ASTM_D_4703_-_16.pdf

Designation:D470316Standard Practice forCompression Molding Thermoplastic Materials into TestSpecimens,Plaques,or Sheets1This standard is issued under the fixed designation D4703;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 compression molding of ther-moplastic granules and milled stock for the preparation of testspecimens.21.2 While conditions for certain materials are given,theprimary source of specific conditions shall be the materialspecification standards for each type of material.1.3 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.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.NOTE1The main body of this practice is equivalent to ISO 293-1986.Annex A1 and ISO 293-1986 differ in some details;however,specimensprepared using Annex A1,Procedure A should be equivalent to thoseprepared using ISO 293-1986,Cooling Method D.Specimens preparedusing Annex A1,Procedure C should be equivalent to those preparedusing ISO 293-1986,Cooling Method B.However,due to the greatercooling rate tolerances of the ISO standard,specimens prepared inaccordance with ISO Cooling Method B may not be equivalent to AnnexA1,Procedure C.2.Referenced Documents2.1 ASTM Standards:3D618 Practice for Conditioning Plastics for TestingD1248 Specification for Polyethylene Plastics ExtrusionMaterials for Wire and CableD3350 Specification for Polyethylene Plastics Pipe and Fit-tings MaterialsD4976 Specification for Polyethylene Plastics Molding andExtrusion Materials2.2 ISO Standard:ISO 293 PlasticsCompression Moulding Test Specimensof Thermoplastic Materials43.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 average cooling rate(C/min),nthe cooling ratecalculated by dividing the difference between the molding anddemolding temperatures by the time required to cool the moldto the demolding temperature.3.1.2 cooling rate(C/h),nthe rate of cooling obtained bycontrolling the flow of the cooling fluid in such a way thatduring each 10-min interval,the deviation from this specifiedcooling rate shall not exceed the specified tolerance.3.1.3 demolding temperature,nthe temperature of themold or the press platens at the end of the cooling time,measured in the nearest vicinity to the molded material.3.1.3.1 DiscussionFor positive molds,holes are normallydrilled in the mold for measuring the temperatures defined in3.1.3 and 3.1.4.3.1.4 molding temperature,nthe temperature of the moldor the press platens during the preheating and molding time,measured in the nearest vicinity to the molded material.3.1.5 molding time,nthe time during which full pressureis applied while maintaining the molding temperature.3.1.6 picture frame mold,na flat piece of metal,usually ofbrass or steel,that has a center portion removed to provide thespecified shape and dimensions of the final molding.Thethickness of the metal is dependent on the desired thickness ofthe finished molding,taking into consideration the shrinkage ofthe material to be molded.The picture frame mold is some-times referred to as a chase.3.1.7 preheating time,nthe time required to heat thematerial in the mold up to the molding temperature whilemaintaining the contact pressure.1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved April 1,2016.Published April 2016.Originallyapproved in 1991.Last previous edition approved in 2010 as D4703 10a.DOI:10.1520/D4703-16.2This practice was created as a coalescence of and replacement for PracticesD1928,D2292,D3010,and D3463.3For 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.4ISO/IEC Selected Standards for Testing Plastics,available from ASTM.Alsoavailable from American National Standards Institute(ANSI),25 W.43rd St.,4thFloor,New York,NY 10036.*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 4.Significance and Use4.1 The methods by which sample materials are preparedand molded influence the mechanical properties of the speci-men.Unlike injection molding,the objective of compressionmolding is to produce test specimens or sheets that are bothhomogeneo