1、Designation: D7474 12D7474 17Standard Practice forDetermining Residual Stresses in Extruded or MoldedSulfone Plastic (SP) Parts by Immersion in VariousChemical Reagents1This standard is issued under the fixed designation D7474; the number immediately following the designation indicates the year ofor
2、iginal adoption 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. Scope*1.1 This practice covers the evaluation of residual stresses in
3、extruded profile or molded SP parts. The presence and relativemagnitude of residual stresses are indicated by the crazing of the specimen part upon immersion in one or more of a series ofchemical reagents. The specified chemical reagents were previously calibrated by use of Environmental Stress Crac
4、king (ESC)techniques to cause crazing in sulfone plastics (SP) at specified stress levels.1.2 This practice applies only to unfilled injection molding and extrusion grade materials of high molecular weight as indicatedby the following melt flow rates: PSU 9 g/10 min, max., PESU 30 g/10 m, max, and P
5、PSU 25 g/10 min, max. Lower molecularweight (higher melt flow) materials will craze at lower stress levels than indicated in Tables 1-3. (See Specification D6394 for meltflow rate conditions.)1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are fo
6、r information only.NOTE 1There is no known ISO equivalent for this standard.1.4 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 appropriate safety safety, health and healthenviron
7、mental practices and determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Gu
8、ides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D543 Practices for Evaluating the Resistance of Plastics to Chemical ReagentsD618 Practice for Conditioning Plastics for TestingD883 Terminology Relat
9、ing to PlasticsD4000 Classification System for Specifying Plastic MaterialsD6394 Specification for Sulfone Plastics (SP)2.2 ISO Standard:3ISO 220883 PlasticsDetermination of Resistance to Environmental Stress Cracking (ESC)Part 3: Bent Strip Method3. Terminology3.1 DefinitionsFor definitions of tech
10、nical terms pertaining to plastics used in this practice, see Terminology D883.4. Summary of Practice4.1 The practice involves the exposure of finished plastic parts to a specified series of chemical reagents which are known toproduce cracking or crazing of Sulfone Plastic (SP) materials at specific
11、 stress levels, under otherwise constant conditionsincluding a fixed time of one minute. Thus, the exposure of finished parts to one or more chemical reagents under no load1 This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20
12、.15 on Thermoplastic Materials.Current edition approved April 1, 2012Aug. 15, 2017. Published May 2012August 2017. Originally approved in 2008. Last previous edition approved in 20082012 asD7474 - 08.D7474 - 12. DOI:10.1520/D7474-12. DOI:10.1520/D7474-17.2 For referencedASTM standards, visit theASTM
13、 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.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 100
14、36, http:/www.ansi.org.This document 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
15、users consult prior editions as 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 Con
16、shohocken, PA 19428-2959. United States1conditions allows the quantification of the residual stress levels in the finished parts. Since the evaluation is based on the subjectivecriteria of presence or absence of crazing, this practice only yields an approximate indication of the level of residual st
17、resses inthe parts. This practice estimates the relative magnitude of residual stresses in parts produced from the series of sulfone plastics,namely polysulfone (PSU), polyethersulfone (PESU), and polyphenylsulfone (PPSU) materials.5. Significance and Use5.1 Thermoplastic moldings contain residual s
18、tresses due to differential cooling rates through the thickness of the molding.Changes in residual stress have been found to occur with time after molding due to stress relaxation. Many part performanceparameters as well as part failures are affected by the level of residual stress present in a part
19、. Residual stresses cause shrinkage,warpage, and a decrease in environmental stress crack resistance. This practice estimates the relative magnitude of residual stressesin parts produced from the series of sulfone plastics (SP), namely polysulfone (PSU), polyethersulfone (PESU), andpolyphenylsulfone
20、 (PPSU) materials.5.2 No direct correlation has been established between the results of the determination of residual stresses by this practice andpart performance properties. For this reason, this practice is not recommended as a substitute for other tests, nor is it intended foruse in purchasing s
21、pecifications for parts. Despite this limitation, this practice does yield information of value in indicating thepresence of residual stresses and the relative quality of plastic parts.5.3 Residual stresses cannot be easily calculated, hence it is important to have an experimental method, such as th
22、is practice,to estimate residual stresses.5.4 This practice is useful for extruders and molders who wish to evaluate residual stresses in SP parts. This can beaccomplished by visual examination after immersion in one or more chemical reagents to evaluate whether or not cracking occurs.Stresses will
23、relax after molding or extrusion. Accordingly, both immersion in the test medium and visual examination must bemade at identical times and conditions after processing, if comparing parts. It is important to note the differences in part history.Thus, this technique may be used is suitable as an indic
24、ation for quality of plastic processing.5.5 The practice is useful primarily for indicating residual stresses near the surface.6. Apparatus6.1 Container, of sufficient size to ensure complete immersion of specimen(s).6.2 Cotton swaps, patches or similar means to apply reagent to a localized area if
25、immersion is impractical.7. Reagents7.1 Ethanol, or Ethyl Alcohol, denatured,7.2 Ethyl acetate (EA),7.3 Methyl Ethyl Ketone (MEK), andTABLE 1 Liquid Reagents for Residual Stress Test for PSUMixture Mixture Composition Critical Stress, MPa (psi)% by volume Ethanol % by volume Ethyl Acetate1 50 50 15.
26、2 (2200)2 43 57 12.1 (1750)3 37 63 9.0 (1300)4 25 75 5.5 (800)TABLE 2 Liquid Reagents for Residual Stress Test for PESUMixture Mixture Composition Critical Stress, MPa (psi)% by volume Ethanol % by volume MEK1 50 50 17.9 (2600)2 40 60 10.3 (1500)3 20 80 6.9 (1000)4 0 100 5.9 (850)TABLE 3 Liquid Reag
27、ents for Residual Stress Test for PPSUMixture Mixture Composition Critical Stress, MPa (psi)% by volume Ethanol % by volume MEK1 50 50 22.8 (3300)2 25 75 13.8 (2000)3 10 90 9.0 (1300)4 0 100 8.0 (1150)D7474 1727.4 Isopropyl alcohol, 70 %.8. Safety Precaustions8.1 Protective Use protective equipment
28、and clothing must be utilized to avoid contact of chemical reagents with the skin oreyes. Use adequate ventilation to remove noxious or toxic fumes, or both.9. Test Specimen9.1 Size of SpecimenThe specimen shall be a complete molding or a cut piece of the extrusion or molding of sufficient sizeto no
29、t influence the stresses being observed. Twisting Avoid twisting and breaking must be avoided in when separating cut piecessincebecause the slightest amount of such forces has the potential to change stresses and cause false results.10. Conditioning10.1 It is not necessary to condition the part prio
30、r to testing by this practice. If conditioning is utilized for a controlled studyin a series of parts, recommended conditioning is at 23 6 2C (73.4 6 3.6F) and 50 6then condition the test specimens inaccordance with Procedure A of Practice D618 10 % relative humidity for a minimum of 40 hours prior
31、to testing. 4 h beforeperforming the test.10.2 Test ConditionsConduct tests in the standard laboratory atmosphere of 23 6 2C (73.4 6 3.6F) and 50 6 10 % relativehumidity, unless otherwise specified by the contract or relevant ASTM material specification.10.3 Residual stresses from molding decrease w
32、ith time after fabrication. For some studies, it is necessary to test as soon aspossible after molding. In such cases, allow the part to cool before testing.11. Procedure11.1 Choose the appropriate table from Tables 1-3, which list the series of chemical reagents that shall to be used for SP partsma
33、de from PSU, PESU and PPSU, respectively. Ensure that the required reagents are available.11.2 Rinse the specimen with isopropyl alcohol and air dry. Starting at the highest critical stress level (1), immerse the specimenfor one minute in the liquid reagent listed in the appropriate Table. Immediate
34、ly after immersion rinse the specimen with water,wipe dry and dry further by blowing low-pressure compressed air on the surface as needed.11.3 Inspect the part for cracked or crazed regions.NOTE 2Hairline fractures are often difficult to see at times.see.11.4 If the part is crazed, the residual stre
35、ss is greater than the critical stress value indicated for that reagent in the Table. Tableand is reported as being greater than that stress value. If the part is not crazed, the residual stress is less than the critical stress valueindicated, and the test is continued with the next liquid reagent i
36、n the Table.11.5 Using the same specimen, immerse the specimen in the next lower critical stress liquid reagent (2) for one minute, rinsewith water, dry and inspect for crazing. If crazing does not occur, the residual stress is less than the threshold for this liquid reagent,and the test is continue
37、d with the next liquid reagent.11.6 Continue until crazing occurs, or the last liquid reagent in the table is reached and no crazing occurs. If crazing does notoccur with the last reagent, then the residual stress value is below the last value in the table and shall be reported as being belowthat va
38、lue. Otherwise, the residual stress is reported to be between the last level that crazing did occur and the passing level.NOTE 3To maintain accurate stress readings, the reagents must be fresh. Over time, the reagents have been known to absorb water, evaporate, degradewhen exposed to light, or becom
39、e contaminated, which can lead to erroneous stress indications.NOTE 4Determining stress levels through the use of reagent exposure is approximate in nature. Residual stress levels depend on numerous moldingparameters which at times have been found to be unstable during molding. For this reason, indi
40、vidual specimens have been found to exhibit variationsin stress levels. Therefore, testing multiple parts is recommended.NOTE 5It is recommended that the determination of an acceptable molded-in stress level for an individual part be made from its end use application,in particular, the chemical envi
41、ronment to which the part will be exposed. Parts whose residual stress levels are below 6 to 8 MPa are typically consideredto be well molded.NOTE 6Exposure for time periods longer than one minute produces cracking at stress levels lower than those observed for one minute exposure.12. Report12.1 Repo
42、rt the following information:12.1.1 Identification of the type of material tested,12.1.2 Identification of the specimen, including whether extruded or molded, and cut specimen or complete,12.1.3 Time between molding or extrusion of parts and initial immersion,12.1.4 Conditioning,12.1.5 Liquid reagen
43、ts used,12.1.6 Estimated range of residual stress for the specimen tested,12.1.7 Date of test, andD7474 17312.1.8 Test practice number and published/revision date.13. Keywords13.1 liquid reagent; PESU; PPSU; PSU; residual stress; SP; stress crackingAPPENDIX(Nonmandatory Information)X1. CALIBRATION O
44、F STRESS LEVELS ASSOCIATED WITH EACH CHEMICAL REAGENTX1.1 The solvent mixtures and stress levels at which they cause crazing were determined using environmental stress crackingtechniques as described in ISO 22088-3 and are shown in Tables 1-3 in the main body of this practice, which apply to SP part
45、sproduced from PSU, PESU, and PPSU, respectively.X1.2 The stress level required for crazing to occur for each liquid reagent mixture was determined using annealed specimensexposed for one minute at known stress levels. ASTM flexural bar specimens were annealed for 1 hour at temperatures specifiedfor
46、 HDTspecimens in Specification D6394 to remove any stresses other than caused later by flexural strain during the ISO 22088-3test.X1.3 The parts being tested were conditioned at 23 6 2C (73.4 6 3.6F) andin accordance with Procedure A of Practice D61850 6 10 % relative humidity for a minimum of 40 ho
47、urs prior to testing.X1.4 Several methods have been found useful for applying the solvents; swiping with a cotton swab, immersion, or cotton patcheslaid on top. In most cases, cotton patches were laid on the surface of the specimen and then soaked the patch with the solventcombination. In all applic
48、ations the exposure time was one minute. After the time requirement was met the patches were removedand any residual solvent wiped off.X1.5 The mounted specimens were examined for crazing. The strain level at which crazing started was noted. Then from thecritical strain and the modulus of the materi
49、al being tested the critical stress was calculated for inclusion in Tables 1-3.X1.6 The tabulated information in Tables 1-3 was generated at room temperature temperature, as defined in 3.1.1 of PracticeD618, with a one-minute exposure time using annealed flexural bars.SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue(D7474 - 08D7474 - 12) that may impact the use of this standard. (April 1, 2012)(August 15, 2017)(1) MEK Conditioning section (10.1) changed to agree with conditioning requirements i
