical tip. Using a tip of other geometry is optional buttheir results shall not supersede those from the spherical tip tests.7. Hazards7.1 The scratch carriage could suddenly accelerate to 400mm/s; precaution shall be taken to avoid having han
47、ds, fingers,and loose clothing pinched by the moving part.7.2 When performing tests at extreme temperatures, ensurethat thermally insulated gloves are used in handling specimens.8. Test Specimens and Sample Preparation8.1 MaterialsThe test method can be applied to a varietyof polymeric and coating m
48、aterials. The materials must be ableto be prepared to the desired dimensions and able to withstandthe stresses imposed during the test without failure or excessivefracture. The materials being tested shall be described bydimensions, surface finish, material type, form, composition,processing treatme
49、nt and, when appropriate, indentation hard-ness (see Test Method G99).8.2 Tensile SpecimensInjection-molded tensile bars asspecified in Test Method D 638 (Test specimen I-III) areFIG. 1 Schematic of the Instrumented Scratch MachineD70270513acceptable for use with this test. Typical thickness shall bebetween 3 and 10 mm. Since the scratch length for differenttest modes is taken to be 100 mm, the specimen shall be at least140 mm in length to provide enough area for clamping at bothends. Experiments have shown that thickness
