1、Designation: D6988 08D6988 13Standard Guide forDetermination of Thickness of Plastic Film Test Specimens1This standard is issued under the fixed designation D6988; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers the determination of the thickness of plastic films where the thickness is used directly in determining th
3、eresults of tests for various properties. Use this practice except as otherwise required in material specifications or in applicable teststandards.NOTE 1Films are defined Film is defined in Terminology D883 as having thicknesses 0.250 mm 0.010 in.an optional term for sheeting havinga nominal thickne
4、ss no greater than 0.25 mm (0.010 in).NOTE 2Alternative methods are acceptable if they meet the requirements of measurement precision as noted in this guide.NOTE 3This guide is not intended to address the sampling techniques or the measurement of film thickness for the commercial classification ofco
5、mmercial products or for quality control purposes.1.2 The values stated in SI units are to be regarded as the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropri
6、ate safety and health practices and determine the applicability of regulatoryrequirements prior to use.NOTE 4This standard and ISO 4593 address the same subject matter but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 T
7、erminology Relating to PlasticsD4805 Terminology for Plastics Standards (Withdrawn 2002)3D5947 Test Methods for Physical Dimensions of Solid Plastics SpecimensD6287 Practice for Cutting Film and Sheeting Test Specimens2.2 ISO Standard:ISO 472 PlasticsVocabulary33. Terminology3.1 DefinitionsSee Termi
8、nologies D883 and D4805, and ISO 472 for definitions pertinent to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 absolute uncertainty (of a measurement), nthe smallest division that can be read directly on the instrument used formeasurement.3.2.2 calibration, nthe set of operati
9、ons that establishes, under specified conditions, the relationship between values measuredor indicated by an instrument or system, and the corresponding reference standard or known values derived from the appropriatereference standards.3.2.3 dead-weight micrometer, nan instrument capable of measurin
10、g the thickness of thin films utilizing a weight to applyuniform pressure to the specimen.1 This guide is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.19 on Film, Sheeting, and MoldedProducts.Current edition approved Nov. 1, 2008April
11、1, 2013. Published November 2008April 2013. Originally approved in 2003. Last previous edition approved in 20072008 asD6988 - 07.D6988 - 08. DOI: 10.1520/D6988-08.10.1520/D6988-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org.
12、 For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.This document is not an ASTM standard and is intended only to provide th
13、e 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 depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standa
14、rd as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.4 verification, nproof, with the use of calibrated
15、standards or standard reference materials that the calibrated instrumentis operating within specified requirements.4. Summary of Methods4.1 This guide describes four different methods for the thickness measurement of plastic film specimens. The methods(identified as Methods A, B, C, and D) use diffe
16、rent micrometers that actuate the weights in different manners or utilize differentmeans of reading the thickness.4.2 It is permissible to use other instruments, including non-contact instruments and instruments using alternative readoutsystems in place of dials provided they meet or exceed the prec
17、ision requirements noted in this practice.5. Significance and Use5.1 This guide is intended to provide recommendations and suggested good practices to determine precise dimensions whennecessary for the calculation of properties expressed in physical units. It is not intended to replace practical thi
18、cknessmeasurements based on commercial portable tools, nor is it implied that thickness measurements made by the procedures will agreeexactly.6. Apparatus6.1 The instruments described in this guide share many common features:6.1.1 A dead-weight gauge calibrated in accordance with the guidelines desc
19、ribed in Appendix X2 and consisting of thefollowing:NOTE 5Additional guidance for calibration and verification of gauges can be found in Test Method D5947.NOTE 6Since there is such a wide variety of instruments in use, there can be significant differences in the accuracy of different instrument type
20、s. Thevalues stated for each type of apparatus are intended to be typical of that type of instrument.6.1.1.1 A presser foot that moves in an axis perpendicular to the anvil face;6.1.1.2 The surfaces of the presser foot and anvil (which contact the specimen) parallel to within 2.5 m;6.1.1.3 A spindle
21、, vertically oriented if a dead-weight apparatus;6.1.1.4 An indicator essentially capable of repeatable readings within 6 0.001 mm at zero setting or within 60.001 mm whenusing a steel gauge block;6.1.1.5 Aframe, housing the indicator, of such rigidity that a load of 15 N applied to the housing, out
22、 of contact with the presserfoot spindle (or any weight attached thereto), will produce a deflection of the frame not greater than the smallest scale divisionor digital count on the indicator;6.1.1.6 If employed, a dial diameter of at least 50 mm and graduated continuously to read directly to the ne
23、arest 2.5 m. Thedial can be equipped with a revolution counter that displays the number of complete revolutions of the large hand, or6.1.1.7 An electronic instrument having a digital readout in place of the dial indicator if that instrument meets all of the otherrequirements of this guide, and6.1.1.
24、8 The force applied to the presser foot spindle and the force necessary to register a change in the indicator reading shallbe less than the force that will cause deformation of the specimen. The force applied to the presser foot spindle and the forcenecessary to just prevent a change in the indicato
25、r reading shall be more than the minimum permissible force specified for aspecimen.6.2 Apparatus AManually Operated Thickness Gauge:6.2.1 An instrument having a presser foot and spindle that is manually lifted and lowered.6.3 Apparatus BAutomatically Operated Thickness Gauge:6.3.1 A pneumatic or mot
26、or-operated instrument having a presser foot spindle that is lifted and lowered either by a pneumaticcylinder or by a constant-speed motor through a mechanical linkage such that the rate of descent (for a specified range of distancesbetween the presser foot surface and anvil) and dwell time on the s
27、pecimen are within the limits specified for the material beingmeasured.6.3.2 A preferred drop rate between 0.750 and 1.500 mm/s between 0.625 and 0.025 mm on the dial and a capacity of at least0.775 mm.6.4 Apparatus CManually Operated Thickness Gauge with Linear Optical Encoder:6.4.1 Similar to Appa
28、ratus A except it employs a digital device with an electronic readout capable of repeatable readings towithin 6 1 m at zero setting or on a steel gauge block and a linear optical encoder using a scale of increments not less than 100lines/mm and capable of reading within 0.5 m with a 10 mm range.6.5
29、Apparatus DAutomatically Operated Thickness Gauge with Digital Display:6.5.1 Similar to Apparatus B except it employs an electronic device with a digital readout capable of a resolution not less than0.5 m and repeatable readings to within 6 1 m at zero setting or on a steel gauge block.6.5.2 A prefe
30、rred drop rate between 0.750 and 1.500 mm/s between 0.625 and 0.025 mm on the dial and a capacity of at least0.775 mm.D6988 1326.6 Other Instruments:6.6.1 Other instruments are commercially available that utilize different methods of measuring thickness. These are generallynon-contact devices employ
31、ing ultrasonic response, electrical capacitance, or similar material properties that can be correlated tothickness. Some of these devices are also designed to provide a means of measuring discreet sections of film in a continuousscanning mode. Instruments of this nature are acceptable provided they
32、meet or exceed the precision requirements noted in thispractice and the requirements of the applicable material or product specifications or applicable test standards.7. Test Specimens7.1 The test specimens shall be prepared from plastic films that have been cut to the required dimensions according
33、to PracticeD6287.7.2 Allow specimens to equilibrate at 23 6 2C (73.4 6 3.6F) and 50 6 10 % relative humidity in accordance with ProcedureA of Practice D618 unless otherwise specified by agreement or the relevant ASTM material specification.7.3 Unless otherwise specified, make all dimension measureme
34、nts at the same conditions used for equilibration.7.4 For each specimen, take precautions to prevent damage or contamination that will adversely affect the measurements.8. Procedure8.1 General Guidelines:NOTE 7In this section, the word “method” denotes a combination of both a specific apparatus and
35、a procedure describing its use.8.1.1 The selection of a method for measurement of film thickness is influenced by the characteristics of the film formeasurement. Each material and, in some cases, film construction in the case of multi-layer structures, will differ in its responseto test method param
36、eters, which include, but are not limited to, compressibility, rate of loading, ultimate load, dwell time, anddimensions of the presser foot and anvil. For a specific plastic material or structure, these responses can, in some cases, causemeasurements made using one method to differ significantly fr
37、om measurements made using another method. The effects due todifferences in elasticity are addressed in Appendix X1.TABLE 1 Instrument GuidelinesMethod Diameter of PresserFoot or Spindle, mmA Pressure on Specimen,Approximate, kPaBA 3.2 to 12.7 160 to 185B 3.2 to 12.7 160 to 185C 3.2 to 12.7 160 to 1
38、85D 3.2 to 12.7 160 to 185A It is known that the diameters of the pressure foot and spindle can influence the results. Data obtained from instruments with different geometries may not be comparable.B The total force applied to the specimen shall be less than the force that will cause permanent defor
39、mation or distortion of the specimen. For very thin or deformable films,a practical pressure range of 5 to 70 kPa has been found to be suitable.NOTE 8The pressure exerted by the gauge on the specimen being measured shall not distort or deform the specimen. For thin films, 0.025 mm0.001 in., or films
40、 which exhibit visual deformation during measurement, a maximum pressure of 70 kPa 10 psi is suggested. For thicker or stifferfilms, a pressure range between 160 and 185 kPa 23 and 27 psi is suggested. See Table 1.NOTE 9An electronic gauge can be substituted for the dial gauge in MethodAor B if the
41、presser foot and anvil meet the requirements of that method.8.1.2 The presence of contaminating substances on the surfaces of the test specimens, presser foot, anvil, or spindle can interferewith dimension measurements and result in erroneous readings. To help prevent this interference, select only
42、clean specimens fortesting, and keep them and the dimension measuring instrument covered until ready to make measurements. (WarningCleaningthe presser foot and anvil surfaces as described in X2.1 can cause damage to digital electronic gauges resulting in very expensiverepairs by the instrument manuf
43、acturer. Obtain procedures for cleaning such electronic gauges from the instrument manufacturerto prevent these costs.)8.1.3 One thickness determination per specimen or the average thickness determined by a continuous scanning instrument isacceptable if it can be demonstrated that the overall thickn
44、ess does not deviate 6 10 % from the average. This is especiallyapplicable if measurements are being made for reference, that is, to report nominal film thickness, and are not required for thedetermination of specific properties.8.1.4 Some instruments do not require calibration. For these instrument
45、s, periodic verification procedures should be conductedaccording to the recommendations of the instrument supplier.8.2 Method A:8.2.1 Using Apparatus A and specimens in conformance with Section 7, place the instrument on a solid, level, clean table orbench that is free of excessive vibration. Confir
46、m that the anvil and presser foot surfaces are clean. Adjust the zero point.8.2.2 Lower the presser foot on an area of the specimen for measurement. Observe 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 r
47、eading approximately 0.007 to 0.010mm higher than the initial reading of 8.2.2.8.2.5 Drop the foot onto the specimen (see Warning in 8.1.2).D6988 133NOTE 10This procedure minimizes small errors present when the pressure foot is lowered slowly onto the specimen and does not allow the presserfoot to s
48、eat properly.8.2.6 Observe the reading. After correcting the observed indicated dimension, record the corrected dimension value. A methodfor developing a calibration correction curve is described in X2.4.8.2.7 Move the specimen to another measurement position, and repeat the steps given in 8.2.3 thr
49、ough 8.2.6.8.2.8 Unless otherwise specified, make and record at least three dimension measurements on each specimen. The arithmeticmean of all dimension values is the dimension of the specimen.8.2.9 Recheck the instrument zero setting after measuring each specimen. If a change is observed, this is usually indicative ofcontamination on the contact surfaces and will require cleaning. (See Warning in 8.1.2 and Note 9.)8.3 Method B:8.3.1 Using Apparatus B and specimens in conformance with Section 7, place the instrument on a solid, level, clea
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