Seal Strength — ASTM F88

The heat seal strength test measures the force required to separate, on a tensile tester, a strip cut through the sealed area of a flexible package. The result is given as force per unit width, and the mode of separation is also recorded.

The purpose is to verify the heat-sealing parameters (temperature, pressure, time) on the filling line are set correctly and the package will not open during handling.

• Flexible food packaging and pouches
• Sterile medical device packaging
• Blister lidding films
• Stand-up pouch and sachet packaging
• Vacuum packaging

• ASTM F88peeling resistance in sealing seam test

Specimen width

Defined in the standard; the result is given per unit width, e.g. N/15 mm

Tensile speed

Constant speed defined in the standard

Grip technique

ASTM F88 defines three different grip techniques; the result varies by technique

• Tensile tester with pneumatic grips
• Specimen cutter
• Laboratory heat-sealing press (for parameter optimisation)
• Conditioning chamber

• Specimens sealed with the production-line parameters
• Strips cut perpendicular to the seal area
• Specimens must be taken from different edges of the package
• Sealing parameters (temperature, pressure, time) must be provided

The test is short; duration is set by specimen preparation and the number of specimens. Duration increases if a parameter optimisation study is performed.

1. 1Specimens are conditioned.
2. 2Strips of the defined width are cut perpendicular to the seal area.
3. 3The strip ends are mounted in the grips using the technique defined in the standard.
4. 4It is pulled at constant speed and the force-extension curve is recorded.
5. 5Maximum and average separation force are calculated.
6. 6The mode of separation (peel, delamination, material break) is recorded.

The acceptance criterion is the minimum seal strength in the specification. For sterile barrier systems, separation is also required to occur without fibre tear-out and in a controlled manner — very high strength can also be a problem, since the material can tear on opening and compromise sterility.

The mode of separation carries as much information as the numeric value: a clean peel points to correct parameters, while delamination or material break points to excessive temperature. Low strength stems from insufficient temperature, pressure, or contamination in the seal area.

• Package and film structure identification
• Sealing parameters
• Standard applied and grip technique
• Individual and average force values (N/15 mm)
• Mode of separation and observations

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

• (EU) 2017/745 Medical Device Regulation

The section below describes the field that the Seal Strength test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

• Box Compression
• WVTR
• OTR
• Compression
• Burst
• Edge Crush
• Drop
• Vibration
• Shock
• Leak
• Peel
• Migration