ASTM F1921-12

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Designation:F1921–98(Reapproved2004) Designation:F1921–12
Standard Test Methods for
Hot Seal Strength (Hot Tack) of Thermoplastic Polymers and
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Blends Comprising the Sealing Surfaces of Flexible Webs
This standard is issued under the fixed designation F1921; the number immediately following the designation indicates the year of
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.
1. Scope
1.1 These two test methods cover laboratory measurement of the strength of heatseals formed between thermoplastic surfaces
of flexible webs, immediately after a seal has been made and before it cools to ambient temperature (hot tack strength).
1.2 These test methods are restricted to instrumented hot tack testing, requiring a testing machine that automatically heatseals
a specimen and immediately determines strength of the hot seal at a precisely measured time after conclusion of the sealing cycle.
An additional prerequisite is that the operator shall have no influence on the test after the sealing sequence has begun. These test
methods do not cover non-instrumented manual procedures employing springs, levers, pulleys and weights, where test results can
be influenced by operator technique.
1.3 Twovariationsoftheinstrumentedhottacktestaredescribedinthesetestmethods,differingprimarilyintworespects:((a))
rate of grip separation during testing of the sealed specimen, and ((b)) whether the testing machine generates the cooling curve
of the material under test, or instead makes a measurement of the maximum force observed following a set delay time. Both test
methods may be used to test all materials within the scope of these test methods and within the range and capacity of the machine
employed. They are described in Section 4.
1.4SI units are preferred and shall be used in referee decisions.
1.4 SI units are preferred and shall be used in referee decisions. Values stated herein in inch-pound units are to be regarded
separately and may not be exact equivalents to SI units. Therefore, each system shall be used independently of the other.
Combining values from the two systems may result in non-conformance with the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. The operator of the equipment is to be aware of pinch points as the seal jaws come together to make a
seal, hot surfaces of the jaws, and sharp instruments used to cut specimens. It is recommended that the operator review safety
precautions from the equipment supplier.
2. Referenced Documents
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2.1 ASTM Standards:
D882 Test Method for Tensile Properties of Thin Plastic Sheeting
E171 Practice for Conditioning and Testing Flexible Barrier Packaging Practice for Conditioning and Testing Flexible Barrier
Packaging
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
F88 Test Method for Seal Strength of Flexible Barrier Materials
F2029 Practices for Making Heatseals for Determination of Heatsealability of Flexible Webs as Measured by Seal Strength
3. Terminology
3.1 Definitions:
3.1.1 adhesive failure, n—a failure mode in which the seal fails at the original interface between the surfaces being sealed.
3.1.2 breadth, n—temperature range over which peel force of a seal is (relatively) constant.
3.1.3 burnthrough, n—a state or condition of a heatseal characterized by melted holes and thermal distortion.
3.1.2.1
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These test methods are under the jurisdiction ofASTM Committee F02 on Flexible Barrier MaterialsPackaging and are the direct responsibility of subcommittee F02.20
on Physical Properties.
Current edition approved Oct. 10, 1998. Published February 1999. DOI: 10.1520/F1921-98R04.
Current edition approved July 1, 2012. Published August 2012. Originally approved in 1998. Last previous edition approved in 2004 as F1921-98(2004). DOI:
10.1520/F1921-12.
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