1、Designation: D 3826 98 (Reapproved 2008)Standard Practice forDetermining Degradation End Point in DegradablePolyethylene and Polypropylene Using a Tensile Test1This standard is issued under the fixed designation D 3826; the number immediately following the designation indicates the year oforiginal a
2、doption 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
3、brittle 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 u
4、nder 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 D 882 is recommended.This practice should not be considered the only way ofdetermining a d
5、egradation-end point.1.2 Tensile properties of plastics 1.0 mm (0.04 in.) orgreater in thickness shall be determined in accordance withTest Method D 638.1.3 Use a static weighing-constant rate of grip separationtest. This procedure employs a constant rate of separation ofthe grips holding the sample
6、 and 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 D 638is recognized, and a provision for the use of such instrumentation isinco
7、rporated 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 thestanda
8、rd. The 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
9、 of regulatory limitations prior to use.1.7 There is no equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 374 Test Methods for Thickness of Solid Electrical Insu-lationD 618 Practice for Conditioning Plastics for TestingD 638M Standard Test Method for Tensile Properties ofPlastics
10、 (Metric)3D 882 Test Method for Tensile Properties of Thin PlasticSheetingD 5208 Practice for Fluorescent Ultraviolet (UV) Exposureof Photodegradable PlasticsD 691 Discontinued 1981; Specification for CompoundPowdered Soap (Granulated, with Rosin)33. Terminology3.1 Definitions:3.1.1 Definitions of t
11、erms and symbols relating to tensiontesting of plastics appear in the Annex to Test Method D 638.3.1.2 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,
12、 nin tensile 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 Description of Terms Specific to This Standard:3.2.1 film, nfor the purpose of this prac
13、tice, 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.4. Significance and Use4.1 The tensil
14、e elongation property determined by thispractice is of value for the characterization of degradable1This 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 edit
15、ion approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1991. Last previous edition approved in 2002 as D 3826 98 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
16、e information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.materials. The tensile elongation property may vary withspecimen thickness, method of preparati
17、on, 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 property may be utilized toprovide data for research and development and engineeringdesign
18、 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 from normal failure.4.4 B
19、efore proceeding with this test method, referenceshould be made to the specifications of the material beingtested. Any test specimen preparation, conditioning, dimen-sions, or testing parameters or a combination thereof, coveredin the material specifications shall take precedence over thosementioned
20、 in this test method. If there are no materialspecifications, 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 maximum distance of 2 % of thes
21、pecimen 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 %. The rate of separation ofthe grips shall be uniform and capable of adjustment fromapprox
22、imately 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-cloth, or pressure-sensitive t
23、ape 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.Air-actuated grips have be
24、en 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 advantageous to increase slightly the radius of curvature of theedges where the grips come
25、 in contact with the test area of the specimen.5.3 Thickness GageA dead-weight dial micrometer asprescribed in Method C of Test Methods D 374, reading to0.0025 mm (0.0001 in.) or less.5.4 Width-Measuring DevicesSuitable test scales or otherwidth-measuring devices capable of reading to 0.25 mm (0.010
26、in.) 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 deviceconsisting of two parallel knives mounted firmly
27、 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 imperative that the cutting edges be keptsharp and free from visible scratches or nicks.5.6 Ex
28、tension IndicatorsIf employed, extension indica-tors shall conform to requirements specified in Test Method D638. In addition, such apparatus shall be so designed as tominimize stress on the specimen at the contact points of thespecimen and the indicator.NOTE 3A high-response speed in the recording
29、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 response time (ability of recorder to follow actual load) produ
30、cesless 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 % of the width over the length of thespecimen between the g
31、rips.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 are:Width, mm Length, mm13 (0.5 in.) 152 (6 in.)25 (1.0 in.) 102 (4 in.)6.2.1 The t
32、est 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 specimen so that thick-ness is uniform to within 10 % of the thickness over the lengthof t
33、he 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.NOTE 5In cases where thickness variations are in excess of thosere
34、commended 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 machine directionfrom each sample to ensure four acceptable measurements
35、(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 will some-times break up, and tensile tests can not be properly performed. For thisreason, broken samples
36、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 conditionsconstitute a variable whose effect is being studied. However,D 3826 98 (2008)2j
37、aw 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, examination of specimens priorto and following testing under
38、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 5 % relative humidity fornot less than 40 h prior to test in accordance w
39、ith Procedure Aof Practice D 618.8.2 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 appropriate for thedimensions of the test specimen.9.2 Set the rate of grip separatio
40、n 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 0.25 mm (0.010 in.) but less than 1.0 mm (0.040in.) in thic
41、kness.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 thedegree necessary to minimize slippage of the specimen
42、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 extensometers are used to define aspecific test section, use on
43、ly 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 following information:11.1.1 Complete identification of the ma
44、terial 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 length of test specimens,11.1.4 Complete identification
45、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 facing (if any),11.1.9 Conditioning procedure (test conditio
46、ns, tempera-ture, 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 poin
47、t 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 E 691 for three degradable polyolefin polymers pro-duced the repeatability and reproducibility results for tensileelonga
48、tion shown in Table 1. Each laboratory tested specimensthat were unexposed and specimens that had been exposed for240 h according to Practice D 5208 (Cycle A).413. Keywords13.1 brittle point; degradable plastics; plastics;polyethylene/polypropylene films/sheeting; tensile elongation4Supporting data
49、available at ASTM Headquarters. Request RR: D 20.TABLE 1 Tensile Elongation at Break Determined According to Practice D 3826Material 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 96.0 410.2white LLDPE, exposed 240 hB1.4 0.5 1.0 1.4 2.6AECO material is an ethyl
