ASTM D3826-2018 Standard Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test.pdf

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1、Designation: D3826 18Standard Practice forDetermining Degradation End Point in DegradablePolyethylene and Polypropylene Using a Tensile Test1This standard is issued under the fixed designation D3826; the number immediately following the designation indicates the year oforiginal adoption or, in the c

2、ase 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 practice covers the determination of a degradation-end point (a brittle point) for d

3、egradable polyethylene/polypropylene films and sheeting less than 1.0 mm (0.04 in.)thick. This practice is not intended for determination of the rateor degree of degradation of a polyethylene/polypropylene filmor sheet, but rather, to assess when in the course of itsdegradation under some condition,

4、 a brittle point is reached. Ifone wishes to monitor tensile elongation during the degrada-tion process (such as when the tensile elongation is signifi-cantly greater than 5 %), Test Method D882 is recommended.This practice is not to be considered the only way of deter-mining a degradation-end point

5、.1.2 Tensile properties of plastics 1.0 mm (0.04 in.) orgreater in thickness shall be determined in accordance withTest Method D638.1.3 Use a static weighing-constant rate of grip separationtest. This procedure employs a constant rate of separation ofthe grips holding the sample and a static load ce

6、ll.NOTE 1This procedure is based on the use of grip separation as ameasure of extension; however, the desirability of using extensionindicators accurate to 61.0 % or better as specified in Test Method D638is recognized, and a provision for the use of such instrumentation isincorporated in the proced

7、ure.1.4 This procedure has been successful for determining thedegradation end point of ethylene-carbon-monoxide copoly-mers and has screened successfully two other additive-typepolyethylenes in a round robin test.1.5 The values stated in SI units are to be regarded as thestandard. The values in pare

8、ntheses are for information only.1.6 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 re

9、gulatory limitations prior to use.1.7 There is no equivalent ISO standard.1.8 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 Re

10、com-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D374/D374M Test Methods for Thickness of Solid Electri-cal InsulationD618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties

11、of PlasticsD882 Test Method for Tensile Properties of Thin PlasticSheetingD883 Terminology Relating to PlasticsD5208 Practice for Fluorescent Ultraviolet (UV) Exposureof Photodegradable PlasticsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE691 Practice for Conducting an Inter

12、laboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of TermsFor definitions of terms used inthis specification associated with plastics issues refer to theterminology contained in Terminology D883.3.2 Definitions:3.2.1 Definitions of terms and symbols relating to

13、 tensiontesting of plastics appear in the Annex to Test Method D638.3.2.2 line grips, nin tensile testing machines, grips havingfaces designed to concentrate the entire gripping force along asingle line perpendicular to the direction of testing stress.3.2.3 tear failure, nin tensile testing of films

14、, a failurecharacterized by fracture initiating at one edge of the specimen1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.96 on Environmentally DegradablePlastics and Biobased Products.Current edition approved Nov. 1, 201

15、8. Published November 2018. Originallyapproved in 1991. Last previous edition approved in 2013 as D3826 98 (2013).DOI: 10.1520/D3826-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume in

16、formation, refer to the standards Document Summary page onthe ASTM website.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 standardiz

17、ation established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1and progressing across the specimen at a rate slow enough toproduce an anomalous load-deformat

18、ion curve.3.3 Definitions of Terms Specific to This Standard:3.3.1 film, nfor the purpose of this practice, a piece ofmaterial not exceeding 0.250 mm (0.01 in.) in thickness.3.3.2 brittle point, nin degradable polyethylene/polypropylene film, that point in the history of a material when75 % of the s

19、pecimens tested have a tensile elongation at breakof 5 % or less.4. Significance and Use4.1 The tensile elongation property determined by thispractice is of value for the characterization of degradablematerials. It is possible that the tensile elongation property willvary with specimen thickness, me

20、thod of preparation, speed oftesting, type of grips used, and manner of measuring testextension. Consequently, where precise comparative results aredesired, these factors must be carefully controlled.4.2 It is acceptable to use the tensile elongation property toprovide data for research and developm

21、ent and engineeringdesign as well as quality control specifications. However, datafrom such tests cannot be considered significant for applica-tions differing widely from the load-time scale of the testemployed.4.3 Materials that fail by tearing give anomalous data thatcannot be compared with those

22、from normal failure.4.4 Before proceeding with this test method, referenceneeds to be made to the specifications of the material beingtested. Any test specimen preparation, conditioning,dimensions, or testing parameters or a combination thereof,covered in the material specifications shall take prece

23、denceover those mentioned in this test method. If there are nomaterial specifications, then the default conditions apply.5. Apparatus5.1 Testing Machines:5.1.1 Use a testing machine of the constant rate-of-jaw-separation type. The machine shall be equipped with a weigh-ing system that moves a maximu

24、m distance of 2 % of thespecimen extension within the range being measured. Also,there needs to be a device for recording the tensile load and theamount of separation of the grips; both of these measuringsystems shall be accurate to 62 %. The rate of separation ofthe grips shall be uniform and capab

25、le of adjustment fromapproximately 1.3 to 500 mm/min (0.05 to 20 in./min) inincrements necessary to produce the strain rates specified in9.2.5.2 GripsUse a gripping system that minimizes bothslippage and uneven stress distribution with the test specimen.NOTE 2Grips lined with thin rubber, crocus-clo

26、th, or pressure-sensitive tape as well as file-faced or serrated grips have been successfullyused for many materials. The choice of grip surface depends on thematerial tested and thickness. More recently, line grips padded on theround face with 1.0 mm (40 mil) blotting paper have been found superior

27、.Air-actuated grips have been found advantageous, particularly in the caseof materials that tend to neck into the grips, since pressure is maintainedat all times. In cases where samples frequently fail at the edge of the grips,it is likely to be advantageous to increase slightly the radius of curvat

28、ureof the edges where the grips come in contact with the test area of thespecimen.5.3 Thickness GageA dead-weight dial micrometer asprescribed in Method C of Test Methods D374/D374M,reading to 0.0025 mm (0.0001 in.) or less.5.4 Width-Measuring DevicesSuitable test scales or otherwidth-measuring devi

29、ces capable of reading to 0.25 mm (0.010in.) or less.5.5 Specimen CutterFixtures incorporating razor blades,suitable paper cutters, or other devices capable of safely cuttingthe specimens to the proper width and producing straight,clean, parallel edges with no visible imperfections. A deviceconsisti

30、ng of two parallel knives mounted firmly against aprecision-ground base shear-block (similar to a paper cutter)has proved satisfactory. The use of striking dies is notrecommended because poor and it is possible that inconsistentspecimen edges will be produced. It is imperative that thecutting edges

31、be kept sharp and free from visible scratches ornicks.5.6 Extension IndicatorsIf employed, extension indicatorsshall conform to requirements specified in Test Method D638.In addition, such apparatus shall be so designed as to minimizestress on the specimen at the contact points of the specimen andth

32、e indicator.NOTE 3A high-response speed in the recording system is desirable,particularly when relatively high strain rates are employed for rigidmaterials. The speed of pen response for recorders is supplied bymanufacturers of this equipment. Take care to conduct tests at conditionssuch that respon

33、se time (ability of recorder to follow actual load) producesless than 2 % error.6. Test Specimen6.1 Cut test specimens prior to exposure. Take utmost carein cutting specimens to prevent nicks and tears that are likelyto cause premature failures (see Note 4). The edges shall beparallel to within 5 %

34、of the width over the length of thespecimen between the grips.NOTE 4Amicroscopic examination of the specimen is a potential wayto detect flaws due to sample or specimen preparation.6.2 Prepare the test specimen with uniform width andlength. Examples of typical lengths and widths are:Width, mm Length

35、, mm13 (0.5 in.) 152 (6 in.)25 (1.0 in.) 102 (4 in.)6.2.1 The test specimen thickness is contingent upon thethickness of the end-use application. The test specimen thick-ness needs to be the same as that for the specific end-useapplication.6.3 Wherever possible, select test specimen so that thick-ne

36、ss is uniform to within 10 % of the thickness over the lengthof the specimen between the grips in the case of materials 0.25mm/in. (0.010 in.) or less in thickness, and to within 5 % in thecase of materials greater than 0.25 mm (0.010 in.) in thicknessbut less than 1.00 mm (0.040 in.) in thickness.D

37、3826 182NOTE 5In cases where thickness variations are in excess of thoserecommended in 6.3, results may not be characteristic of the materialunder test.6.4 Whenever possible, cut test specimens and test in themachine direction only.7. Number of Test Specimens7.1 Take sufficient test specimens in the

38、 machine directionfrom each sample to ensure four acceptable measurements (see4.3, 7.2). Samples that break during degradation exposure canbe deemed to have absolute tensile elongations of less than 5 %(see 10.2).NOTE 6When exposing samples (especially outdoors) they willsometimes break up, and tens

39、ile tests cannot be properly performed. Forthis reason, broken samples are deemed to have reached 5 % absoluteelongation for the purpose of determining the brittle point.7.2 Discard specimens that fail at some obvious flaw, or thatfail outside the gage length, unless such flaws or conditionsconstitu

40、te a variable whose effect is being studied. However,jaw breaks (failures at the grip contact point) are acceptable ifit has been shown that results from such tests are in essentialagreement with values obtained from breaks occurring withinthe gage length.NOTE 7In the case of some materials, examina

41、tion of specimens priorto and following testing under crossed optical polarizers (polarizing films)provides a useful means of detecting flaws which may be responsible forpremature failure.8. Conditioning8.1 ConditioningCondition the test specimens at23 6 2C (73.4 6 3.6F) and 50 6 10 % relative humid

42、ity fornot less than 40 h prior to test in accordance with Procedure Aof Practice D618.8.2 Test ConditionsConduct tests in the standard labora-tory atmosphere of 23 6 2C (73.4 6 3.6F) and 50 6 10 %relative humidity.9. Procedure9.1 Set the initial grip separation that is appropriate for thedimensions

43、 of the test specimen.9.2 Set the rate of grip separation to provide an initial strainrate of 0.1 mm/mm min.9.3 Measure the thickness to an accuracy of 0.0025 mm(0.0001 in.) or better or films less than 0.25 mm (0.010 in.) inthickness and to an accuracy of 1 % or better for specimensgreater than 0.2

44、5 mm (0.010 in.) but less than 1.0 mm (0.040in.) in thickness.9.4 Place the test specimen in the grips of the testingmachine, taking care to align the long axis of the specimenwith an imaginary line joining the points of attachment of thegrips to the machine. Tighten the grips evenly and firmly to t

45、hedegree necessary to minimize slippage of the specimen duringthe test.10. Calculation10.1 Calculate the percentage elongation at break by divid-ing the elongation at the moment of rupture of the specimen bythe initial gage length of the specimen and multiplying by 100.When the gage marks or extenso

46、meters are used to define aspecific test section, use only this length. Report the result inpercent to two significant figures.10.2 The material is considered degraded to the brittle pointwhen 75 % or more of the test specimens have a tensileelongation of 5 % or less.11. Report11.1 Report the follow

47、ing information:11.1.1 Complete identification of the material tested, includ-ing type, source, manufacturers code number, form, principaldimensions, previous history, and orientation of samples withrespect to anisotropy (if any),11.1.2 Method of preparing test specimens,11.1.3 Thickness, width and

48、length of test specimens,11.1.4 Complete identification of exposure practice or pro-cedure used to degrade test specimens,11.1.5 Grip separation (initial),11.1.6 Crosshead speed (rate of grip separation),11.1.7 Gage length (if different from gage separation),11.1.8 Type of grips used, including faci

49、ng (if any),11.1.9 Conditioning procedure (test conditions,temperature, and relative humidity, if non-standard),11.1.10 Anomalous behavior such as tear failure and failureat a grip,11.1.11 Percentage elongation at break of each sample andthe number of samples that broke during exposure,11.1.12 Whether or not the specimens tested reached thebrittle point and the exposure time required to do so.11.1.13 Indicate whether an extensometer is employed.TABLE 1 Tensile Elongation at Break Determined According to Practice D3826Material Tested AverageRepeatability Sta