ASTM_D_2838_-_09e1.pdf

Designation:D2838091Standard Test Method forShrink Tension and Orientation Release Stress of PlasticFilm and Thin Sheeting1This standard is issued under the fixed designation D2838;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.1NOTEEditorially corrected Note 1 in August 2015.1.Scope*1.1 This test method covers the determination of the shrinktension and related characteristics,that is,shrink force andorientation release stress,of heat-shrinkable plastic film andsheeting of less than 1.0 mm(0.04 in.)thickness.Twoprocedures are described that permit the measurement of shrinkforces at predetermined temperatures.They are as follows:1.1.1 Procedure A is designed to measure the maximumforce exerted by a specimen that is totally restrained fromshrinking as it is heated rapidly to a specific temperature.1.1.2 Procedure B is designed to measure the maximumforce exerted by a specimen that is permitted to shrink apredetermined amount prior to restraint while being heatedrapidly to a specific temperature.1.2 Orientation release stress can be determined from thedata obtained using Procedure A.1.3 The values stated in SI units are to be regarded as thestandard.The values in parentheses are for information only.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.NOTE1Film has been arbitrarily defined as sheeting having nominalthickness not greater than 0.25 mm(0.010 in.).NOTE2There is no known ISO equivalent to this test method.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD4000 Classification System for Specifying Plastic Materi-alsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6287 Practice for Cutting Film and Sheeting Test Speci-mensD6988 Guide for Determination of Thickness of Plastic FilmTest SpecimensE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 orientation release stress,nthe maximum shrinktension developed by a film in a specified direction throughoutits range of shrink temperatures while totally restrained fromshrinking.3.1.2 shrink force,nthe force per original unit widthdeveloped by a film in a specified direction and at a specifiedtemperature in its attempt to shrink while under restraint.3.1.3 shrink tension,nthe force per original averagecross-sectional area developed by a film in a specified directionand at a specified temperature in its attempt to shrink whileunder restraint.3.2 Definitions:3.2.1 For definitions of terms used in this test method,referto Terminology D883.4.Summary of Test Method4.1 A 25.4-mm(1-in.)wide strip of film or sheeting isclamped in the arms of a shrink tension holder(see Fig.1),onearm of which contains a strain gage.The holder is immersed ina hot bath and the force exerted by the film is measured by thestrain gage.The data is collected by a data acquisition device.The tests may be carried out with or without free shrinkage ofthe material before restraint.5.Significance and Use5.1 As a result of the manufacturing process,internalstresses are locked into the film and these can be released by1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film,Sheeting,andMolded Products.Current edition approved May 1,2009.Published June 2009.Originallyapproved in 1969.Last previous edition approved in 2008 as D2838-08.DOI:10.1520/D2838-09.2For 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.*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 heating.For any given type of film or sheeting,the tempera-tures at which shrinkage will begin are related to processingtechniques employed to manufacture the film and also may berelated to a phase transition in the base resin.5.2 Shrink tension affects the appearance and performanceof a film in a shrink-packaging application.It may also be usedto determine the degree and direction of orientation.Theorientation exerts a great influence upon important physicalcharacteristics such as tensile strength,stiffness,tearresistance,and impact strength.5.3 Data from Procedure A are most useful for dete