ASTM_F_1921_-_F_1921M_-_12e1.pdf

Designation:F1921/F1921M121Standard Test Methods forHot Seal Strength(Hot Tack)of Thermoplastic Polymers andBlends Comprising the Sealing Surfaces of Flexible Webs1This standard is issued under the fixed designation F1921/F1921M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEDesignation was corrected editorially in October 2013.1.Scope1.1 These two test methods cover laboratory measurementof the strength of heatseals formed between thermoplasticsurfaces of flexible webs,immediately after a seal has beenmade and before it cools to ambient temperature(hot tackstrength).1.2 These test methods are restricted to instrumented hottack testing,requiring a testing machine that automaticallyheatseals a specimen and immediately determines strength ofthe hot seal at a precisely measured time after conclusion of thesealing cycle.An additional prerequisite is that the operatorshall have no influence on the test after the sealing sequencehas begun.These test methods do not cover non-instrumentedmanual procedures employing springs,levers,pulleys andweights,where test results can be influenced by operatortechnique.1.3 Two variations of the instrumented hot tack test aredescribed in these test methods,differing primarily in tworespects:(a)rate of grip separation during testing of the sealedspecimen,and(b)whether the testing machine generates thecooling curve of the material under test,or instead makes ameasurement of the maximum force observed following a setdelay time.Both test methods may be used to test all materialswithin the scope of these test methods and within the range andcapacity of the machine employed.They are described inSection 4.1.4 SI units are preferred and shall be used in refereedecisions.Values stated herein in inch-pound units are to beregarded separately and may not be exact equivalents to SIunits.Therefore,each system shall be used independently ofthe other.Combining values from the two systems may resultin non-conformance with the standard.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.The operator of theequipment is to be aware of pinch points as the seal jaws cometogether to make a seal,hot surfaces of the jaws,and sharpinstruments used to cut specimens.It is recommended that theoperator review safety precautions from the equipment sup-plier.2.Referenced Documents2.1 ASTM Standards:2D882 Test Method for Tensile Properties of Thin PlasticSheetingE171 Practice for Conditioning and Testing Flexible BarrierPackagingE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodF88 Test Method for Seal Strength of Flexible BarrierMaterialsF2029 Practices for Making Heatseals for Determination ofHeatsealability of Flexible Webs as Measured by SealStrength3.Terminology3.1 Definitions:3.1.1 adhesive failure,na failure mode in which the sealfails at the original interface between the surfaces being sealed.3.1.2 breadth,ntemperature range over which peel forceof a seal is(relatively)constant.3.1.3 burnthrough,na state or condition of a heatsealcharacterized by melted holes and thermal distortion.3.1.3.1 DiscussionBurnthrough indicates that the sealingconditions(time or temperature,or both)were too high toproduce an acceptable seal.1These test methods are under the jurisdiction of ASTM Committee F02 onFlexible Barrier Packaging and are the direct responsibility of subcommittee F02.20on Physical Properties.Current edition approved July 1,2012.Published August 2012.Originallyapproved in 1998.Last previous edition approved in 2004 as F1921-98(2004).DOI:10.1520/F1921-12E01.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.4 cohesive failure,na failure mode where either orboth of the sealed webs fails by splitting approximately parallelto the seal,and the seal itself remains intact.3.1.4.1 DiscussionRefer to Fig.1.The term may bedefined somewhat differently when applied to sealing systemsinvolving an adhesive material as a separate component.3.1.5 cooling curve,nthe graphical depiction of the in-crease in strength of the seal with time,as it cools during theperiod immediately following conclusion of the sealing cycle(for example,see Fig.2).3.1.5.1 DiscussionThe cooling curve is a plot of hot sealstrength versus c