1、Designation: F2029 16Standard Practices forMaking Laboratory Heat Seals for Determination of HeatSealability of Flexible Barrier Materials as Measured by SealStrength1This standard is issued under the fixed designation F2029; the number immediately following the designation indicates the year oforig
2、inal 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. Scope1.1 These practices cover laboratory preparation of heatseals. Thes
3、e practices also cover the treatment and evaluationof heat seal strength data for the purpose of determining heatsealability of flexible barrier materials. It does not cover therequired validation procedures for the production equipment.1.2 Testing of seal strength or other properties of the heatsea
4、ls formed by these practices is not included in this standard.Refer to Test Method F88 for testing heat seal strength. Thispractice does not apply to hot tack testing, which is covered inF1921.1.3 The practices of this standard are restricted to preparingheat seals using a sealer employing hot-bar o
5、r impulse sealingmethods, or both.1.4 This practice is intended to assist in establishing startingrelationships for sealing flexible barrier materials. Additionalguidance may be needed on how to set up sealing conditionsfor flexible barrier materials on commercial/production sealingequipment.1.5 Sea
6、ls may be made between webs of the same ordissimilar materials. The individual webs may be homoge-neous in structure or multilayered (coextruded, coated,laminated, and so forth).1.6 Strength of the heat seal as measured by Test MethodF88 is the sole criterion for assessing heat sealability employedi
7、n these practices.1.7 Other aspects of heat sealability, such as seal continuity,typically measured by air-leak, dye penetration, visualexamination, microorganism penetration, or other techniques,are not covered by these practices.1.8 The values stated in SI units are to be regarded asstandard. The
8、values given in parentheses are for informationonly.1.9 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
9、 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F88 Test Method for Seal Strength of Flexible BarrierMaterialsF1921 Test Methods for Hot Seal Strength (Hot Tack) ofThermoplastic Polymers and Blends Comprising the Seal-ing Surfaces of Flexible WebsD4332 Practice for Co
10、nditioning Containers, Packages, orPackaging Components for Testing3. Terminology3.1 Definitions:3.1.1 dwell time, nthe time interval when the sealing jawsare in contact with, and exerting pressure on, the material beingsealed.3.1.2 heat seal curve, na plot of measured seal strength asa function of
11、sealing temperature at a fixed dwell time andsealing pressure.3.1.3 heat seal strength, nforce per unit width of sealrequired to progressively separate a flexible material from arigid material or another flexible material, under the conditionsof the test. Also known as seal strength.3.1.4 heat seala
12、bility, nthe ability of thermoplastic poly-mers and blends, when comprising a sealing surface of aflexible web, that defines how well the material bonds to itselfor a dissimilar material upon the application of pressure, heat,and dwell (time), as judged by the heat seal curve.3.1.4.1 DiscussionSince
13、 heat seal strength can be mea-sured either while the seal is still hot (hot tack) or after cooling1These practices are under the jurisdiction of ASTM Committee F02 on PrimaryBarrier Packaging and are the direct responsibility of Subcommittee F02.20 onPhysical Properties.Current edition approved Nov
14、. 15, 2016. Published November 2016. Originallyapproved in 2000. Last previous edition approved in 2008 as F2029 08. DOI:10.1520/F2029-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
15、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 States1and stabilizing (ultimate seal strength), a complete evaluationof heat sealability of a material may include
16、both tests.3.1.5 hot tack, na measure of the seal strength of a hot sealmeasured at a specified time interval after completion of thesealing cycle but prior to the temperature of the seal reachingambient. Refer to Test Methods F1921.3.1.6 seal initiation temperature, non a heat seal curve,the sealin
17、g temperature/dwell pressure at which heat sealstrength first begins to trend upward from zero heat sealstrength.3.1.7 sealing interface, nthe interface of the two websurfaces being sealed.3.1.8 sealing pressure, nthe force per unit area of sealapplied to the material by the sealing jaws during the
18、sealingprocess.3.1.9 sealing temperature, nthe set point of eachtemperature-controlled sealing jaw. The set point temperatureis the controller setting which will produce the desired surfacetemperature. Often, the set point temperature will be higherthan the surface temperature.3.1.10 ultimate seal s
19、trength, nthe final value of strengththat is reached after the heat seal has both cooled to ambienttemperature and achieved stability in strength.3.1.10.1 DiscussionSome materials, when cooling from amelt, continue to change in strength over extended periods oftime after reaching ambient temperature
20、.4. Significance and Use4.1 This practice facilitates the determination of laboratoryheat sealability of flexible barrier materials. While it is neces-sary to have a heat seal layer that provides adequate sealstrength for the application, other material properties, such asthe overall construction an
21、d thickness, will impact the sealingproperties of the material. This practice allows the impact ofchanges in material properties on heat sealability to be mea-sured.4.2 Due to differences between a laboratory sealer andmanufacturing equipment (for example, scale, size of sealingarea, and processing
22、speed), there may be a significant differ-ence between the capability and output of a laboratory heatsealer and that of manufacturing equipment. Hence, care mustbe taken when applying a heat seal curve study as outlined inthese practices to manufacturing equipment. The heat sealcurve and the corresp
23、onding seal strength data are intended toprovide a starting point for determination of sealing conditionsfor full scale manufacturing equipment.5. Apparatus5.1 Continuous Heat Bar Sealer:5.1.1 Sealing JawsTemperature-controlled jaw or jawswith appropriate sealing surfaces to provide a flat seal. If
24、onlyone heated jaw is used, the unheated jaw should be coveredwith a gasket material such as a silicone rubber (to prevent thetest specimen from adhering to the sealing jaws) of knowndurometer and, optionally, an anti-stick coating or covering.5.1.1.1 Jaw Temperature ControlEach temperature-controll
25、ed jaw should have independent temperature controland the precision of the controlling unit should be known andcalibrated. The temperature should be verified periodicallyusing a calibrated pyrometer adequate for the range of use.5.1.1.2 Jaw Coatings or CoveringsFor the heated jaw(s),anti-stick or co
26、mpressible jaw coatings or coverings, such assilicone rubber, TFE-fluorocarbon, TFE-fluorocarbon/glasscloth, or oriented PET film are often used to prevent the testspecimen from adhering to the sealing jaws. For an unheatedjaw, silicone or other heat-resistant rubbers of known durom-eter may be used
27、. The rubber may be covered with TFE-fluorocarbon, TFE-fluorocarbon/glass cloth, or oriented PETfilm.NOTE 1Thick or heat flow-resistant materials will impact the rate ofheat transfer from jaws to sealing surface. It is important to inspect thequality of these materials periodically to prevent loss o
28、f properties thatmay cause unwanted temperature fluctuations in the sealing process.5.1.1.3 Jaw Sealing SurfacesIdeally, the jaw sealing sur-faces should be parallel when actuated and can be aligned, ifneeded. The uniformity of pressure across the sealing jawsshould be checked. This may be done usin
29、g pressure-indicatingmaterials or devices by actuating the sealing jaws while atambient temperature or at elevated temperatures, as appropri-ate.5.1.2 Dwell TimeVariable control and readout of dwelltime. A range of 0.1 to 10 seconds is desirable. The precisionof the dwell time control unit should be
30、 known and calibrated.NOTE 2Jaw closure time and set dwell time may be differentdepending on heat sealer equipment.5.1.3 PressureVariable control, via a pressure gage orload cell, with readout of the air supply pressure or the sealingpressure, respectively.5.1.3.1 The applied sealing pressure for ma
31、chines that haveonly an air pressure gauge on the air supply line and whosecylinder size is known should be calculated (neglecting anylosses due to mechanical work). The following formula may beused for this calculation.Pactual5SAcylAcontactDPline(1)where:Pactual= actual or applied pressure of the s
32、ealing jaw,Pline= pressure of the incoming air line,Acontact= area of the sealing jaw in contact with material,andAcyl= sum of the cross-sectional areas of all cylinders.5.1.3.2 When materials are being sealed under pressure andsilicone rubber is used on one or both of the jaws, the siliconerubber w
33、ill compress. When thin materials being sealed arenarrower than the full length of the sealing jaw, the compres-sion can be significant enough to change the contact to the fullarea of the jaw. As a result, the pressure is then distributedacross the entire surface and this area is what should be used
34、 inthe pressure calculation. When sealing thick materials, only thearea of the seal should be used to calculate the sealing pressuresince contact is limited to the surface of the thicker materials.5.2 Impulse Sealer5.2.1 Impulse Sealing JawsImpulse sealing jaw or jawswith an impulse band applied to
35、it and with appropriate sealingF2029 162surfaces to provide a flat seal. If only one impulse sealing jawis used, the other jaw should be covered with a gasket materialsuch as a silicone rubber (to prevent the test specimen fromadhering to the sealing jaws) of known durometer and,optionally, an anti-
36、stick coating or covering.5.2.1.1 Impulse Sealing Jaw Temperature ControlEachimpulse jaw with an impulse band applied to it should haveindependent and calibrated controls. The location and precisionof the controlling unit (such as a thermocouple or calibratedheater band) should be known. The output
37、temperature shouldbe verified periodically.NOTE 3Some impulse sealers also include a “cooling” cycle to ensurethat the seal is undisturbed mechanically after the seal is formed andbefore the jaws open.5.2.1.2 Jaw Coatings or CoveringsEach impulse jaw withan impulse band applied to it may be covered
38、with an anti-stickcovering, such as TFE-fluorocarbon or TFE-fluorocarbon/glasscloth, to prevent the test specimen from adhering to the sealingjaws. For an unheated jaw, silicone or other heat resistantrubbers of known durometer may be used. The rubber may becovered with TFE-fluorocarbon, TFE-fluoroc
39、arbon/glass cloth.NOTE 4Thick or heat flow-resistant materials will impact the rate ofheat transfer from jaws to sealing surface. It is important to inspect thequality of these materials periodically to prevent loss of properties thatmay cause unwanted temperature fluctuations in the sealing process
40、.5.2.1.3 Jaw Sealing SurfacesIdeally, the jaw sealing sur-faces should be parallel, and can be aligned if needed. Theuniformity of pressure across the sealing jaws should bechecked. This may be done using pressure-indicating materialsor devices by actuating the sealing jaws while at ambienttemperatu
41、re or at elevated temperatures, as appropriate.5.2.2 Dwell TimeVariable control and readout of heatingdwell time, and cooling dwell time, if appropriate. A range of0.1 to 10 seconds is desirable. The precision of the dwell timecontrol unit(s) should be known and calibrated.NOTE 5Jaw closure time and
42、 heating dwell time may be differentdepending on impulse sealer equipment.5.2.3 PressureVariable control, via a pressure gage orload cell, with readout of the air supply pressure or the sealingpressure, respectively.5.2.3.1 The applied sealing pressure for machines that haveonly an air pressure gaug
43、e on the air supply line and whosecylinder size is known should be calculated. Eq 1 can be usedfor this calculation. If jaw closure is through a cantileveredmechanism, consult with your equipment manufacturer orsupplier to determine applied pressure.5.2.3.2 When materials are being sealed under pres
44、sure andsilicone rubber is used on one or both of the jaws, the siliconerubber will compress. When thin materials being sealed arenarrower than the full length of the sealing jaw, the compres-sion can be significant enough to change the contact to the fullarea of the jaw. As a result, the pressure i
45、s then distributedacross the entire surface and this area is what should be used inthe pressure calculation. When sealing thick materials, only thearea of the seal should be used to calculate the sealing pressuresince contact is limited to the surface of the thicker materials.6. Test Specimen6.1 The
46、 number of test specimens shall be chosen to permitan adequate determination of representative performance basedon an appropriate rationale. When heat seal strength will bemeasured at a series of sealing temperatures, an adequate oragreed upon number of replicates shall be used to determinethe mean
47、value for each material at each temperature. When themeasurements will not be part of a series where an identifiabletrend is expected, a separate determination of the number ofreplicates should be made.6.2 Mark the machine or transverse direction (if known andrelevant to the test outcome) and the se
48、al side of each sampleto be evaluated. Superimpose the two pieces to be sealed, withthe transverse directions parallel and the seal surfaces facingeach other. Seal each specimen with the jaws parallel to eitherthe machine or transverse direction noting the orientation of thesample. To minimize varia
49、bility, perform the heat seal processat the same location relative to the sealing jaws. One or morestrips for seal-strength testing will subsequently be cut perpen-dicular to the seal where the sealing temperature profile isknown to be consistent (commonly near the center of the sealedstrip). The seal(s) may then be peeled by pulling the stripaccording to Test Method F88.NOTE 6The seal must be located on the specimen such that the legsof the strip on each side of the seal will be long enough to span thedistance between the grips of the testing machine.6
