ASTM F 88 covers the measurement of the strength of seals in flexible barrier materials. The test measures the force needed to separate a test strip of the material containing the seal. The mode of failure is also identified. The seal may be between flexible and ridged materials.

Test Summary

Specimens are cut to a specified width. The seal is then peeled apart by holding the two “legs” of the barrier material in the jaws of a force testing stand set to separate at a constant speed between 200 - 300 mm/min. while the force and displacement are continuously measured. The peak force required to separate the seal is reported, this can also be expressed as peak force per width of the seal material in N/m. Depending upon the characteristics of the specimen, it may also be informative to report the average peeling force over the width of the seal as it separates, discarding the first and last part of the force Vs displacement curve.

Test Procedure

Representative samples of the material are cut to 15, 25 or 25.4 mm width perpendicular to the seal. The length of the specimen should be 75 mm plus the width of the seal - see the standard for details. Each leg of the specimen is gripped in the fixed and moving jaws of the force testing stand so the seal is equidistant between the two grips, and aligned laterally so the seal is perpendicular to the direction of movement of the grips. It may be necessary to support the tail of the sample, and this is explained in the standard, if so report the method used.

Test Apparatus

• Tensile tester with grips and suitable range loadcell. This may be a vertical testing stand, or alternatively a horizontally oriented instrument.
• Cutting apparatus

Preparation

Cut a sufficient quantity of strips from a representative sample to a width of 15 mm, 25 mm or 25.4 mm perpendicular to the seal, and 75mm plus the width of the seal in length. If required, condition the specimens in accordance with ASTM E 171.

Method

• 1. If required, condition the samples as per ASTM E 171.
• 2. Cut strips from the sample to the dimensions defined in the standard.
• 3. Clamp the ends of the sample strip into the jaws of the tensile tester with the seal perpendicular to the direction of movement, and equidistant between the fixed and moving jaws.
• 4. If required, support the tail of the test specimen (see the standard for an explanation).
• 5. Set the tensile tester in motion at a speed between 200 and 300 mm/min.
• 6. Record the tensile force and displacement as the seal is peeled apart.

Report

• Record all details necessary to identify the sample including width and machine direction in relation to the direction of pull.
• Report the speed of separation used by the tensile tester, and the method used to support the tail of the sample if appropriate.
• Report the maximum tensile force in newtons encountered as the specimen is stressed to failure. This can also be expressed as force per unit width of the seal in newtons per metre.
• Note the method of failure of the seal.
• Depending upon the characteristics of the force Vs displacement curve, it may be informative to calculate the average force as the seal is separated, discarding the first and final 10% of the force Vs displacement curve.

Mecmesin Test Equipment Required for ASTM F88

• MultiTest force testing stand with loadcell
• Lightweight vice grips
• Emperor software

Alternatively:

• FPT-H1 Horizontal Friction Peel Tear Tester

Link to relevant web pages.

Please refer to the latest official ASTM standard for more detailed information. This overview is intended to provide a basic understanding of the test procedure and suitable equipment to meet the standard.