1、Designation: D 6988 07Standard Guide forDetermination of Thickness of Plastic Film Test Specimens1This standard is issued under the fixed designation D 6988; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers the determination of the thickness ofplastic films where the thickness is used directly in determiningthe resul
3、ts of tests for various properties. Use this practiceexcept as otherwise required in material specifications or inapplicable test standards.NOTE 1Films are defined as having thicknesses#0.250 mm #0.010in.NOTE 2Alternative methods are acceptable if they meet the require-ments of measurement precision
4、 as noted in this guide.NOTE 3This guide is not intended to address the sampling techniquesor the measurement of film thickness for the commercial classification ofcommercial products or for quality control purposes.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standar
5、d 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 requirements prior to use.NOTE 4ISO 4593 is similar but
6、differs in technical content and scope.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 4805 Terminology for Plastics Standards3D 5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD 6287 Practice
7、for Cutting Film and Sheeting Test Speci-mens2.2 ISO Standard:ISO 472 PlasticsVocabulary43. Terminology3.1 DefinitionsSee Terminologies D 883 and D 4805, andISO 472 for definitions pertinent to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 absolute uncertainty (of a measurement
8、), nthesmallest division that can be read directly on the instrumentused for measurement.3.2.2 calibration, nthe set of operations that establishes,under specified conditions, the relationship between valuesmeasured or indicated by an instrument or system, and thecorresponding reference standard or
9、known values derivedfrom the appropriate reference standards.3.2.3 dead-weight micrometer, nan instrument capable ofmeasuring the thickness of thin films utilizing a weight to applyuniform pressure to the specimen.3.2.4 verification, nproof, with the use of calibratedstandards or standard reference
10、materials that the calibratedinstrument is operating within specified requirements.4. Summary of Methods4.1 This guide describes four different methods for thethickness measurement of plastic film specimens. The methods(identified as Methods A, B, C, and D) use different microme-ters that actuate th
11、e weights in different manners or utilizedifferent means of reading the thickness.4.2 It is permissible to use other instruments, includingnon-contact instruments and instruments using alternativereadout systems in place of dials provided they meet or exceedthe precision requirements noted in this p
12、ractice.5. Significance and Use5.1 This guide is intended to provide recommendations andsuggested good practices to determine precise dimensionswhen necessary for the calculation of properties expressed inphysical units. It is not intended to replace practical thickness1This guide is under the juris
13、diction of ASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.19 on Film and Sheeting.Current edition approved March 1, 2007. Published March 2007. Originallyapproved in 2003. Last previous edition approved in 2003 as D 6988 - 03.2For referenced ASTM standards, visit
14、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.3Withdrawn.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor,
15、New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.measurements based on commercial portable tools, nor is itimplied that thickness measurements made b
16、y the procedureswill agree exactly.6. Apparatus6.1 The instruments described in this guide share manycommon features:6.1.1 A dead-weight gauge calibrated in accordance withthe guidelines described in Appendix X2 and consisting of thefollowing:NOTE 5Additional guidance for calibration and verificatio
17、n of gaugescan be found in Test Methods D 5947.NOTE 6Since there is such a wide variety of instruments in use, therecan be significant differences in the accuracy of different instrument types.The values stated for each type of apparatus are intended to be typical ofthat type of instrument.6.1.1.1 A
18、presser foot that moves in an axis perpendicular tothe anvil face;6.1.1.2 The surfaces of the presser foot and anvil (whichcontact the specimen) parallel to within 2.5 m;6.1.1.3 A spindle, vertically oriented if a dead-weight appa-ratus;6.1.1.4 An indicator essentially capable of repeatable read-ing
19、s within 6 0.001 mm at zero setting, or on a steel gaugeblock;6.1.1.5 A frame, housing the indicator, of such rigidity thata load of 15 N applied to the housing, out of contact with thepresser foot spindle (or any weight attached thereto), willproduce a deflection of the frame not greater than the s
20、mallestscale division or digital count on the indicator;6.1.1.6 If employed, a dial diameter of at least 50 mm andgraduated continuously to read directly to the nearest 2.5 m.The dial can be equipped with a revolution counter thatdisplays the number of complete revolutions of the large hand,or6.1.1.
21、7 An electronic instrument having a digital readout inplace of the dial indicator if that instrument meets all of theother requirements of this guide, and6.1.1.8 The force applied to the presser foot spindle and theforce necessary to register a change in the indicator readingshall be less than the f
22、orce that will cause deformation of thespecimen. The force applied to the presser foot spindle and theforce necessary to just prevent a change in the indicator readingshall be more than the minimum permissible force specified fora specimen.6.2 Apparatus AManually Operated Thickness Gauge:6.2.1 An in
23、strument having a presser foot and spindle that ismanually lifted and lowered.6.3 Apparatus BAutomatically Operated ThicknessGauge:6.3.1 A pneumatic or motor-operated instrument having apresser foot spindle that is lifted and lowered either by apneumatic cylinder or by a constant-speed motor through
24、 amechanical linkage such that the rate of descent (for a specifiedrange of distances between the presser foot surface and anvil)and dwell time on the specimen are within the limits specifiedfor the material being measured.6.3.2 A preferred drop rate between 0.750 and 1.500 mm/sbetween 0.625 and 0.0
25、25 mm on the dial and a capacity of atleast 0.775 mm.6.4 Apparatus CManually Operated Thickness Gaugewith Linear Optical Encoder:6.4.1 Similar to Apparatus A except it employs a digitaldevice with an electronic readout capable of repeatable read-ings to within 6 1 m at zero setting or on a steel gau
26、ge blockand a linear optical encoder using a scale of increments not lessthan 100 lines/mm and capable of reading within 0.5 m witha 10 mm range.6.5 Apparatus DAutomatically Operated ThicknessGauge with Digital Display:6.5.1 Similar toApparatus B except it employs an electronicdevice with a digital
27、readout capable of a resolution not lessthan 0.5 m and repeatable readings to within 6 1 m at zerosetting or on a steel gauge block.6.5.2 A preferred drop rate between 0.750 and 1.500 mm/sbetween 0.625 and 0.025 mm on the dial and a capacity of atleast 0.775 mm.6.6 Other Instruments:6.6.1 Other inst
28、ruments are commercially available thatutilize different methods of measuring thickness. These aregenerally non-contact devices employing ultrasonic response,electrical capacitance, or similar material properties that can becorrelated to thickness. Some of these devices are also de-signed to provide
29、 a means of measuring discreet sections offilm in a continuous scanning mode. Instruments of this natureare acceptable provided they meet or exceed the precisionrequirements noted in this practice and the requirements of theapplicable material or product specifications or applicable teststandards.7.
30、 Test Specimens7.1 The test specimens shall be prepared from plastic filmsthat have been cut to the required dimensions according toPractice D 6287.7.2 Prepare and condition each specimen in equilibriumwith the appropriate standard laboratory test conditions or inaccordance with the conditions speci
31、fied in the test methodapplicable to the specific material for test.7.3 For each specimen, take precautions to prevent damageor contamination that will adversely affect the measurements.7.4 Unless otherwise specified, make all dimension mea-surements at the standard laboratory atmosphere in accordan
32、cewith Practice D 618.8. Procedure8.1 General Guidelines:NOTE 7In this section, the word “method” denotes a combination ofboth a specific apparatus and a procedure describing its use.8.1.1 The selection of a method for measurement of filmthickness is influenced by the characteristics of the film for
33、measurement. Each material and, in some cases, film construc-tion in the case of multi-layer structures, will differ in itsresponse to test method parameters, which include, but are notlimited to, compressibility, rate of loading, ultimate load, dwelltime, and dimensions of the presser foot and anvi
34、l. For aD6988072specific plastic material or structure, these responses can, insome cases, cause measurements made using one method todiffer significantly from measurements made using anothermethod. The procedures that follow are categorized accordingto the materials to which each applies. See Appen
35、dix X1.NOTE 8The pressure exerted by the gauge on the specimen beingmeasured shall not distort or deform the specimen. For thin films,#0.025mm 0.001 in., or films which exhibit visual deformation duringmeasurement, a maximum pressure of 70 kPa 10 psi is suggested. Forthicker or stiffer films, a pres
36、sure range between 160 and 185 kPa 23 and27 psi is suggested. See Table 1.NOTE 9An electronic gauge can be substituted for the dial gauge inMethod A or B if the presser foot and anvil meet the requirements of thatmethod.8.1.2 The presence of contaminating substances on thesurfaces of the test specim
37、ens, presser foot, anvil, or spindlecan interfere with dimension measurements and result inerroneous readings. To help prevent this interference, selectonly clean specimens for testing, and keep them and thedimension measuring instrument covered until ready to makemeasurements. (WarningCleaning the
38、presser foot and anvilsurfaces as described in X2.1 can cause damage to digitalelectronic gauges resulting in very expensive repairs by theinstrument manufacturer. Obtain procedures for cleaning suchelectronic gauges from the instrument manufacturer to preventthese costs.)8.1.3 One thickness determi
39、nation per specimen or theaverage thickness determined by a continuous scanning instru-ment is acceptable if it can be demonstrated that the overallthickness does not deviate 6 10 % from the average. This isespecially applicable if measurements are being made forreference, that is, to report nominal
40、 film thickness, and are notrequired for the determination of specific properties.8.1.4 Some instruments do not require calibration. For theseinstruments, periodic verification procedures should be con-ducted according to the recommendations of the instrumentsupplier.8.2 Method A:8.2.1 Using Apparat
41、us A and specimens in conformancewith Section 7, place the instrument on a solid, level, cleantable or bench that is free of excessive vibration. Confirm thatthe anvil and presser foot surfaces are clean. Adjust the zeropoint.8.2.2 Lower the presser foot on an area of the specimen formeasurement. Ob
42、serve this reading.8.2.3 Raise the presser foot slightly.8.2.4 Move the specimen to the first measurement location,and lower the presser foot to a reading approximately 0.007 to0.010 mm higher than the initial reading of 8.2.2.8.2.5 Drop the foot onto the specimen (see Warning in8.1.2).NOTE 10This p
43、rocedure minimizes small errors present when thepressure foot is lowered slowly onto the specimen and does not allow thepresser foot to seat properly.8.2.6 Observe the reading. After correcting the observedindicated dimension, record the corrected dimension value. Amethod for developing a calibratio
44、n correction curve is de-scribed in X2.4.8.2.7 Move the specimen to another measurement position,and repeat the steps given in 8.2.3 through 8.2.6.8.2.8 Unless otherwise specified, make and record at leastthree dimension measurements on each specimen. The arith-metic mean of all dimension values is
45、the dimension of thespecimen.8.2.9 Recheck the instrument zero setting after measuringeach specimen. If a change is observed, this is usuallyindicative of contamination on the contact surfaces and willrequire cleaning. (See Warning in 8.1.2 and Note 9.)8.3 Method B:8.3.1 Using Apparatus B and specim
46、ens in conformancewith Section 7, place the instrument on a solid, level, cleantable or bench that is free of excessive vibration. Confirm thatthe anvil and presser foot surfaces are clean.8.3.2 Apply power to the motor or air to the pneumatics, andallow the instrument to reach a thermal equilibrium
47、 with theambient. Equilibrium is attained when the zero point adjust-ment becomes negligible. Do not stop the motor or remove theair until all of the measurements are made. This will minimizeany tendency to disturb the thermal equilibrium between theinstrument and ambient during the dimension measur
48、ements.8.3.3 Insert and position a specimen for the first measure-ment when the opening between the presser foot and anvil isnear its maximum.8.3.4 Observe the dial reading while the presser foot is atrest on the specimen surface. After correcting the observedindicated dimension, record the correcte
49、d dimension value. Amethod for developing a calibration correction curve is de-scribed in X2.4.8.3.5 While the presser foot is near its maximum lift, movethe specimen to another measurement position, and repeat thesteps given in 8.3.3 and 8.3.4.8.3.6 Unless otherwise specified, make and record at leastthree thickness measurements on each specimen. The arith-metic mean of all dimension values is the thickness of thespecimen.8.3.7 Recheck the instrument zero setting after measuringeach specimen. If a change is observed, this is usuallyindicative of cont
