1、Designation: D2176 16Standard Test Method forFolding Endurance of Paper and Plastics Film by the M.I.T.Tester1This standard is issued under the fixed designation D2176; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This test method describes the us
3、e of the M.I.T.-typefolding apparatus for determining folding endurance of paperand plastics film. The M.I.T. tester can be adjusted for samplesof any thickness; however, if the outer layers thicker than about0.25 mm (0.01 in.) rupture during the first few folds, the testloses its significance. The
4、procedure for the Schopper-typeapparatus is given in Test Method D643.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard1.3 This stand
5、ard 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 limitations prior to use.2. Referenced Documents2.1 AS
6、TM Standards:2D585 Practice for Sampling and Accepting a Single Lot ofPaper, Paperboard, Fiberboard, and Related Product(Withdrawn 2010)3D643 Test Method for Folding Endurance of Paper by theSchopper Tester (Withdrawn 2010)3D685 Practice for Conditioning Paper and Paper Productsfor TestingD1968 Term
7、inology Relating to Paper and Paper ProductsE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or Process3. Terminology3.1 Definitions shall be in accordance with TerminologyD1968 and the Dictionary of Paper.44. Significance and U
8、se4.1 The folding endurance is frequently used to estimate theability of the paper and plastics film to withstand repeatedbending, folding, and creasing.4.2 Folding endurance has also been found useful in mea-suring the deterioration of paper and plastics film upon aging.5. Apparatus5.1 Folding Test
9、er, consisting of:5.1.1 A spring-loaded clamping jaw constrained to movewithout rotation in a direction perpendicular to the axis ofrotation of the folding head specified below and having itsclamping surfaces in the plane of this axis. The load is appliedby a spring attached to the jaw assembly whic
10、h is easilyadjustable to provide any desired tension on the specimenwithin range of 4.9 to 14.72 N (500 to 1500 gf). The deflectionof the spring when loaded shall be at least 17 mm (0.67in.)/9.81 N, which is achieved by using a weight of 1 kg mass.5.1.2 An oscillating folding head supporting two smo
11、oth,cylindrical folding surfaces parallel to, and symmetricallyplaced with respect to, the axis of rotation. Each of the twofolding surfaces shall have a radius of curvature of 0.38 mm(0.015 6 0.001 in.) and a width of 19 mm (0.75 6 0.04 in).The distance separating the folding surfaces is greater th
12、an theuncompressed thickness of the specimen being tested by nomore than 0.25 mm (0.010 in.). The position of the axis ofrotation is midway between the common tangent planes of thetwo folding surfaces. The folding head is provided with aclamping jaw with its nearest edge not less than 9.5 mm (0.3751
13、This classification system is under the jurisdiction ofASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterials.Current edition approved Nov. 1, 2016. Published November 2016. Originallyapproved in 1956. Last previous edition approved in 2007 as
14、 D2176 - 97a(2007),which was withdrawn May 2010 and reinstated in November 2016. DOI: 10.1520/D2176-16.2For 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
15、 Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from Technological Association of the Pulp and Paper Industry(TAPPI), 15 Technology Parkway South, Suite 115, Peachtree Corners, GA 30092,http:/www.tappi.org.*A Su
16、mmary 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 States1in.) beyond the axis of rotation. The rotary oscillating move-ment of the head is such as to fold the specimen through anangle
17、 of 135 6 2, both to the right and to the left of theposition of the unfolded specimen.5.1.3 Various size folding heads are required for testingdifferent thicknesses of specimens. Heads available will ac-commodate thicknesses from 0 to 0.25 mm (0 to 0.01 in.), 0.25to 0.50 mm (0.01 to 0.02 in.), 0.50
18、 to 0.75 mm (0.02 to 0.03in.), 0.75 to 1.02 mm (0.03 to 0.04 in.), and 1.02 to 1.25 mm(0.04 to 0.05 in.).5.2 Power Driven Device, for imparting a rotary oscillatingmotion of 175 6 25 cycles/min to the folding clamp.5.3 Counter, for registering the number of double foldsrequired to break the specimen
19、 and a device to stop theinstrument when the specimen breaks.5.4 Strip Cutter, to cut 15-mm wide parallel strips within60.02 mm with clean edges.5.5 A means for controlling the temperature of the foldinghead so that, during folding, it does not increase more than0.5C. Temperature rises of this magni
20、tude will reduce therelative humidity at the fold by more than 2 % and the numberof folds by as much as 10 %.Acommon method for controllingthe temperature of the folding head is by allowing an exhaustfan to draw conditioned room air from air rapidly over both thespecimen and head. The fan shall be o
21、f the centrifugal type notless than 50 mm in diameter, mounted so that its inlet isadjacent to the folding head. Other methods that preventheating of the folding head within the tolerances specified areacceptable.6. Sampling6.1 Acceptance SamplingAcceptance sampling shall bedone in accordance with P
22、ractice D585.6.2 Sampling for Other PurposesThe sampling and thenumber of test specimens depends upon the purpose of thetesting. Practice E122 is recommended7. Conditioning7.1 Condition the samples as required in Practice D685.7.2 Folding endurance measurements are very sensitive tothe moisture cont
23、ent of the paper. It is most important toobserve all the requirements of Practice D685 with regard topreconditioning from the dry side, conditioning, and maintain-ing the conditioned environment for testing when makingfolding endurance measurements.8. Test Specimen8.1 From each conditioned test unit
24、 cut ten specimensaccurately and cleanly to a width of 15 6 0.02 mm and a lengthof not less than 130 mm, and preferably 150 mm or longer ineach of the principal directions. Test specimens must be cutfree of wrinkles or blemishes. The portion of the test specimenwhere folding will occur must be free
25、of any portion of awatermark and have opacity and formation typical of thesample. Because the folding process occurs over a very shortlength of the total test specimen (that is, at the line of fold),data precision is heavily dependent upon the care taken in testspecimen selection and preparation.9.
26、Instrument Maintenance and Calibration9.1 The folding test results are very sensitive to tension, arcof fold, and radius of fold; therefore it is essential that regularcalibration routines be established and followed.9.2 Make sure that the folding edges are free from rust,nicks, dirt, and oil and th
27、at the counter operates properly.9.3 Measure the plunger friction by determining the addi-tional load required to move the plunger perceptibly under aload of 9.81 N or the load tension used for the testing. Thisshall not be greater than 0.245 N (25 gf).9.4 The change in tension due to the eccentrici
28、ty of rotationof the folding edges is measured as follows: Place a testspecimen of the proper thickness, cut in the machine direction,in the tester as for making a folding test, and apply a tension of9.81 N or that to be used for the testing. Rotate the folding headslowly by hand throughout the enti
29、re folding cycle andmeasure the maximum change in displacement of the plungerwith an accuracy of 0.1 mm (0.004 in.). This displacementshall not be greater than that produced by adding a weightequivalent to 0.343 N (35 gf).NOTE 1The displacement must be equally centered around theplunger position whe
30、n the strip of specimen is straight and the tension is9.81 N, that is, when the slot in the following head is vertical.9.5 The curvature of the folding edges can be measured bymaking casts, magnifying them in profile, and comparing themto true circles.9.6 The two folding edges shall be at the same e
31、levationwhen the slot head is vertical.10. Procedure10.1 Perform testing in an atmosphere in accordance withPractice D685. Handle the test specimens only by the ends,taking care not to touch them in the region in which they willbe folded.10.2 Turn the oscillating folding head so that the opening isv
32、ertical. Turn the motor control switch to the off position. Placea 1-kg weight on the top of the plunger (equivalent to thetension desired on the specimen); tap the plunger sideways tominimize friction effects and lock it in position. Withouttouching the part of the strip to be folded, clamp the spe
33、cimenlying wholly within one plane, that is, flat, and with the sides,parallel to, and not touching the oscillating jaw-mounting-plate. Remove the weight and unscrew the plunger lock toapply the specified tension to the test strip. If the reading of theload indicator changes, reclamp the specimen to
34、 give it itsproper tension. Zero counter, then start motor.NOTE 2The number of the folds vary by as much as the cube of theapplied tension. Use a tension of 9.81 N (1 kgf), but if this gives anunreasonably high or low test result, use more or less tension: 14.72 N or4.9 N (1.5 or 0.5 kgf) and state
35、the actual tension used in a prominentposition in the report.10.3 Set the counter to zero and place the centrifugal fan sothat its inlet is almost touching and is across the specimen andD2176 162oscillating head. Start the fan and the instrument motor. Foldthe strip at a uniform rate of 175 6 25 dou
36、ble folds per minuteuntil it breaks. Record the number of double folds made beforefracture. If there is any appreciable delay between tests onsuccessive specimens, keep the fan running to prevent the headwarming by conduction from its shaft.11. Report11.1 For each test specimen record the number of
37、doublefolds for the machine and cross directions. Convert the rawdata to the logarithm (base 10). Calculate the mean of the logsand report as log10MIT folding endurance for each directionseparately, to two significant figures for the mantissa. Stateclearly if a tension other than 9.81 N (1 kgf) was
38、used. Includethe number of specimens tested, and the standard deviation ofthe log10of the fold number obtained in each direction.11.2 Alternate report permitted. Although the preferredmethod for reporting MIT folding endurance is that in 11.1,analternate procedure of reporting the mean of the number
39、 ofdouble folds and the standard deviation for the machine andcross directions of the specimen separately is permitted.11.3 Tests made on strips having their length in the machinedirection are designated as being the “machine direction,” andsimilarly for the cross direction.12. Precision and Bias12.
40、1 Precision:12.1.1 The repeatability standard deviation for folding en-durance of paper has been determined to be 20 % and thereproducibility standard deviation for folding endurance hasbeen determined to be 28 %.12.1.2 The repeatability standard deviation for folding en-durance of plastic film has
41、been determined to be 15 % and thereproducibility standard deviation for folding endurance hasbeen determined to be 20 %.12.2 Bias:12.2.1 No information can be presented regarding the biasof fold endurance by the M.I.T. tester, as the measured value isdefined by the procedure in the test method. No
42、information isgiven regarding the bias between folding endurance as mea-sured in this test method using the M.I.T. tester and thatmeasured in Test Method D643 using the Schopper Testerbecause the instruments apply folding stress to the test speci-men in different ways and the relationship between re
43、sults bythe two procedures is not a constant value.13. Keywords13.1 fold number; folding endurance; paper; plastics filmSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue(D2176-97a(2007) that may impact the use of this standard. (Nov
44、ember 1, 2016)(1) Added “Plastics Film” in Title.(2) Added “plastics film”, and delete last sentence in 1.1.(3) Re-wrote 4.1.(4) Added “plastics film” in 4.2.(5) Changed “paper” to “specimen” in 5.1.2 and 5.1.3.(6) Changed “should” to “shall” in 5.5.(7) Deleted “from paper” and “not inherent in pape
45、r” in 8.1.(8) Deleted “of strong paper” in 9.4.(9) Changed “paper” to “specimen” in Note 1.(10) Deleted “may” in Note 2.(11) Re-wrote 12.1.2 for plastics film.(12) Deleted 12.1.3, 12.1.3.1, and 12.1.4.(13) Added “plastics film” in 13.1.ASTM International takes no position respecting the validity of
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