ASTM F1921-98(2004)
(Test Method)Standard Test Method for Hot Seal Strength (Hot Tack) of Thermoplastic Polymers and Blends Comprising the Sealing Surfaces of Flexible Webs
Standard Test Method for Hot Seal Strength (Hot Tack) of Thermoplastic Polymers and Blends Comprising the Sealing Surfaces of Flexible Webs
SIGNIFICANCE AND USE
In form-fill operations, sealed areas of packages are frequently subject to disruptive forces while still hot. If the hot seals have inadequate resistance to these forces, breakage can occur during the packaging process. These test methods measure hot seal strength and can be used to characterize and rank materials in their ability to perform in commercial applications where this quality is critical.
SCOPE
1.1 These 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.
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 Two variations of the instrumented hot tack test are described in these test methods, differing primarily in two respects: (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.
1.4 SI units are preferred and shall be used in referee decisions.
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.
General Information
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Standards Content (Sample)
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Designation:F1921–98(Reapproved2004)
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 2. Referenced Documents
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1.1 Thesetestmethodscoverlaboratorymeasurementofthe 2.1 ASTM Standards:
strength of heatseals formed between thermoplastic surfaces of D882 Test Method for Tensile Properties of Thin Plastic
flexible webs, immediately after a seal has been made and Sheeting
before it cools to ambient temperature. E171 Specification for Atmospheres for Conditioning and
1.2 These test methods are restricted to instrumented hot Testing Flexible Barrier Materials
tack testing, requiring a testing machine that automatically
3. Terminology
heatseals a specimen and immediately determines strength of
3.1 Definitions:
thehotsealatapreciselymeasuredtimeafterconclusionofthe
sealing cycle. An additional prerequisite is that the operator 3.1.1 adhesive failure, n—a failure mode in which the seal
fails at the original interface between the surfaces being sealed.
shall have no influence on the test after the sealing sequence
has begun. These test methods do not cover non-instrumented 3.1.2 burnthrough, n—a state or condition of a heatseal
characterized by melted holes and thermal distortion.
manual procedures employing springs, levers, pulleys and
weights, where test results can be influenced by operator 3.1.2.1 Discussion—Burnthrough indicates that the sealing
conditions (time or temperature, or both) were too high for an
technique.
1.3 Two variations of the instrumented hot tack test are acceptable seal.
3.1.3 cohesive failure, n—a failure mode where either or
described in these test methods, differing primarily in two
respects: (a) rate of grip separation during testing of the sealed both of the sealed webs fails by splitting, approximately
parallel to the seal, and the seal itself remains intact.
specimen, and (b) whether the testing machine generates the
3.1.3.1 Discussion—Refer to Fig. 1. The term may be
cooling curve of the material under test, or instead makes a
measurement of the maximum force observed following a set defined somewhat differently when applied to sealing systems
involving an adhesive material as a separate component.
delay time. Both test methods may be used to test all materials
withinthescopeofthesetestmethodsandwithintherangeand 3.1.4 cooling curve, n—the graphical depiction of the in-
crease in strength of the seal with time, as it cools during the
capacity of the machine employed. They are described in
Section 4. period immediately following conclusion of the sealing cycle
(see Fig. 2).
1.4 SI units are preferred and shall be used in referee
decisions. 3.1.4.1 Discussion—The cooling curve is a plot of hot seal
strength versus cooling time. The portion of the cooling curve
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the of greatest practical significance is the first 1000 ms following
opening of the heatseal jaws.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 3.1.5 cooling time, n—the time interval from when the
heatseal jaws open at conclusion of the sealing cycle, to the
bility of regulatory limitations prior to use. The operator of the
equipment is to be aware of pinch points as the seal jaws come point at which the hot-tack force is determined.
3.1.6 delay time, n—the time interval from when the heat-
together to make a seal, hot surfaces of the jaws, and sharp
instruments used to cut specimens. It is recommended that the seal jaws open at conclusion of the sealing cycle, to the point
at which withdrawal of the sample from between the jaws is
operator review safety precautions from the equipment sup-
plier. initiated.
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These test methods are under the jurisdiction of ASTM Committee F02 on
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Flexible Barrier Materials and are the direct responsibility of subcommittee F02.20 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
on Physical Properties. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Oct. 10, 1998. Published February 1999. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F1921-98R04. the ASTM website.
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