ASTM F88/F88M, "Standard Test Method for Seal Strength of Flexible Barrier Materials," provides a quantifiable way to measure the seal strength of a package. This standard is part of integrity validation testing. The seal strength is essential for the validation and control of the packaging process, as it indicates the ability of the process to consistently produce effective seals. Not only is seal strength crucial for package integrity and ease of opening, but it is also required at a minimum level for the package to meet specific requirements.
Three different techniques are recommended for this testing procedure: Techniques A, B, and C. These different techniques accommodate varying levels of support for the seal being tested and address the issue of bending force that may influence the testing results.
Technique A, known as "Unsupported," involves securing each tail of the specimen in opposing grips with the seal remaining unsupported throughout the testing.
Technique B, called "Supported 90° (By Hand)," also involves securing each tail of the specimen in opposing grips, but the seal is hand-supported at a 90° angle perpendicular to the tails while the test is being conducted.
Lastly, Technique C, known as "Supported 180°," involves supporting the least flexible tail flat against a rigid alignment plate held in one grip. The more flexible tail is folded 180° over the seal and held in the opposing grip during the test.
The scope of this test method is comprehensive, covering the measurement of the strength of seals in flexible barrier materials. This can be applied to seals between a flexible and a rigid material.
An alternative method is mentioned: EN 868-5 Annex D.
The testing method measures the force needed to separate a test strip of material containing the seal and identifies the mode of specimen failure. This distinguishes it from other test methods such as ASTM F2824, which measures the mechanical seal strength by separating an entire lid from a rigid or semi-rigid round container, and ASTM F904, which measures the bond strength or ply adhesion of laminates made from flexible materials.