ASTM D8136-17 Standard Test Method for Determining Plastic Film Thickness and Thickness Variability Using a Non-Contact Capacitance Thickness Gauge.pdf

1、Designation: D8136 17Standard Test Method forDetermining Plastic Film Thickness and ThicknessVariability Using a Non-Contact Capacitance ThicknessGauge1This standard is issued under the fixed designation D8136; the number immediately following the designation indicates the year oforiginal adoption o

2、r, 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. Scope1.1 This test method covers the determination of the thick-ness of plastic film, r

3、anging in thickness from 2.5 to 250 m,with a non-contact thickness gauge that uses capacitance-basedtechnology. It includes a method to generate a series ofthickness data points that can be used to characterize thevariability patterns of film for both transverse or machinedirection (profiling).NOTE

4、1Thicker specimens, typically 250 m to 2500 m thick, canutilize this test method if the apparatus is designed to measure and handlematerials of this thickness range, and the apparatus complies with therequirements as defined in this standard.1.2 This test method provides a method for buyers andselle

5、rs of film to communicate the thickness and pattern ofthickness variability of the product they are buying/selling.1.3 This test method does not apply to textured or porousfilms or films that are conductive or coated with a conductivesubstance.NOTE 2Films that contain excessive levels of anti-static

6、 additive canbe conductive and need to be tested to verify that they do not cause anegative reading on the instrument.1.4 UnitsThe values stated in SI units are to be regardedas the standard. No other units of measurement are included inthis standard.NOTE 3There is no known ISO equivalent to this st

7、andard.1.5 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 standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior

8、 to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBar

9、riers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1505 Test Method for Density of Plastics by the Density-Gradient TechniqueD4805 Terminology for Plastics Standards (Withdrawn2002)3D6988

10、Guide for Determination of Thickness of Plastic FilmTest SpecimensE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE252 Test Method for Thickness of Foil, Thin Sheet, andFilm by Mass MeasurementE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of

11、 a Test Method2.2 ISO Standard:ISO 472 PlasticsVocabulary43. Terminology3.1 DefinitionsSee Terminologies D883, D4805, D6988,and ISO 472 for definitions pertinent to this test method.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration, nset of operations that establishes, un-der spec

12、ified conditions, the relationship between values mea-sured or indicated by an instrument or system and the corre-sponding reference standard or known values derived from theappropriate reference standards.1This is under the jurisdiction of ASTM Committee D20 on Plastics and is thedirect responsibil

13、ity of Subcommittee D20.19 on Film, Sheeting, and MoldedProducts.Current edition approved Sept. 1, 2017. Published September 2017. DOI:10.1520/D8136-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSta

14、ndards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.or

15、g.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of Int

16、ernational Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.2 calibration recipe, ncomputer-stored calibration thatrelates the response of the instrument to a thickness or basisweight of a given specimen.3.2.3 guide posts,

17、nposts that protrude from the front faceof a profiler apparatus that apply tension and help guide thespecimen as it is profiled.3.2.4 guide tray, ntray, which can also include a weightthat is placed on top of the film, that protrudes from the frontface of a profiler apparatus that applies tension an

18、d helps guidethe specimen as it is profiled.3.2.5 leader, npiece of film that is attached to the leadingedge of the specimen to bridge the distance from the edge ofthe specimen being measured to the drive roller of an auto-mated profiler allowing the user to measure as close to the edgeof the specim

19、en as possible (see Fig. 1).3.2.6 loop tensioner, ndevice that places tension on a loopof film, typically produced when making blown film, to flattenthe film as it is pulled through the profiler.3.2.7 machine direction, ndirection of the flow of the filmout of the extrusion die.3.2.7.1 DiscussionIt

20、is also commonly referred to as the“downweb direction” (see Fig. 2).3.2.8 measurement footprint, narea over which the capaci-tance response is measured.3.2.9 non-contact capacitance thickness gauge,ninstrument that measures the thickness of a specimenwithout touching it by sensing the capacitance re

21、sponse createdby the material when placed in an electric field.3.2.10 profiling, vobtaining an array of data points, eachpoint being the average thickness under the measurement area,across a specimen (see Fig. 3).3.2.11 spooling, noptional feature offered on some profil-ers that automatically wraps

22、the film around a take-up rollerafter the film has been profiled.3.2.11.1 DiscussionIt is typically used to facilitate thehandling of long specimens.3.2.12 trailer, npiece of material attached to the trailingedge of the specimen that is being profiled.3.2.12.1 DiscussionThis material helps maintain

23、consis-tent tension on the film as it is pulled through the device (seeFig. 4).FIG. 1 Leader Attached to a Specimen with TapeFIG. 2 Illustration of the Machine/Downweb Direction and the Transverse/Crossweb DirectionD8136 1723.2.13 transverse direction, ndirection perpendicular tothe flow of the film

24、 out of the extrusion die.3.2.13.1 DiscussionIt is also commonly referred to as the“crossweb direction” (see Fig. 2).3.2.14 verification, nproof, with the use of calibratedstandards or standard reference materials, that the calibratedinstrument is operating within specified requirements.4. Summary o

25、f Test Method4.1 This test method describes a non-contact method formeasuring the thickness of plastic film using a capacitance-based gauging system and provides a guide for profiling filmthickness variability in the transverse and machine directions.4.2 This test method explains how to prepare and

26、calibratethe instrument properly.4.3 This test method explains how to prepare the specimensproperly.4.4 The first procedure option describes profiling a filmspecimen. A strip is cut from a film roll and thicknessmeasurements are made along the strip to characterize thematerials thickness and pattern

27、 of thickness variability.FIG. 3 Profiling a Film Specimen and the Resulting Graph and DataFIG. 4 Trailer Attached to the Specimen with TapeD8136 1734.5 The second procedure option describes using the instru-ment to measure a single area on the film.5. Significance and Use5.1 This test method provid

28、es precise dimensions necessaryfor the calculation of properties expressed in physical units.5.2 This test method provides a means to characterize thevariability of the material thickness in the transverse andmachine directions for quality control purposes, productionprocess support and analysis, in

29、coming product inspection andfor defining variability for buying/selling film.5.3 This test method provides a method for instrumentcalibration utilizing traceable standards available from theNational Institute of Standards and Technology (NIST).5.4 It is not intended to replace other thickness measu

30、re-ments based on commercial portable tools, nor is it implied thatthickness measurements made by different procedures willexactly agree.6. Apparatus6.1 A non-contact capacitance gauge that is linear (60.5 %over the thickness range of materials being measured as testedin accordance with Appendix X2)

31、 in its response and exhibitsa precision of 60.1 m, or 60.5 % of material thickness(whichever is larger) when used with standard referencematerials.NOTE 4This can be verified using a 25 m specimen and verifyingthat it reads the same when measured twice to 60.1 m.6.2 Measurement Footprint:6.2.1 For p

32、rofiling a specimen, the optimal measurementfootprint is rectangular in area with an opposing directionlength to an in-line length ratio of 5 to 1 or greater, such thatthe aspect ratio enhances the resolution of the measurement inthe direction of the profile (transverse or machine) whileaveraging th

33、e variability in the perpendicular direction.NOTE 5When profiling a specimen, each measurement is the averageof the entire measurement area. To define the variability in a specifieddirection, the variability is measured at higher resolution than theopposing direction. This averages a wider distance

34、in the opposingdirection while giving fine detail in the desired direction. This provides aline average with a high resolution in the direction of the profile and helpsto isolate the variability in the desired direction (see Fig. 5).6.2.2 In comparing this approach to previous standards thattypicall

35、y use a circular shape footprint, a data point using therectangular footprint is similar to taking and averaging multiplesingle-point measurements perpendicular to the direction beingprofiled. A typical measurement area for a profiler is 3.2 mmwide by 57.2 mm long (see Fig. 6).6.2.3 For a device des

36、igned for spot measurements, acircular or rectangular footprint is used.6.3 A means is used to convey the film through themeasurement head with an encoded data acquisition to auto-matically (preferred) or manually acquire and plot data points.It is recommended that this process be automated as thist

37、ypically produces better repeatability and reproducibility re-sults.6.4 Provide proper shielding for the measurement sensor sothat objects near or touching the device probe do not affect thereading.6.5 The data collection software shall have the capability tocalibrate the instrument, store calibrati

38、on recipes, control theinstrument, and record and present the data.7. Hazards7.1 In an automated film profiler, avoid pinch points wherethe two rollers come together to create friction on the driveroller. Do not place fingers between the rollers and keep looseclothing, hair, or other objects from en

39、tering the rollers.8. Test Specimens8.1 Preparing a Specimen for a Profile Measurement:8.1.1 Prepare the specimen by cutting a strip to the widthspecified by the equipment manufacturer to ensure that theentire measurement surface is covered during the profilingoperation. For a transverse direction s

40、pecimen, it is recom-mended that the entire extruded width of the material beprofiled to characterize the variability pattern across the entirewidth of the extrusion die. For a machine direction specimen,the user needs to select a specimen length based on theirprocess conditions. Additional informat

41、ion on determining thismachine direction specimen length is provided in Appendix X2(see Figs. 7 and 8).NOTE 6It is recommended that the material be cut using a template soFIG. 5 Measurement Footprint Orientation Relative to Profile DirectionD8136 174that the length and width are easy to obtain and c

42、onsistent across thespecimen.8.1.2 In some cases, the resulting specimen is a continuousloop of material. In other cases, a specimen will be a strip ofmaterial. To measure the ends of a specimen that is not acontinuous loop, a leader and trailer (see Fig. 9) attached to thespecimen with tape, can be

43、 used. For a proper characterizationof variability, it is necessary to measure as much of thespecimen as possible.NOTE 7When running strip with a leader and a trailer, typicallymissing 1 cm along the ends is acceptable because of the space requiredto attach the tape.8.2 Preparing a Specimen for a Sp

44、ot Measurement:NOTE 8Non-contact profilers are typically used for profiling a strip ofmaterial but can also be used to do spot measurements, similarly to acontact micrometer as discussed in Guide D6988.8.2.1 The test specimens shall be prepared from plastic filmthat have been cut to the required dim

45、ensions consistent to thedesign requirements of the gauging system as recommended bythe manufacturer.8.3 For each specimen, take precautions to prevent damageor contamination that will adversely affect the measurements.NOTE 9Avoid creasing the material as this can cause a reading error.8.4 Allow spe

46、cimens to equilibrate at 23 6 2C and 50 610 % relative humidity in accordance with Procedure A ofPractice D618 unless otherwise specified by agreement or therelevant ASTM International material specification.8.5 Unless otherwise specified, make all dimension mea-surements at the same conditions used

47、 for equilibration.9. Preparation of Apparatus9.1 Turn on the instrument and allow it to stabilize for atime period as specified by the manufacturer.NOTE 10At least1histypically required for the equipment tostabilize. It is common for users to leave the device on continuously toavoid this stabilizat

48、ion period.9.2 Set the device to read zero with no specimen in themeasurement area.9.3 Verify proper operation of the gauge using a referencespecimen (as specified in Annex A4) and the followingprocedure:9.3.1 Load the calibration recipe for the reference specimen.9.3.2 Insert the reference specimen

49、 into its specifiedposition, and Confirm that it reads the correct value.9.4 Choose the calibration recipe for the material composi-tion being tested from the calibration table or calibrate thedevice using a method specified in Section 10.10. Calibration and Standardization10.1 Calibration is necessary for each material compositiontested because material composition will determine the dielec-tric response.NOTE 11This is necessary as the device indirectly measures thicknessby measuring the dielectric response of the mate