1、Designation: F1473 18Standard Test Method forNotch Tensile Test to Measure the Resistance to Slow CrackGrowth of Polyethylene Pipes and Resins1This standard is issued under the fixed designation F1473; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 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. Scope*1.1 This test method determines the resistance of polyeth-ylene materials to slow crack gr
3、owth under conditions speci-fied within.NOTE 1This test method is known as PENT (Pennsylvania NotchTest) test.1.2 The test is generally performed at 80C and at 2.4 MPa,but may also be done at temperatures below 80C and withother stresses low enough to preclude ductile failure andthereby eventually i
4、nduce brittle type of failure. Generally,polyethylenes will ultimately fail in a brittle manner by slowcrack growth at 80C if the stress is below 2.4 MPa.1.3 The test method is for specimens cut from compressionmolded plaques.2See Appendix X1 for information relating tospecimens from pipe.1.4 The va
5、lues stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 s
6、afety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior 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
7、of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D1600 Terminology forAbbreviated Terms Relating to Plas-ticsD4703 Practice for Compression Molding ThermoplasticMateria
8、ls into Test Specimens, Plaques, or SheetsD5596 Test Method For Microscopic Evaluation of theDispersion of Carbon Black in Polyolefin GeosyntheticsF412 Terminology Relating to Plastic Piping Systems2.2 ISO Standard:4ISO 18553 Method for the assessment of the degree ofpigment or carbon black dispersi
9、on in polyolefin pipes,fittings and compounds3. Terminology3.1 Definitions are in accordance with Terminology F412.Abbreviations are in accordance with Terminology D1600,unless otherwise indicated.3.2 Definitions:3.2.1 brittle failurea pipe failure mode which exhibits novisible (to the naked eye) pe
10、rmanent material deformation(stretching, elongation, or necking down) in the area of thebreak (Terminology F412).3.3 Definitions of Terms Specific to This Standard:3.3.1 slow crack growththe slow extension of the crackwith time.4. Summary of Test Method4.1 Specimens are prepared from compression mol
11、dedplaques, precisely notched and then exposed to a constanttensile stress at elevated temperatures in air. Time on test is1This test method is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition
12、 approved Feb. 1, 2018. Published March 2018. Originallyapproved in 1997. Last previous edition approved in 2016 as F1473 16. DOI:10.1520/F1473-18.2Lu, X., and Brown, N., “ATest for Slow Crack Growth Failure in PolyethyleneUnder a Constant Load,” Journal of Polymer Testing, Vol 11, pp. 309319, 1992.
13、3For 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.4Available from International Organization for Standardizatio
14、n (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.*A Summary 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 St
15、atesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to T
16、rade (TBT) Committee.1recorded for tests conducted against a minimum time beforefailure requirement or the time to complete failure is recorded.NOTE 2Minimum time before failure requirements are found inmaterial or product specifications, codes, etc.5. Significance and Use5.1 This test method is use
17、ful to measure the slow crackgrowth resistance of molded plaques of polyethylene materialsat accelerated conditions such as 80C, 2.4-MPa stress, andwith a sharp notch.5.2 The testing time or time to failure depends on thefollowing test parameters: temperature; stress; notch depth; andspecimen geomet
18、ry. Increasing temperature, stress, and notchdepth decrease the time to failure. Material parameters, notcontrolled by the laboratory, that could impact the test results(time to failure) are: pigment (color or carbon black) and thecarrier resin for the pigment, or both. Thus, in reporting the testti
19、me or time to failure, all the conditions of the test shall bespecified.NOTE 3Time to failure can also be affected by the degree of pigment(color or carbon black) dispersion and distribution within the testspecimen. Test Method D5596 and ISO 18553 provide methods forassessing the degree of dispersio
20、n and distribution of the pigment6. Apparatus6.1 Lever Loading Machine, with a lever arm ratio of about5:1. The tensile load may also be applied directly using deadweights or any other method for producing a constant load.Thepull rods on the grips shall have universal action to preventbending. The g
21、rips shall be serrated to prevent slippage. Theload on the specimen shall be accurate to at least 60.5 %.6.2 Furnace, heated by ordinary incandescent light bulbscovered with aluminum foil or any other suitable heatingelement.6.3 Temperature Controller, shall be able to control thetemperature within
22、60.5C with respect to the set point.6.4 Temperature-Measuring Device, a thermometer or athermocouple which can measure the temperature with anaccuracy better than 0.5C.6.5 Timer, shall have an accuracy of at least 1 % and shallautomatically stop when the specimen fails.6.6 Alignment Jig, as shown in
23、 Fig. 1, which aligns the gripsand the specimen when the specimen is being tightened in thegrips.Alignment jigs which produce the same function may beused.6.7 Notching Machine , for notching the specimen is shownin Fig. 2 or other machines which produce the same resultsmay be used. The notching mach
24、ine presses a razor blade intothe specimen at a speed less than 0.25 mm/min. The depth ofthe notch is controlled within 60.01 mm. The machine isdesigned so that the main notch and the side notches will becoplanar and the plane of the notching is perpendicular to thetensile axis of the specimen. The
25、thickness of the razor blade isapproximately 0.2 mm.7. Precautions7.1 The load shall be carefully added to avoid shocking thespecimen. When the specimen is inserted in the grips, bendingand twisting shall be avoided in order to prevent the prematureactivation of the notch. Avoid exposure to fluids s
26、uch asdetergents.8. Test Specimens8.1 Specimens are machined from a compression moldedplaque of the polyethylene material.FIG. 1 Alignment JigFIG. 2 Notching MachineF1473 1828.2 Specimen GeometryA representative geometry forcompression molded plaque specimens is shown in Fig. 3.8.3 Dimensional Requi
27、rements:8.3.1 The side groove shall be 1.0 6 0.10 mm for all plaquethicknesses.8.3.2 The overall length is not critical except that thedistance between the notch and the end of a grip should bemore than 10 mm. Thicker specimens should have a greateroverall length so that the gripped area will be gre
28、ater in orderto avoid slippage in the grip.8.4 Preparation of Compression Molded Plaques8.4.1 Polyethylene resins shall be evaluated by usingspecimens that are machined from compression moldedplaques using Practice D4703, except for the following proce-dures. After the resin is heated to 140 to 160C
29、, apply andremove the pressure three times. Increase the temperature to170 to 190C for 10 to 15 min without pressure. Then applyand remove the pressure three times. The specific temperaturesthat are used depend on the melt index of the resin, that is, ahigher temperature for a lower melt index. The
30、purpose ofapplying and removing the pressure is to eliminate voids. Turnoff the heat and apply pressure. The time to cool between 130and 90C shall be greater than 80 min. Alternatively, the timeto cool from the molding temperature to about room tempera-ture shall be greater than 5 h. During cooling
31、the pressure isallowed to decrease naturally.8.5 Specimen NotchingThe specimen has two types ofnotches, the main notch and two side notches. The side notchesare usually referred to as “side grooves.” The depth require-ments for these notches are given in Table 1. The main notchis produced by pressin
32、g a razor blade into the specimen at aspeed of less than 0.25 mm/min. A fresh razor blade shall notbe used for more than three specimens and shall be used withinone day. The rate of notching for the side grooves is notimportant. It is important to make the side grooves coplanarwith the main notch. S
33、pecimens shall be notched at roomtemperature.9. Conditioning9.1 Unless otherwise specified, hold the test specimens forat least1hatthetest temperature prior to loading. The lengthof time between notching and testing is not important.10. Procedure10.1 Calculation of Test Load:10.1.1 Calculate the tes
34、t load, P, as follows:P 5 3w 3t (1)where: = stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the specimens prior tonotching.Legend:Arrows designate direction of tensile stress.t = thickness.All dimensions are in millimetres.FIG. 3 Representative Geometry for Co
35、mpression-Molded SpecimenTABLE 1 Notch Depth as a Function of Specimen ThicknessAThis table is based on the stress intensity being the same for allthicknesses.Thickness, mm Notch Depth, mm4.00 1.905.00 2.286.00 2.507.00 2.808.00 3.099.00 3.3010.00 3.5011.00 3.7012.00 3.9013.00 4.1814.00 4.3915.00 4.
36、4816.00 4.6517.00 4.8818.00 4.9519.00 5.0920.00 5.20AFor an intermediate thickness, linearly interpolate to obtain the notch depth. Thenotch depth in the specimen shall be within 0.05 mm of the interpolated value.F1473 18310.1.2 If has the units of megapascals and w and t are inmillimetres, and A is
37、 in square millimetres, then P has the unitsof Newtons. To convert Newtons to pounds, multiply by 0.225.If a lever-loaded machine is used, divide P by the lever armratio. The load on the specimen shall be 60.5 % of thecalculated load.10.2 Gripping the SpecimenUsing an alignment jig (Fig.1), center t
38、he specimen in the grips so that the axis of thespecimen is aligned with the grips. When the grips aretightened, it is important not to activate the notch by bendingor twisting the specimen. The ends of the grips shall be at least10 mm from the notch.10.3 Loading the SpecimenWhen the specimen in the
39、grips is removed from the alignment jig and transferred to thetesting machine, take care that the notch is not activated bybending the specimen. Apply the load after the specimen hasbeen held for at least1hatthetest temperature.Apply the loadgradually within a period of about 5 to 10 s without any i
40、mpacton the specimen.10.4 Temperature MeasurementPlace the thermocouple orthermometer near the notched part of the specimen. Periodi-cally record the temperature with a frequency that depends onthe length of the test.10.5 When testing is stopped before failure or when thespecimen fails, record the t
41、ime on test, or the time to failure.Failure occurs when the two halves of the specimen separatecompletely or extensive deformation occurs in the remainingligament.11. Report11.1 Compression-molded test specimens shall be identifiedby the polyethylene material source (resin manufacturer orother sourc
42、e) lot number as well as information of the color(for example, natural, black, blue etc.) of the specimen beingtested.11.2 Stress based on the unnotched area.11.3 Depth of main notch and side grooves.11.4 Calculated load and cross-sectional dimensions of thespecimen.11.5 Test temperature.11.6 Time o
43、n test or time to failure.11.7 Date and time for the beginning and ending of the test.12. Precision and Bias12.1 PrecisionA round robin was conducted with sevenlaboratories and used three resins from different producers. Thestandard deviation of the average values within laboratories is616 %. The st
44、andard deviation of the average values betweenlaboratories is 626 %.12.2 BiasNo statement on bias can be made because thereis no established reference value. The test method originated atthe University of Pennsylvania. If the test results from abouteight years of testing at the University of Pennsyl
45、vania can beused as reference values, then there is no bias in the resultsfrom the different laboratories with respect to the results at theUniversity of Pennsylvania. If the test results from the Univer-sity of Pennsylvania can be used as a reference, then there is nobias for the round robin starti
46、ng with pellets.513. Keywords13.1 fracture; notch testing; pipes; polyethylene; resin; slowcrack growthANNEX(Mandatory Information)A1. MEASUREMENT OF SPECIMEN THICKNESS DIMENSIONA1.1 ScopeA1.1.1 The following procedures for measurement shall beused when required by the standard for the product being
47、tested. These requirements are in addition to those in the mainbody of this test method.A1.2 Referenced DocumentsA1.2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingA1.3 ConditioningA1.3.1 Conditioning Temperature and HumidityCondition the test specimens in accordance with Prac
48、tice D618Procedure A without regard for humidity unless otherwisespecified by contract or when required by the standard for theproduct being tested.A1.4 ApparatusA1.4.1 The following apparatus shall be usedFlat-AnvilMicrometer with an accuracy of at least 6 0.001 in. (6 0.025mm).A1.5 DimensioningA1.
49、5.1 Measure the thickness of each specimen prior tonotching to the nearest 0.001 in. (0.025 mm) at the center ofeach specimen.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F17-1043. This report is based on around robin of seven laboratories starting with pellets.F1473 184A1.5.2 If the thickness dimension has a required value in thestandard for the product being tested, then report the thicknessto the same decimal place required by that standard.A1.5.3 If the thickness dimens
