1、Designation: F 2029 00Standard Practices forMaking Heatseals for Determination of Heatsealability ofFlexible Webs as Measured by Seal Strength1This standard is issued under the fixed designation F 2029; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These practices cover laboratory preparation of heat-seals and the treatment and eval
3、uation of heatseal strength datafor the purpose of determining heatsealability of flexiblebarrier materials.1.2 Testing strength or other properties of the heatsealsformed by these practices is not included in this standard. Referto Test Methods F88for testing heatseal strength.1.3 The practices of
4、this standard are restricted to sealingwith a machine employing hot-bar jaws. Impulse, high-frequency, and ultrasonic heating methods are not included.1.4 These practices apply primarily to webs intended to beused on commercial machines employing reciprocating sealingjaws, such as most vertical form
5、-fill packaging machines,platen heatsealers, etc. Conditions of dwell time and sealingpressure on machines of this type typically are different fromthose on rotary machines by an order of magnitude or more.1.5 The procedures of these practices with respect to choiceof heatsealing conditions apply eq
6、ually whether the applicationis to ultimate seal strength or hot tack measurement.1.6 Seals may be made between webs of the same ordissimilar materials. The individual webs may be homoge-neous in structure or multilayered (coextruded, coated, lami-nated, etc.).1.7 Strength of the heatseal is the cri
7、terion for judgingheatsealability employed in these practices.1.8 Determination of heatsealability as judged by seal con-tinuity, typically measured by air-leak, dye penetration, visualexamination, microorganism penetration or other techniques,are not covered by these practices.1.9 Two variations of
8、 the heatsealing procedure are de-scribed herein, differing in whether the objective of the testingis to determine, the heatsealability of the surface, or how wellthe entire web would heatseal in applications where the sealinginterface may not reach jaw temperature.1.9.1 Practice A, Heatsealability
9、of a SurfaceThismethod measures sealability of the web surface, or sealantlayer if there is one, as a function of interface temperature,which is independent of the influence of other web character-istics, such as total thickness and construction.1.9.2 Practice B, Web Sealability at Short Dwell TimeT
10、hetest seal is made at a dwell time shorter than required for thesealing interface to reach the jaw temperature level, simulatingconditions on high-speed vertical form-fill machines, or onslower machines where the condition of nonequilibrium alsoexists. The resulting heatseal strength, under nonequi
11、libriumconditions, is then dependent not only on characteristics of thewebs sealing surface, but also on web thickness, construction,and other factors affecting rate of heat transfer from jaws to thesealing interface. These include machine factors; (for example,anti-stick jaw treatments, etc).1.10 T
12、his 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 Docume
13、nts2.1 ASTM Standards:2F88 Test Method for Seal Strength of Flexible BarrierMaterialsF 1921 Test Methods for Hot Seal Strength (Hot Tack) ofThermoplastic Polymers and Blends Comprising the SealingSurfaces of Flexible Webs3. Terminology3.1 Definitions:3.1.1 dwell time, nthe time interval when the sea
14、ling jawsare in contact with, and exerting pressure on, the material beingsealed.3.1.2 equilibrium dwell time, nany dwell time in excess ofthat required for the seal strength to reach its maximum levelfor the jaw temperature employed.3.1.2.1 DiscussionApplies only when both jaws are atequal temperat
15、ure (see Annex A1.3).3.1.3 heatseal curve, na plot of apparent seal strengthversus sealing temperature.1These practices are under the jurisdiction ofASTM Committee F02 on FlexibleBarrier Materials and are the direct responsibility of Subcommittee F02.20 onPhysical Properties.Current edition approved
16、 May 10, 2000. Published July 2000.2For 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.1Copyright ASTM Internatio
17、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3.1 DiscussionThis is the basic curve for comparingsealability of materials. It plots the force required to extend asealed test strip to failure, as a function of sealing temperature.The portion of the curve
18、 at higher sealing temperatures may beaffected by failure of the substrate and may not be an accuraterepresentation of seal strength.3.1.4 heatseal strength, nforce required to peel the sealapart, per unit width of seal.3.1.4.1 DiscussionIn many tests of seal strength it is notthe seal that fails, i
19、t is the substrate. In those tests, the trueheatseal strength may be somewhat higher than the measuredforce that caused the specimen to fail. Homogeneous materialswith fusion seals, for example, commonly break along a lineimmediately adjacent to the seal, while the seal itself remainsintact (see Tes
20、t Methods F88).3.1.5 heatsealability, nthe property of thermoplastic poly-mers and blends, when comprising a surface of a flexible web,that defines how well the material heatseals.3.1.5.1 DiscussionHow well the material heatseals isexpressed quantitatively as seal strength as a function of thesealin
21、g conditions of temperature, time, and pressure. Sincestrength of a heatseal can be measured either while the seal isstill hot (hot tack) or after cooling and stabilizing (ultimatestrength), a complete evaluation of heatsealability of a materialmust include both tests.3.1.6 hot tack, nstrength of a
22、hot seal measured at aspecified time interval after completion of the sealing cycle butprior to the temperature of the seal reaching ambient. Refer toTest Methods F 1921.3.1.7 seal initiation temperature, nthe sealing tempera-ture at which a heatseal of significant strength (0.5 N/cm; 125g/25 mm; 0.
23、3 lb/in.) is produced.3.1.8 sealing interface, nthe interface between two websurfaces being sealed.3.1.9 sealing pressure, nthe force per unit area of sealapplied to the material during the sealing process.3.1.9.1 DiscussionDuring the dwell time, the sealingpressure pulse rises from zero usually to
24、a plateau level andthen drops to zero. Frequently, there is an initial spike. Veryshort dwell times may not have a plateau. Sealing pressure iscompletely described by the curve of pressure versus time, buttwo parameters from the curve commonly are used instead tocharacterize the pressure variable. O
25、ne is a calculated averagepressure, that excludes the initial rise, as well as, the terminalfall of pressure, and the other is the maximum value reachedeither during any initial impact spike or later.NOTE 1A common error is to report air pressure in the cylinderapplying the force as the sealing pres
26、sure.3.1.10 sealing temperature, nmaximum temperaturereached at the sealing interface during the dwell time of asealing cycle.3.1.10.1 DiscussionSealing temperature will equal jawtemperature (both jaws at same temperature) if the dwell timeis long enough for the interface to reach temperature equili
27、b-rium with the jaws. This point has been reached when sealstrength no longer rises with increasing dwell time.3.1.11 ultimate seal strength, nthe final value of strengththat is reached after the heatseal has both cooled to ambienttemperature and achieved stability in strength.3.1.11.1 DiscussionSom
28、e materials, when cooling from amelt, continue to change in strength over extended periods oftime after reaching ambient temperature.4. Significance and Use4.1 Practice A, Surface HeatsealabilityThis practice leadsto determining the heatsealability of a surface, or sealant layerif there is one, as a
29、 function of interface temperature, free of theinfluence of other web properties. Commercially, its applica-tions are in development of improved polymers and blends tobe used as the sealant layer in coextruded films and laminatedand coated web constructions.Also it is the appropriate methodfor quali
30、ty control in manufacture of those films and lamina-tions, since a QC test should be affected by the property beingtested for, for example, heatsealability of the surface, and, sofar as possible, not by other properties of the web, for example,total thickness, that are measured independently by othe
31、rmethods.NOTE 2Sealant-layer thickness may affect surface heatsealability.4.2 Practice B, Web SealabilityWhile it is necessary tohave a heatseal surface layer that has adequate seal strength forthe application, the web also will have a specific constructionand total thickness, both chosen to satisfy
32、 requirements otherthan heatsealability. Practice B compares specific web con-structions for their suitability for applications where the dwelltime may be too short for the sealing interface to reach jawtemperature. With this test method, both web construction andthickness, in addition to properties
33、 of the sealant layer, affectsealing performance. If the rate of heat transfer through theweb due to its construction or total thickness is too slow for theproduction rate required, it may be necessary to use a sealantlayer with a lower seal-inception temperature or fusion tem-perature.5. Apparatus5
34、.1 Heatsealer:5.1.1 Sealing JawsTwo-heated jaws with flat sealingsurfaces. Two-heated jaws are required to conduct Practice A.Practice B may be used with one-heated jaw only when theapplication is to commercial sealers with like configuration.5.1.1.1 Jaw Temperature ControlEach jaw must haveindepend
35、ent temperature control. The recommended minimumprecision of control is 6 1C.5.1.1.2 Jaw Coatings or CoveringsAnti-stick or com-pressible jaw coatings or coverings, such as TFE-fluorocarbon,TFE-fluorocarbon/glass cloth, silicone rubber or other heat-resistant rubbers, polyester film, etc., are admis
36、sible, althoughtest conditions may require adjustment in some cases.5.1.1.3 Jaw Sealing Surfaces, must be capable of beingaligned for parallelism.5.1.1.4 Capability for Quick Jaw Change to serrated orother jaw styles is desirable to increase the machines range ofsimulation testing.5.1.2 Dwell TimeVa
37、riable control and readout of dwelltime, with minimum range of 100 to 10 000 ms.F20290025.1.2.1 Time of jaw closure should be measured directly (asby force sensor output, micro switch, optically, etc.), andcontrolled therefrom.5.1.2.2 Precision of dwell time control should be 6 10 msor better.5.1.3
38、Pressure, variable control, with readout of sealingpressure.5.1.3.1 Machines, that have only an air pressure gage fromwhich sealing pressure must be calculated, should be providedwith nomographs from which sealing pressure can be readdirectly from air pressure measurements.6. Test Specimen6.1 The nu
39、mber of test specimens shall be chosen to permitan adequate determination of representative performance.When heatseal strength will be measured at a series of sealingtemperatures, a minimum of three replicates shall be used todetermine the mean value for each material at each tempera-ture. When the
40、measurements will not be part of a series wherean identifiable trend is expected, a minimum of five replicatesshall be employed.6.2 In planning the number of specimens required, note thatonly one strength test should be made from each heatseal.6.3 Specimens for heatsealing can be prepared by cutting
41、the test material into pieces 15 by 15 cm 6 by 6 in. Mark thetransverse direction and the seal side of each piece. Superim-pose the two pieces to be sealed, with the transverse directionsparallel and the seal surfaces facing each other. If a group ofspecimens is to be prepared prior to sealing, it i
42、s convenient tostaple the pairs, with caution to avoid staples in the areas to besealed and from which the test strip will be cut subsequently.Seal the specimens with the jaws parallel to the transversedirection. A strip for seal-strength testing will subsequently becut perpendicular to the seal at
43、its center, and the seal will bepeeled by pulling the strip in the machine direction of the web.NOTE 3The seal must be located on the specimen so the legs of thestrip on each side of the seal will be long enough to span the distancebetween the grips of the testing machine.6.4 Alternatively to sealin
44、g a wide specimen and thencutting a strip for strength testing, strips of the width forstrength testing may be cut in the machine direction and sealed,either to strips of similar material or to dissimilar strips. Thesealed strip may then be tested for strength without furtherpreparation. This altern
45、ative is mandatory for hot-tack testing.Comparisons should be made only among specimens sealed bythe same procedure.6.4.1 When using sealing machines that automatically loadand seal a specimen strip without operator intervention, sealingof dissimilar materials is accomplished by preparing a speci-me
46、n strip that is a composite of the two materials to be sealed,taped together at the center. Refer to the machine manufactur-ers recommendations for details appropriate to the machineused.NOTE 4Caution: Be sure to adjust the seal area factor in calculatingsealing pressure when switching from a wide s
47、eal to a strip seal.6.4.2 Common strip widths are 25 mm (1.00 in.) and 15 mm(0.59 in.).6.5 If the material is anisotropic and the data are expected toapply to situations where the seal may be stressed transversely,specimens cut perpendicular to those described in 6.3 also shallbe taken.7. Procedure7
48、.1 Calibration and AlignmentPrior to starting testing,insure that the heatsealer is in proper calibration and that thejaws have been aligned for parallelism.7.2 Sealing Conditions, for heatsealability testing, eitherultimate seal strength or hot tack, shall be within the rangesspecified below for al
49、l makes and types of heatsealers.7.2.1 Practice A, Surface Sealability: Heatsealability of theweb surface as a function of interface temperature.7.2.1.1 TemperatureBoth jaws shall be set at the sametemperature.7.2.1.2 Dwell TimeThe dwell time must be long enoughfor the sealing interface to come to the known temperature ofthe jaws. This depends on the thickness and construction of theweb, as well as on jaw configuration factors. Typical minimumdwell times (without anti-stick jaw covering):Films: 1 mil (25) and under: dwell time, 500 ms (.5 s).Film
