ASTM F2029-16(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2029 − 16 (Reapproved 2021)
Standard Practices for
Making Laboratory Heat Seals for Determination of Heat
Sealability of Flexible Barrier Materials as Measured by Seal
Strength
This standard is issued under the fixed designation F2029; 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 1.9 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 These practices cover laboratory preparation of heat
responsibility of the user of this standard to establish appro-
seals. These practices also cover the treatment and evaluation
priate safety, health, and environmental practices and deter-
of heat seal strength data for the purpose of determining heat
mine the applicability of regulatory limitations prior to use.
sealability of flexible barrier materials. It does not cover the
1.10 This international standard was developed in accor-
required validation procedures for the production equipment.
dance with internationally recognized principles on standard-
1.2 Testing of seal strength or other properties of the heat
ization established in the Decision on Principles for the
seals formed by these practices is not included in this standard.
Development of International Standards, Guides and Recom-
Refer to Test Method F88 for testing heat seal strength. These
mendations issued by the World Trade Organization Technical
practices do not apply to hot tack testing, which is covered in
Barriers to Trade (TBT) Committee.
Test Methods F1921.
2. Referenced Documents
1.3 The practices of this standard are restricted to preparing
heat seals using a sealer employing hot-bar or impulse sealing
2.1 ASTM Standards:
methods, or both. D4332 Practice for Conditioning Containers, Packages, or
Packaging Components for Testing
1.4 These practices are intended to assist in establishing
F88 Test Method for Seal Strength of Flexible Barrier
starting relationships for sealing flexible barrier materials.
Materials
Additional guidance may be needed on how to set up sealing
F1921 Test Methods for Hot Seal Strength (Hot Tack) of
conditions for flexible barrier materials on commercial/
Thermoplastic Polymers and Blends Comprising the Seal-
production sealing equipment.
ing Surfaces of Flexible Webs
1.5 Seals may be made between webs of the same or
dissimilar materials. The individual webs may be homoge-
3. Terminology
neous in structure or multilayered (coextruded, coated,
3.1 Definitions:
laminated, and so forth).
3.1.1 dwell time, n—the time interval when the sealing jaws
1.6 Strength of the heat seal as measured by Test Method
areincontactwith,andexertingpressureon,thematerialbeing
F88 is the sole criterion for assessing heat sealability employed
sealed.
in these practices.
3.1.2 heat seal curve, n—a plot of measured seal strength as
1.7 Other aspects of heat sealability, such as seal continuity, a function of sealing temperature at a fixed dwell time and
typically measured by air-leak, dye penetration, visual
sealing pressure.
examination, microorganism penetration, or other techniques,
3.1.3 heat seal strength, n—force per unit width of seal
are not covered by these practices.
required to progressively separate a flexible material from a
1.8 The values stated in SI units are to be regarded as rigid material or another flexible material, under the conditions
standard. The values given in parentheses after SI units are of the test. Also known as seal strength.
provided for information only and are not considered standard.
3.1.4 heat sealability, n—the ability of thermoplastic poly-
mers and blends, when comprising a sealing surface of a
These practices are under the jurisdiction ofASTM Committee F02 on Primary
Barrier Packaging and are the direct responsibility of Subcommittee F02.20 on
Physical Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 15, 2021. Published April 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2000. Last previous edition approved in 2016 as F2029 – 16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2029-16R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2029 − 16 (2021)
flexible web, that defines how well the material bonds to itself with a gasket material such as a silicone rubber (to prevent the
or a dissimilar material upon the application of pressure, heat, test specimen from adhering to the sealing jaws) of known
and dwell (time), as judged by the heat seal curve. durometer and, optionally, an anti-stick coating or covering.
3.1.4.1 Discussion—Since heat seal strength can be mea-
5.1.1.1 Jaw Temperature Control—Each temperature-
sured either while the seal is still hot (hot tack) or after cooling
controlled jaw should have independent temperature control
and stabilizing (ultimate seal strength), a complete evaluation
and the precision of the controlling unit should be known and
of heat sealability of a material may include both tests.
calibrated. The temperature should be verified periodically
using a calibrated pyrometer adequate for the range of use.
3.1.5 hot tack, n—ameasureofthesealstrengthofahotseal
measured at a specified time interval after completion of the 5.1.1.2 Jaw Coatings or Coverings—For the heated jaw(s),
anti-stick or compressible jaw coatings or coverings, such as
sealing cycle but prior to the temperature of the seal reaching
silicone rubber, TFE-fluorocarbon, TFE-fluorocarbon/glass
ambient. Refer to Test Methods F1921.
cloth, or oriented PET film are often used to prevent the test
3.1.6 seal initiation temperature, n—on a heat seal curve,
specimen from adhering to the sealing jaws. For an unheated
the sealing temperature/dwell pressure at which heat seal
jaw, silicone or other heat-resistant rubbers of known durom-
strength first begins to trend upward from zero heat seal
eter may be used. The rubber may be covered with TFE-
strength.
fluorocarbon, TFE-fluorocarbon/glass cloth, or oriented PET
3.1.7 sealing interface, n—the interface of the two web
film.
surfaces being sealed.
NOTE 1—Thick or heat flow-resistant materials will impact the rate of
3.1.8 sealing pressure, n—the force per unit area of seal
heat transfer from jaws to sealing surface. It is important to inspect the
applied to the material by the sealing jaws during the sealing
quality of these materials periodically to prevent loss of properties that
process.
may cause unwanted temperature fluctuations in the sealing process.
3.1.9 sealing temperature, n—the set point of each
5.1.1.3 Jaw Sealing Surfaces—Ideally, the jaw sealing sur-
temperature-controlled sealing jaw. The set point temperature
faces should be parallel when actuated and can be aligned, if
is the controller setting which will produce the desired surface
needed. The uniformity of pressure across the sealing jaws
temperature. Often, the set point temperature will be higher
shouldbechecked.Thismaybedoneusingpressure-indicating
than the surface temperature.
materials or devices by actuating the sealing jaws while at
3.1.10 ultimate seal strength, n—the final value of strength
ambient temperature or at elevated temperatures, as appropri-
that is reached after the heat seal has both cooled to ambient ate.
temperature and achieved stability in strength.
5.1.2 Dwell Time—Variable control and readout of dwell
3.1.10.1 Discussion—Some materials, when cooling from a
time. A range of 0.1 to 10 seconds is desirable. The precision
melt, continue to change in strength over extended periods of
of the dwell time control unit should be known and calibrated.
time after reaching ambient temperature.
NOTE 2—Jaw closure time and set dwell time may be different
depending on heat sealer equipment.
4. Significance and Use
5.1.3 Pressure—Variable control, via a pressure gage or
4.1 Thesepracticesfacilitatethedeterminationoflaboratory
load cell, with readout of the air supply pressure or the sealing
heat sealability of flexible barrier materials. While it is neces-
pressure, respectively.
sary to have a heat seal layer that provides adequate seal
strength for the application, other material properties, such as 5.1.3.1 The applied sealing pressure for machines that have
the overall construction and thickness, will impact the sealing only an air pressure gauge on the air supply line and whose
properties of the material. These practices allow the impact of cylinder size is known should be calculated (neglecting any
changes in material properties on heat sealability to be mea- losses due to mechanical work).The following formula may be
sured. used for this calculation.
4.2 Due to differences between a laboratory sealer and
A
cyl
P 5 P (1)
S D
actual line
manufacturing equipment (for example, scale, size of sealing A
contact
area, and processing speed), there may be a significant differ-
where:
ence between the capability and output of a laboratory heat
P = actual or applied pressure of the sealing jaw,
actual
sealer and that of manufacturing equipment. Hence, care must
P = pressure of the incoming air line,
line
be taken when applying a heat seal curve study as outlined in
A = area of the sealing jaw in contact with material,
contact
these practices to manufacturing equipment. The heat seal
and
curve and the corresponding seal strength data are intended to
A = sum of the cross-sectional areas of all cylinders.
cyl
provide a starting point for determination of sealing conditions
5.1.3.2 When materials are being sealed under pressure and
for full scale manufacturing equipment.
silicone rubber is used on one or both of the jaws, the silicone
5. Apparatus
rubber will compress. When thin materials being sealed are
5.1 Continuous Heat Bar Sealer: narrower than the full length of the sealing jaw, the compres-
5.1.1 Sealing Jaws—Temperature-controlled jaw or jaws sion can be significant enough to change the contact to the full
with appropriate sealing surfaces to provide a flat seal. If only area of the jaw. As a result, the pressure is then distributed
one heated jaw is used, the unheated jaw should be covered across the entire surface and this area is what should be used in
F2029 − 16 (2021)
the pressure calculation.When sealing thick materials, only the area of the jaw. As a result, the pressure is then distributed
area of the seal should be used to calculate the sealing pressure across the entire surface and this area is what should be used in
since contact is limited to the surface of the thicker materials. the pressure calculation.When sealing thick materials, only the
area of the seal should be used to calculate the sealing pressure
5.2 Impulse Sealer
since contact is limited to the surface of the thicker materials.
5.2.1 Impulse Sealing Jaws—Impulse sealing jaw or jaws
with an impulse band applied to it and with appropriate sealing
6. Test Specimen
surfaces to provide a flat seal. If only one impulse sealing jaw
6.1 The number of test specimens shall be chosen to permit
is used, the other jaw should be covered with a gasket material
anadequatedeterminationofrepresentativeperformancebased
such as a silicone rubber (to prevent the test specimen from
on an appropriate rationale. When heat seal strength will be
adhering to the sealing jaws) of known durometer and,
measured at a series of sealing temperatures, an adequate or
optionally, an anti-stick coating or covering.
agreed upon number of replicates shall be used to determine
5.2.1.1 Impulse Sealing Jaw Temperature Control—Each
themeanvalueforeachmaterialateachtemperature.Whenthe
impulse jaw with an impulse band applied to it should have
...