1、Designation: D3826 98 (Reapproved 2013)Standard 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 ado
2、ption or, 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 practice covers the determination of a degradation-end point (a br
3、ittle point) for degradable polyethylene/polypropylene films and sheeting less than 1.0 mm (0.04 in.)thick. This practice is not intended for determination of the rateof degree of degradation of a polyethylene/polypropylene filmor sheet, but rather, to assess when in the course of itsdegradation und
4、er some condition, 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 should not be considered the only way ofdetermining a degr
5、adation-end point.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
6、 a static load cell.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 isincorpora
7、ted in the procedure.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. T
8、he values in parentheses 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 and health practices and determine the applica-bility of r
9、egulatory limitations prior to use.1.7 There is no equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lation (Withdrawn 2013)3D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of Plastic
10、sD882 Test Method for Tensile Properties of Thin PlasticSheetingD5208 Practice for Fluorescent Ultraviolet (UV) Exposureof Photodegradable PlasticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 Definitions of terms
11、and symbols relating to tensiontesting of plastics appear in the Annex to Test Method D638.3.1.2 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.3.1.3 tear failure, nin t
12、ensile testing of films, a failurecharacterized by fracture initiating at one edge of the specimenand progressing across the specimen at a rate slow enough toproduce an anomalous load-deformation curve.3.2 Definitions of Terms Specific to This Standard:3.2.1 film, nfor the purpose of this practice,
13、a piece ofmaterial not exceeding 0.250 mm (0.01 in.) in thickness.3.2.2 brittle point, nin degradable polyethylene/polypropylene film, that point in the history of a material when75 % of the specimens tested have a tensile elongation at breakof 5 % or less.1This practice is under the jurisdiction of
14、ASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.96 on Environmentally DegradablePlastics and Biobased Products.Current edition approved Feb. 1, 2013. Published February 2013. Originallyapproved in 1991. Last previous edition approved in 2008 as D3826 98 (2008).DOI:
15、 10.1520/D3826-98R13.2For 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 Document Summary page onthe ASTM website.3The last approved version of this histo
16、rical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 The tensile elongation property determined by thispractice is of value for the characterization of degradablemateri
17、als. The tensile elongation property may vary withspecimen thickness, method of preparation, speed of testing,type of grips used, and manner of measuring test extension.Consequently, where precise comparative results are desired,these factors must be carefully controlled.4.2 The tensile elongation p
18、roperty may be utilized toprovide data for research and development 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 b
19、y tearing give anomalous data thatcannot be compared with those from normal failure.4.4 Before proceeding with this test method, referenceshould be made to the specifications of the material beingtested. Any test specimen preparation, conditioning,dimensions, or testing parameters or a combination t
20、hereof,covered in the material specifications shall take precedenceover 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
21、 shall be equipped with a weigh-ing system that moves a maximum distance of 2 % of thespecimen extension within the range being measured. Also,there should be a device for recording the tensile load and theamount of separation of the grips; both of these measuringsystems shall be accurate to 62 %. T
22、he rate of separation ofthe grips shall be uniform and capable 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
23、test specimen.NOTE 2Grips lined with thin rubber, crocus-cloth, 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
24、with 1.0 mm (40 mil) blotting paper have been found superior.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 may be adv
25、antageous to increase slightly the radius of curvature of theedges where the grips come in contact with the test area of the specimen.5.3 Thickness GageA dead-weight dial micrometer asprescribed in Method C of Test Methods D374, reading to0.0025 mm (0.0001 in.) or less.5.4 Width-Measuring DevicesSui
26、table test scales or otherwidth-measuring devices 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 w
27、ith no visible imperfections. A deviceconsisting 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 inconsistent specimen edgesmay be produced. It is imperati
28、ve that the cutting edges be keptsharp and free from visible scratches or nicks.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 po
29、ints of the specimen andthe 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
30、conditionssuch that response 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
31、 beparallel to within 5 % of the width over the length of thespecimen between the grips.NOTE 4A microscopic examination of the specimen may be used todetect flaws due to sample or specimen preparation.6.2 Prepare the test specimen with uniform width andlength. Examples of typical lengths and widths
32、are:Width, mm Length, 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 should be the same as that for the specific end-useapplication.6.3 Wherever possible, select test specime
33、n so that thick-ness 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 i
34、n.) in thickness.NOTE 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 specime
35、ns in the 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).D3826 98 (2013)2NOTE 6When exposing samples (especially outdoors) they willsom
36、etimes break up, and tensile tests can not 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 f
37、laws or conditionsconstitute 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
38、of some materials, examination 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) an
39、d 50 6 5 % relative humidity 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 5%relative humidity.9. Procedure9.1 Set the initial grip separation that is approp
40、riate for thedimensions 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 sp
41、ecimensgreater than 0.25 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
42、 evenly and firmly to thedegree 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 th
43、e gage marks or extensometers 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. Repor
44、t11.1 Report the following 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.
45、3 Thickness, width and 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 gri
46、ps used, including facing (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
47、 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.12. Precision and Bias12.1 A round robin conducted and analyzed according toPractice E691 for three degradable polyolefin polyme
48、rs pro-duced the repeatability and reproducibility results for tensileelongation shown in Table 1. Each laboratory tested specimensthat were unexposed and specimens that had been exposed for240 h according to Practice D5208 (Cycle A).413. Keywords13.1 brittle point; degradable plastics; plastics;pol
49、yethylene/polypropylene films/sheeting; tensile elongation4Supporting data available at ASTM Headquarters. Request RR: RR:D20-1233.TABLE 1 Tensile Elongation at Break Determined According to Practice D3826Material Tested AverageRepeatability StandardDeviation, SrReproducibility StandardDeviation, SRRepeatability Limit,rReproducibility Limit,RECO,Aunexposed 282.4 41.6 138.8 166.8 388.7ECO, exposed 240 hB2.5 1.8 2.1 5.1 6.0clear LLDPE,Cunexposed 371.4 40.1 231.3 112.3 647.7clear LLDPE, exposed 240 hB6.5 5.1 5.8 14.2 16.3white LLDPE, unexposed 235.4 34.3 146.5
