1、Designation: F1473 13F1473 16Standard 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
2、, 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. Scope*1.1 This test method determines the resistance of polyethylene materials to slow c
3、rack growth under conditions specified within.NOTE 1This test method is known as PENT (Pennsylvania Notch Test) 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 with otherstresses low enough to preclude ductile failure and thereby eve
4、ntually induce brittle type of failure. Generally, polyethylenes willultimately fail in a brittle manner by slow crack growth at 80C if the stress is below 2.4 MPa.1.3 The test method is for specimens cut from compression molded plaques.2 See Appendix X1 for information relating tospecimens from pip
5、e.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish
6、 appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1600 Terminology for Abbreviated Terms Relating to PlasticsD4703 Practice for Compression Molding Thermoplastic Materials into Test Specimens, Pl
7、aques, or SheetsF412 Terminology Relating to Plastic Piping Systems3. Terminology3.1 Definitions are in accordance with Terminology F412. Abbreviations are in accordance with Terminology D1600, unlessotherwise indicated.3.2 Definitions:3.1.1 Definitions are in accordance with Terminology F412. Abbre
8、viations are in accordance with Terminology D1600, unlessotherwise indicated.3.2.1 brittle failurea pipe failure mode which exhibits no visible (to the naked eye) permanent material deformation(stretching, elongation, or necking down) in the area of the break (Terminology F412).3.3 Definitions of Te
9、rms Specific to This Standard:3.3.1 slow crack growththe slow extension of the crack with time.4. Summary of Test Method4.1 Specimens are prepared from compression molded plaques, precisely notched and then exposed to a constant tensile stressat elevated temperatures in air. Time on test is recorded
10、 for tests conducted against a minimum time before failure requirement orthe time to complete failure is recorded.1 This test method is under the jurisdiction of ASTM Committee F17 on Plastic Piping Systems and is the direct responsibility of Subcommittee F17.40 on Test Methods.Current edition appro
11、ved Aug. 1, 2013Aug. 15, 2016. Published August 2013August 2016. Originally approved in 1997. Last previous edition approved in 20112013 asF1473 11.F1473 13. DOI: 10.1520/F1473-13.10.1520/F1473-16.2 Lu, X., and Brown, N., “A Test for Slow Crack Growth Failure in Polyethylene Under a Constant Load,”
12、Journal of Polymer Testing, Vol 11, pp. 309319, 1992.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This doc
13、ument is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as
14、 appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*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. Unite
15、d States1NOTE 2Minimum time before failure requirements are found in material or product specifications, codes, etc.5. Significance and Use5.1 This test method is useful to measure the slow crack growth resistance of molded plaques of polyethylene materials ataccelerated conditions such as 80C, 2.4-
16、MPa stress, and with a sharp notch.5.2 The testing time or time to failure depends on the following test parameters: temperature; stress; notch depth; and specimengeometry. Increasing temperature, stress, and notch depth decrease the time to failure. Thus, in reporting the test time or time tofailur
17、e, all the conditions of the test shall be specified.6. Apparatus6.1 Lever Loading Machine, with a lever arm ratio of about 5:1.The tensile load may also be applied directly using dead weightsor any other method for producing a constant load. The pull rods on the grips shall have universal action to
18、 prevent bending. Thegrips shall be serrated to prevent slippage. The load on the specimen shall be accurate to at least 60.5 %.6.2 Furnace, heated by ordinary incandescent light bulbs covered with aluminum foil or any other suitable heating element.6.3 Temperature Controller, shall be able to contr
19、ol the temperature within 60.5C with respect to the set point.6.4 Temperature-Measuring Device, a thermometer or a thermocouple which can measure the temperature with an accuracybetter than 0.5C.6.5 Timer, shall have an accuracy of at least 1 % and shall automatically stop when the specimen fails.6.
20、6 Alignment Jig, as shown in Fig. 1, which aligns the grips and the specimen when the specimen is being tightened in the grips.Alignment jigs which produce the same function may be used.6.7 Notching Machine , for notching the specimen is shown in Fig. 2 or other machines which produce the same resul
21、ts maybe used. The notching machine presses a razor blade into the specimen at a speed less than 0.25 mm/min. The depth of the notchis controlled within60.01 mm. The machine is designed so that the main notch and the side notches will be coplanar and the planeof the notching is perpendicular to the
22、tensile axis of the specimen. The thickness of the razor blade is approximately 0.2 mm.7. Precautions7.1 The load shall be carefully added to avoid shocking the specimen. When the specimen is inserted in the grips, bending andtwisting shall be avoided in order to prevent the premature activation of
23、the notch. Avoid exposure to fluids such as detergents.8. Test Specimens8.1 Specimens are machined from a compression molded plaque of the polyethylene material.8.2 Specimen GeometryA representative geometry for compression molded plaque specimens is shown in Fig. 3.8.3 Dimensional Requirements:8.3.
24、1 The side groove shall be 1.0 6 0.10 mm for all plaque thicknesses.FIG. 1 Alignment JigF1473 1628.3.2 The overall length is not critical except that the distance between the notch and the end of a grip should be more than 10mm. Thicker specimens should have a greater overall length so that the grip
25、ped area will be greater in order to avoid slippage inthe grip.8.4 Preparation of Compression Molded Plaques8.4.1 Polyethylene resins shall be evaluated by using specimens that are machined from compression molded plaques usingPractice D4703, except for the following procedures.After the resin is he
26、ated to 140 to 160C, apply and remove the pressure threetimes. Increase the temperature to 170 to 190C for 10 to 15 min without pressure.Then apply and remove the pressure three times.The specific temperatures that are used depend on the melt index of the resin, that is, a higher temperature for a l
27、ower melt index.The purpose of applying and removing the pressure is to eliminate voids. Turn off the heat and apply pressure. The time to coolbetween 130 and 90C shall be greater than 80 min. Alternatively, the time to cool from the molding temperature to about roomtemperature shall be greater than
28、 5 h. During cooling the pressure is allowed to decrease naturally.8.5 Specimen NotchingThe specimen has two types of notches, the main notch and two side notches. The side notches areusually referred to as “side grooves.” The depth requirements for these notches are given in Table 1. The main notch
29、 is producedby pressing a razor blade into the specimen at a speed of less than 0.25 mm/min. A fresh razor blade shall not be used for morethan three specimens and shall be used within one day. The rate of notching for the side grooves is not important. It is importantto make the side grooves coplan
30、ar with the main notch. Specimens shall be notched at room temperature.9. Conditioning9.1 Unless otherwise specified, hold the test specimens for at least 1 h at the test temperature prior to loading. The length oftime between notching and testing is not important.10. Procedure10.1 Calculation of Te
31、st Load:10.1.1 Calculate the test load, P, as follows:P53w3t (1)FIG. 2 Notching MachineF1473 163where: = stress,w = specimen width, andt = specimen thickness.where: = stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the unnotched cross section. specimens prior
32、to notching.10.1.2 If has the units of megapascals and w and t are in millimetres, and A is in square millimetres, then P has the units ofNewtons. To convert Newtons to pounds, multiply by 0.225. If a lever-loaded machine is used, divide P by the lever arm ratio.The load on the specimen shall be 60.
33、5 % of the calculated load.10.2 Gripping the SpecimenUsing an alignment jig (Fig. 1), center the specimen in the grips so that the axis of the specimenis aligned with the grips. When the grips are tightened, it is important not to activate the notch by bending or twisting the specimen.The ends of th
34、e grips shall be at least 10 mm from the notch.Legend:Arrows designate direction of tensile stress.t = thickness.All dimensions are in millimetres.FIG. 3 Representative Geometry for Compression-Molded SpecimenTABLE 1 Notch Depth as a Function of Specimen ThicknessAThis table is based on the stress i
35、ntensity 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 4.4816.00 4.6517.00 4.8818.00 4.9519.00 5.0920.00 5.20A For an intermediate thickness, linearly interpolate to obtain
36、the notch depth. Thenotch depth in the specimen shall be within 0.05 mm of the interpolated value.F1473 16410.3 Loading the SpecimenWhen the specimen in the grips is removed from the alignment jig and transferred to the testingmachine, take care that the notch is not activated by bending the specime
37、n. Apply the load after the specimen has been held forat least 1 h at the test temperature.Apply the load gradually within a period of about 5 to 10 s without any impact on the specimen.10.4 Temperature MeasurementPlace the thermocouple or thermometer near the notched part of the specimen. Periodica
38、llyrecord the temperature with a frequency that depends on the length of the test.10.5 When testing is stopped before failure or when the specimen fails, record the time on test, or the time to failure. Failureoccurs when the two halves of the specimen separate completely or extensive deformation oc
39、curs in the remaining ligament.11. Report11.1 Compression-molded test specimens shall be identified by the polyethylene material source (resin manufacturer or othersource) and lot number.11.2 Stress based on the unnotched area.11.3 Depth of main notch and side grooves.11.4 Calculated load and cross-
40、sectional dimensions of the specimen.11.5 Test temperature.11.6 Time on 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 seven laboratories and used three resins from different producers. Thestand
41、ard deviation of the average values within laboratories is 616 %. The standard deviation of the average values betweenlaboratories is 626 %.12.2 BiasNo statement on bias can be made because there is no established reference value. The test method originated at theUniversity of Pennsylvania. If the t
42、est results from about eight years of testing at the University of Pennsylvania can be used asreference values, then there is no bias in the results from the different laboratories with respect to the results at the University ofPennsylvania. If the test results from the University of Pennsylvania c
43、an be used as a reference, then there is no bias for the roundrobin starting with pellets.413. Keywords13.1 fracture; notch testing; pipes; polyethylene; resin; slow crack growthANNEX(Mandatory Information)A1. MEASUREMENT OF SPECIMEN THICKNESS DIMENSIONA1.1 ScopeA1.1.1 The following procedures for m
44、easurement shall be used when required by the standard for the product being tested. Theserequirements are in addition to those in the main body of this test method.A1.2 Referenced DocumentsA1.2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for Testing4 Supporting data have been filed at
45、 ASTM International Headquarters and may be obtained by requesting Research Report RR:F17-1043. This report is based on a roundrobin of seven laboratories starting with pellets.F1473 165A1.3 ConditioningA1.3.1 Conditioning Temperature and HumidityCondition the test specimens in accordance with Pract
46、ice D618 Procedure Awithout regard for humidity unless otherwise specified by contract or when required by the standard for the product being tested.A1.4 ApparatusA1.4.1 The following apparatus shall be usedFlat-Anvil Micrometer with an accuracy of at least 6 0.001 in. (6 0.025 mm).A1.5 Dimensioning
47、A1.5.1 Measure the thickness of each specimen prior to notching to the nearest 0.001 in. (0.025 mm) at the center of eachspecimen.A1.5.2 If the thickness dimension has a required value in the standard for the product being tested, then report the thickness tothe same decimal place required by that s
48、tandard.A1.5.3 If the thickness dimension has a required precision in the standard for the product being tested, then report the precisionof the apparatus used for measurement.APPENDIX(Nonmandatory Information)X1. TESTING SPECIMENS FROM PIPEX1.1 ScopeTest Method F1473 has been used to measure the sl
49、ow crack growth resistance of specimens from pipe.X1.1.1 Test results are affected by size, specimen geometry, molecular orientation, and other processing effects.X1.1.2 Extrusion generally aligns polyethylene molecules parallel to the extrusion direction. Notching perpendicular to theextrusion direction (Fig. X1.1(a) generally gives higher results than notching parallel to the extrusion direction (Fig. X1.1(b).X1.1.3 Values obtained from tests of specimens cut from pipe can vary significantly from values obtained from tests of specimensmac
