ASTM F88-00
(Test Method)Standard Test Method for Seal Strength of Flexible Barrier Materials
Standard Test Method for Seal Strength of Flexible Barrier Materials
SCOPE
1.1 This test method covers the measurement of the strength of seals in flexible barrier materials.
1.2 The test may be conducted on seals between a flexible material and a rigid material.
1.3 Seals tested in accordance with this test method may be from any source, laboratory or commercial.
1.4 This test method measures the force required to separate a test strip of material containing the seal. It also identifies the mode of specimen failure.
1.5 SI units are preferred. The values given in parentheses are for information only.
1.6 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 consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:F88–00
Standard Test Method for
Seal Strength of Flexible Barrier Materials
This standard is issued under the fixed designation F 88; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1.1 Discussion—The average force normally is calcu-
lated by the testing machine from the digitized plot of force
1.1 This test method covers the measurement of the strength
versus grip travel. The plot starts from zero force after slack
of seals in flexible barrier materials.
has been removed from the test strip. The initial ramp-up from
1.2 The test may be conducted on seals between a flexible
zero to the force level required to peel the seal is not indicative
material and a rigid material.
of seal strength, and data from that part of the curve should not
1.3 Seals tested in accordance with this test method may be
be included in the calculation of average strength, nor should
from any source, laboratory or commercial.
the return to zero following complete failure of the specimen.
1.4 This test method measures the force required to separate
The amount of data actually discarded on each end of the
a test strip of material containing the seal. It also identifies the
measured seal-profile curve must be the same for all tests
mode of specimen failure.
within any set of comparisons of average seal strength (see
1.5 SI units are preferred. The values given in parentheses
6.1.1 and 9.8.1).
are for information only.
3.1.2 flexible, adj—indicates a material with flexural
1.6 This standard does not purport to address all of the
strengthandthicknesspermittingaturnbackatanapproximate
safety concerns, if any, associated with its use. It is the
180 degree angle.
responsibility of the user of this standard to consult and
3.1.3 maximum seal strength, n—maximum force per unit
establish appropriate safety and health practices and deter-
width of seal required to separate progressively a flexible
mine the applicability of regulatory limitations prior to use.
material from a rigid material or another flexible material,
2. Referenced Documents
under the conditions of the test.
2.1 ASTM Standards:
4. Significance and Use
D 882 Test Methods for Tensile Properties of Thin Plastic
2 4.1 Seal strength is a quantitative measure for use in process
Sheeting
validation, process control and capability. Seal strength is not
D 1898 Practice for Sampling of Plastics
only relevant to opening force and package integrity, but to
E 171 Specification for Standard Atmospheres for Condi-
measuring the packaging processes’ ability to produce consis-
tioning and Testing Flexible Barrier Materials
tent seals. Seal strength at some minimum level is a necessary
E 691 Practice for Conducting an Interlaboratory Study to
package requirement, and at times it is desirable to limit the
Determine the Precision of a Test Method
strength of the seal to facilitate opening.
3. Terminology
4.1.1 The maximum seal force is important information, but
for some applications, average force to open the seal may be
3.1 Definitions:
useful, and in those cases also should be reported.
3.1.1 average seal strength, n—average force per unit width
4.2 When a seal fails adhesively (peel seal) the value of the
of seal required to separate progressively a flexible material
bond strength measured is reported. A cohesive failure of the
from a rigid material or another flexible material, under the
bond, delamination, or failure elsewhere in the test strip
conditions of the test.
indicates that the substrate, not the seal interface, would be the
limiting factor in the strength of a package. In those cases seal
strength may be reported as “no less than” the strength
This test method is under the jurisdiction of ASTM Committee F2 on Flexible
measured.
Barrier Materials and is the direct responsibility of Subcommittee F02.30 on Test
4.3 A portion of the force measured when testing materials
Methods.
may be a bending component and not seal strength alone. A
Current edition approved May 10, 2000. Published July 2000. Originally
published as F 88 – 68. Last previous edition F 88 – 99.
number of fixtures and schemes have been devised to hold
Annual Book of ASTM Standards, Vol 08.01.
samples at various angles to the pull direction to control this
Discontinued 1998; see Annual Book of ASTM Standards, Vol 08.01.
4 bending force. Because the effect of each of these on test
Annual Book of ASTM Standards, Vol 15.09.
Annual Book of ASTM Standards, Vol 14.02. results is varied, consistent use of one technique throughout a
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F88
test series is recommended. Examples of fixtures and schemes 8. Aging and Conditioning
are illustrated in Fig. 1.
8.1 In the absence of information showing that heatseal
strength stability of the materials under test is reached in
5. Interferences
shorter times, condition and test sealed materials in accordance
5.1 The value obtained for seal strength can be affected by
withSpecificationE 171,withaminimumconditioningtimeof
properties of the specimen other than seal strength. These
40 h or longer if shown to be required to reach stability.
interferences are discused in the annex.
8.2 Heatsealconditioningperiodsmaybeshortenedtotimes
determined by experimentation as sufficient to achieve seal
6. Apparatus
strength stability.
6.1 Tensile Testing Machine—A testing machine of the
8.3 Modificationofconditioningpracticesmaybenecessary
constant rate-of-jaw-separation type. The machine shall be to meet specific test objectives, such as the measurement of
equipped with a weighing system that moves a maximum
seal strength at specified storage or handling temperature.
distance of 2 % of the specimen extension within the range
being measured. The machine shall be equipped with a device
9. Procedure
for recording the tensile load and the amount of separation of
9.1 Calibrate the tensile machine in accordance with the
the grips; both of these measuring systems shall be accurate to
manufacturer’s recommendations.
62 %. The rate of separation of the jaws shall be uniform and
9.2 Prepare sealed test specimens for testing by cutting to
capableofadjustmentfromapproximately200to300mm(8to
the dimensions shown in Fig. 2. Edges shall be clean-cut and
12 in.)/min. The gripping system shall be capable of minimiz-
perpendicular to the direction of seal. Specimen legs may be
ing specimen slippage and applying an even stress distribution
shorter than shown, depending on the grip dimensions of the
to the specimen.
testing machine.
6.1.1 If calculation of average seal strength is required, the
9.3 Clampeachlegofthetestspecimeninthetensiletesting
testing machine system shall have the capability to calculate its
machine. The sealed area of the specimen shall be approxi-
valueoveraspecifiedrangeofgriptravelprogrammablebythe
mately equidistant between the grips. Recommended distance
operator. Preferably, the machine shall have the capability also
between grips (initial unconstrained specimen length) is:
to plot the curve of force versus grip travel.
Fin and Hot-Wire Seals
6.2 Specimen Cutter, conforming to the requirements of 5.4
A
Highly extensible materials: 10 mm (0.39 in.)
A
ofTest Methods D 882, sized to cut specimens to a width of 25
Less extensible materials: 25 mm (1.0 in.)
Lap Seals: X + 10
mm (0.984 in.), 15 mm (0.591 in.), or 25.4 mm (1.00 in.).
B
mm
Tolerance shall be 60.5 %.
A
Grip separation distance is recommended to be limited for highly extensible
materials (100+%elongation at seal failure) to minimize interferences (see
7. Sampling
annex).
B
Refer to Fig. 2 for definition of X.
7.1 The number of test specimens shall be chosen to permit
an adequate determination of representative performance. 9.4 Center the specimen laterally in the grips. Align the
specimen in the grips so the seal line is perpendicular to the
Practice D 1898 provides guidance for test specimen selection.
direction of pull, allowing sufficient slack so the seal is not
7.2 Testing of samples with visual defects or other devia-
stressed prior to initiation of the test.
tions from n
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