ASTM_D_7474_-_12.pdf

Designation:D747412Standard 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 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()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This practice covers the evaluation of residual stressesin extruded profile or molded SP parts.The presence andrelative magnitude of residual stresses are indicated by thecrazing of the specimen part upon immersion in one or more ofa series of chemical reagents.The specified chemical reagentswere previously calibrated by use of Environmental StressCracking(ESC)techniques to cause crazing in sulfone plastics(SP)at specified stress levels.1.2 This practice applies only to unfilled injection moldingand extrusion grade materials of high molecular weight asindicated by the following melt flow rates:PSU 9 g/10 min,max.,PESU 30 g/10 m,max,and PPSU 25 g/10 min,max.Lower molecular weight(higher melt flow)materials will crazeat lower stress levels than indicated in Tables 1-3.(SeeSpecification D6394 for melt flow rate conditions.)1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.NOTE1There is no known ISO equivalent for this standard.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 to use.2.Referenced Documents2.1 ASTM Standards:2D543 Practices for Evaluating the Resistance of Plastics toChemical ReagentsD883 Terminology Relating to PlasticsD4000 Classification System for Specifying Plastic Materi-alsD6394 Specification for Sulfone Plastics(SP)2.2 ISO Standard:3ISO 220883 PlasticsDetermination of Resistance to En-vironmental Stress Cracking(ESC)Part 3:Bent StripMethod3.Terminology3.1 DefinitionsFor definitions of technical terms pertain-ing to plastics used in this practice,see Terminology D883.4.Summary of Practice4.1 The practice involves the exposure of finished plasticparts to a specified series of chemical reagents which areknown to produce cracking or crazing of Sulfone Plastic(SP)materials at specific stress levels,under otherwise constantconditions including a fixed time of one minute.Thus,theexposure of finished parts to one or more chemical reagentsunder no load conditions allows the quantification of theresidual stress levels in the finished parts.Since the evaluationis based on the subjective criteria of presence or absence ofcrazing,this practice only yields an approximate indication ofthe level of residual stresses in the parts.This practiceestimates the relative magnitude of residual stresses in partsproduced from the series of sulfone plastics,namely polysul-fone(PSU),polyethersulfone(PESU),and polyphenylsulfone(PPSU)materials.5.Significance and Use5.1 Thermoplastic moldings contain residual stresses due todifferential cooling rates through the thickness of the molding.Changes in residual stress have been found to occur with timeafter molding due to stress relaxation.Many part performanceparameters as well as part failures are affected by the level ofresidual stress present in a part.Residual stresses causeshrinkage,warpage,and a decrease in environmental stresscrack resistance.This practice estimates the relative magnitude1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.Current edition approved April 1,2012.Published May 2012.Originallyapproved in 2008.Last previous edition approved in 2008 as D7474-08.DOI:10.1520/D7474-12.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.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 States1 of residual stresses in parts produced from the series of sulfoneplastics(SP),namely polysulfone(PSU),polyethersulfone(PESU),and polyphenylsulfone(PPSU)materials.5.2 No direct correlation has been established between theresults of the determination of residual stresses by this practiceand part performance properties.For this reason,this practiceis not recommended as a substitute for other tests,nor is itintended for use in purchasing specifications for