ASTM F88 Package Testing Seal Strength Testing of Pouches and Flexible Barrier Materials

ASTM F88 package testing covers the strength of seals in flexible barrier materials. As an ISTA and ISO 17025 certified lab, we realize the importance of flexible barrier testing. Meeting the ASTM F88 testing requirements can be difficult. We understand the challenges and guide companies through the process.

Keystone provides the peace of mind that all of your needs will be met. We partner with customers to achieve package compliance. Keystone takes a consultative approach throughout the entire test program. Our proven process helps avoid product launch delays.

Request a quote to receive testing services customized to your specific needs. Have a question about flexible barrier testing? Contact us and we will determine the best course of action.

Summary of ASTM F88 Seal Strength Testing

The flexible barrier test method is conducted on seals between flexible and rigid materials. Seals tested, per this package test, may be from any source, laboratory, or commercial. Lastly, this test measures the force required to separate a test strip of material containing the seal. The test identifies the mode of specimen failure.

Scope of ASTM F88 Seal Strength of Flexible Barrier Materials

Before the start of the seal strength validation test, the tensile machine is calibrated by the manufacturer’s recommendations. The sealed test specimen is then prepared by cutting it to the specified dimensions. Each leg of the test specimen is then clamped in the tensile testing machine.

For each cycle, the maximum force encountered as the specimen is stressed to failure is reported. Then the mode of specimen failure is identified. The seal is to be tested at a rate of grip separation to 12in/min. If the strip does not peel significantly in the seal area, the average force to failure may have little significance in describing the seal performance.

Significance of ASTM F88 Package Integrity Seal Strength Testing

The ASTM test procedure is a measure for use in process validation, control, and capabilities. Seal strength is not only relevant to opening force and package integrity. It is also used to measure the package processes’ ability to produce consistent seals.

For some applications, the average force to open a seal may be useful. Those cases should be reported. A portion of the force measured when testing materials may be a bending component and not seal strength alone. The effects of the number of fixtures and techniques on the test result can vary. Because of this, consistent use of one technique is recommended.

Technique A: Unsupported

Each tail of the specimen is secured in opposing grips and the seal remains unsupported while the test is being performed.

Technique B: Supported 90 degrees

Each tail of the specimen is secured in opposing grips. The seal remains hand supported perpendicular to the tails while the test is being conducted.

Technique C: Supported 180 degrees

The least flexible tail is supported flat against a rigid alignment plate held in one grip. The more flexible tail is folded 180 degrees over the seal and is held in the opposing grip while the test procedures are performed.

Test Report

Lastly, a report is written including the following basic and specific test information:

  • Complete identification of material being tested
  • Equipment and test method or practice used to form the seals
  • Equipment used to test the seals
  • Ambient conditions during the test. I.e. humidity and temperature
  • Grip separation rate
  • Initial grip separation distance
  • Seal width


ASTM F88 measures the force required to separate a test strip of material containing the seal.


Expert ASTM F88 Flexible Seal Package Testing

Our team strives to give our customers more time and energy on product development instead of testing. In addition to seal strength testing, Keystone has a full scope of flexible package integrity testing expertise including cold chain, accelerated aging, and dye penetration. We can accommodate flexible and rigid packages of all sizes, including large pallets.

Contact us to learn firsthand why so many companies partner with Keystone to achieve their package performance testing and certification needs.


For more referenced ASTM standards and similar testing, please follow the links below:

  • ASTM E171 Practice for Conditioning and Testing Flexible Barrier Packaging
  • ASTM E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method


Interested in the EMC/EMI, climatic, dynamic, shielding effectiveness, or IP Code testing of a product? Follow the corresponding links or for more information.