1、Designation: F 1473 07An American National StandardStandard Test Method forNotch Tensile Test to Measure the Resistance to Slow CrackGrowth of Polyethylene Pipes and Resins1This standard is issued under the fixed designation F 1473; the number immediately following the designation indicates the year
2、 oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the resistance of polyeth-y
3、lene materials to slow crack growth 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
4、failure andthereby eventually induce 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 t
5、ospecimens from pipe.1.4 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 regulatory limitations prior t
6、o use.2. Referenced Documents2.1 ASTM Standards:3D 618 Practice for Conditioning Plastics for TestingD 1600 Terminology for Abbreviated Terms Relating toPlasticsD 3350 Specification for Polyethylene Plastics Pipe andFittings MaterialsD 4703 Practice for Compression Molding ThermoplasticMaterials int
7、o Test Specimens, Plaques, or SheetsF 412 Terminology Relating to Plastic Piping Systems3. Terminology3.1 Definitions:3.1.1 Definitions are in accordance with Terminology F 412.Abbreviations are in accordance with Terminology D 1600,unless otherwise indicated.3.1.2 brittle failurea pipe failure mode
8、 which exhibits novisible (to the naked eye) permanent material deformation(stretching, elongation, or necking down) in the area of thebreak (Terminology F 412).3.2 Definitions of Terms Specific to This Standard:3.2.1 slow crack growththe slow extension of the crackwith time.4. Summary of Test Metho
9、d4.1 Specimens are cut from compression molded plaques. Itis precisely notched and then exposed to a constant tensilestress at elevated temperatures in air. The time for completefailure is recorded.5. Significance and Use5.1 This test method is useful to measure the slow crackgrowth resistance of mo
10、lded plaques of polyethylene materialsat accelerated conditions such as 80C, 2.4-MPa stress, andwith a sharp notch.5.2 The time to failure depends on the following testparameters: temperature; stress; notch depth; and specimengeometry. Increasing temperature, stress, and notch depthdecrease the time
11、 to failure. Thus, in reporting the time tofailure, all the conditions of the test must be specified.6. 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 r
12、ods on the grips shall have universal action to preventbending. The grips 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.1This
13、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 approved May 1, 2007. Published May 2007. Originallyapproved in 1997. Last previous edition approved in 2001 as F 1473 01e1.2Lu,
14、 X., and Brown, N., “ATest for Slow Crack Growth Failure in PolyethyleneUnder a Constant Load,” Journal of Polymer Testing, Vol 11, pp. 309319, 1992.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
15、rds volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Temperature Controller, shall be able to control thetemperature within 60.5C with respect to
16、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 Fig. 1, which aligns
17、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 machine presses a razor b
18、lade 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 thickness of the razo
19、r 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 such asdetergents.8. T
20、est Specimens8.1 Specimens are machined from a compression moldedplaque of the polyethylene material.8.2 Specimen GeometryA representative geometry forcompression molded plaque specimens is shown in Fig. 3.8.3 Dimensional Requirements:8.3.1 The side groove shall be 1.0 6 0.10 mm for all plaquethickn
21、esses.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 greater in orderto avoid slippage in the grip.8.4 Preparation of Compression
22、 Molded PlaquesPolyethylene resins shall be evaluated by using specimens thatare machined from compression molded plaques using PracticeD 4703, except for the following procedures. After the resin isheated to 140 to 160C, apply and remove the pressure threetimes. Increase the temperature to 170 to 1
23、90C for 10 to 15min without pressure. Then apply and remove the pressurethree times. The specific temperatures that are used depend onthe melt index of the resin, that is, a higher temperature for alower melt index. The purpose of applying and removing thepressure is to eliminate voids. Turn off the
24、 heat and applypressure. The time to cool between 130 and 90C shall begreater than 80 min. Alternatively, the time to cool from themolding temperature to about room temperarture shall begreater than 5 h. During cooling the pressure is allowed todecrease naturally.8.5 Specimen NotchingThe specimen ha
25、s 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 pressing a razor blade into the specimen at aspeed of less than 0.25 mm/min. A fresh raz
26、or 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. Specimens shall be notched at roomtemperature.FIG. 1 Alignment JigFIG. 2 Notching
27、MachineF 1473 0729. 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 test load, P, as follows:P 5s3w
28、 3 t (1)where:s = stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the unnotched crosssection.10.1.2 If s has the units of megapascals and w and t are inmillimetres, and A is in square millimetres, then P has the unitsof Newtons. To convert Newtons to pounds, m
29、ultiply 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 the specimen in the grips so that the axis of thespecimen is aligned with the grips. Whe
30、n 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 thegrips is removed from the alignment jig and transferred to thetesting machine, take car
31、e 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 impacton the specimen.10.4 Temperature MeasurementPlace the thermocoupleor thermometer n
32、ear the notched part of the specimen. Peri-odically record the temperature with a frequency that dependson the length of the test.10.5 When the specimen fails, record the time to failure.Failure occurs when the two halves of the specimen separatecompletely or extensive deformation occurs in the rema
33、iningligament.11. Report11.1 Compression-molded test specimens shall be identifiedby the polyethylene material source (resin manufacturer orother source) 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-sectional dimensio
34、ns of thespecimen.11.5 Test temperature.11.6 Time to failure.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 o
35、n 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 4.4816.00 4.6517.00 4.8818.00 4.9519.00 5.0920.00 5.20AFor an intermediate thickness, linearly interpola
36、te to obtain the notch depth.The notch depth in the specimen shall be within6 0.05 mm of the interpolatedvalue.F 1473 07311.7 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 diffe
37、rent producers. Thestandard deviation of the average values within laboratories is616 %. The standard 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
38、Pennsylvania. If the test results from abouteight years of testing at the University of Pennsylvania 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-s
39、ity of Pennsylvania can be used as a reference, then there is nobias for the round robin starting with pellets.413. Keywords13.1 fracture; notch testing; pipes; polyethylene; resin; slowcrack growthAPPENDIX(Nonmandatory Information)X1. TESTING SPECIMENS FROM PIPEX1.1 ScopeTest Method F 1473 has been
40、 used to measurethe slow 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 moleculesparallel to the extrusion direction. Notching perpendicular
41、tothe extrusion direction (Fig. X1.1(a) generally gives higherresults than notching parallel to the extrusion direction (Fig.X1.1(b).X1.1.3 Values obtained from tests of specimens cut frompipe can vary significantly from values obtained from tests ofspecimens machined from a compression molded plaqu
42、e of theresin.X1.2 Significance and UseTest results may be useful forresearch, or for comparison or evaluation of resin or processingeffects on slow crack growth resistance.X1.2.1 While the resin is the primary factor in slow crackgrowth resistance, when tests are conducted on specimens frompipe, pi
43、pe size, pipe wall thickness, extrusion equipment, andprocessing can affect test results. These influences can beaddressed by consistency and uniformity in preparing, loading,and notching specimens. This is especially important whentesting is for the purpose of evaluation or comparison.NOTE X1.1Many
44、 combinations of different types of extrusion equip-ment, tooling, and processing conditions are used to extrude polyethylenepipe. Differences in extrusion equipment, tooling, and processing condi-tions are known to affect the results when specimens cut from pipe aretested in accordance with this te
45、st method.X1.3 Specimen Preparation:X1.3.1 When a section of the pipe wall is to be tested, cutsections or strips from the pipe. Sections or strips should be cut4 to 6 mm wider than the required specimen width, thendeburred, and machined to the specimen width.X1.3.2 Fig. X1.1(a) illustrates a specim
46、en cut from 4 in. IPSSDR 11 pipe where the load direction axis is parallel to theextrusion direction and the main notch is perpendicular to theextrusion direction. Fig. X1.1(b) illustrates a specimen from 4in. IPS SDR 11 pipe where the load direction axis is perpen-dicular to the extrusion direction
47、 axis (parallel to the hoopdirection) and the main notch is parallel to the extrusiondirection. Fig. X1.1(c) illustrates a specimen for pipe diametersless than 25 mm.X1.3.3 Sawing, cutting, machining, or milling operationsshould be carefully performed to avoid overheating the speci-men.X1.3.4 Remode
48、lingPipe may be remolded by cuttingchips from the pipe, then preparing a compression moldedplaque in accordance with 8.4 or by flattening a section of pipe,then heating, pressing, and cooling the flattened section inaccordance with 8.4. When remolded, most extrusion process-ing effects will be remov
49、ed, therefore, the results obtained fromremolded plaques will differ from the results obtained fromas-extruded pipe.X1.4 Specimen Dimensions:X1.4.1 The overall length of the specimen is not criticalprovided that the distance between the notch and the end of thegrip should be more than 10 mm. Thicker specimens shouldhave a greater overall length to provide sufficient grip area andto avoid slippage in the grip. The gripped area should bemachined to a flat bar so that the grip does not introducebending stresses.X1.4.1.1 See Table X1.1 for suggested specimen
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