ASTM_D_955_-_08_2014.pdf

Designation:D95508(Reapproved 2014)Standard Test Method ofMeasuring Shrinkage from Mold Dimensions ofThermoplastics1This standard is issued under the fixed designation D955;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method is intended to measure shrinkage frommold cavity to molded dimensions of thermoplastics whenmolded by compression or injection processes with specifiedprocess conditions.1.2 This test method covers shrinkage measurements at 24and 48 hours.1.3 This method will give comparable data based on stan-dard specimens and can not predict absolute values in actualmolded parts with varying flow paths,wall thicknesses,pres-sure and temperature gradients and process conditions.Differ-ences in mold shrinkage may also be observed among the threespecimen geometries described in this test method.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are given forinformation only.1.5 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.NOTE1This standard and ISO 294-3 are equivalent in the design ofspecimen D2.This test method is equivalent to ISO 294-4 where Type D2specimens and the procedure in Appendix X2 are used.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD788 Classification System for Poly(Methyl Methacrylate)(PMMA)Molding and Extrusion CompoundsD883 Terminology Relating to PlasticsD3641 Practice for Injection Molding Test Specimens ofThermoplastic Molding and Extrusion MaterialsD4066 Classification System for Nylon Injection and Extru-sion Materials(PA)D4549 Classification System and Basis for Specification forPolystyrene and Rubber-Modified Polystyrene Moldingand Extrusion Materials(PS)D4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens,Plaques,or SheetsD4976 Specification for Polyethylene Plastics Molding andExtrusion MaterialsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6778 Classification System and Basis for Specification forPolyoxymethylene Molding and Extrusion Materials(POM)D6779 Classification System for and Basis of Specificationfor Polyamide Molding and Extrusion Materials(PA)E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:3ISO 293 PlasticsCompression Moulding Test Specimensof Thermoplastic MaterialsISO 294-1 PlasticsInjection Moulding of Test Specimensof Thermoplastic MaterialsPart 1:General Principles,and Moulding of Multipurpose and Bar Test specimensISO 294-3 PlasticsInjection Moulding of Test Specimensof Thermoplastic MaterialsPart 3:Small PlatesISO294-4 PlasticsInjectionMouldingofTestSpecimensPart 4:Determination of Moulding Shrink-age3.Terminology3.1 DefinitionsGeneral definitions of terms applying tothis test method appear in Terminology D883.3.2 Definitions of Terms Specific to This Standard:1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved Aug.1,2014.Published August 2014.Originallyapproved in 1948.Last previous edition approved in 2008 as D955-08.DOI:10.1520/D0955-08R14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.1 jetting,nnon-uniform multi-directional flow frontapparent on the surface of the mold due to rapid filling of themold cavity.4.Summary of Test Method4.1 The principle of this test method is to compare moldcavity dimensions with specimen dimensions and report thedifferences in percent.5.Significance and Use5.1 Injection MoldingIn injection molding,the differencebetween the dimensions of a mold cavity and of the moldedspecimen may vary according to the design of the mold andoperation of the molding process.Factors such as mold andmelt temperature,fill times,and packing conditions are knownto affect shrinkage significantly.Adherence to the specifiedmold design(see 7.1)and specifications outlined in PracticeD3641 or ISO 294-4 or the appropriate m