Seal Strength Package Testing

What is Seal Strength Integrity Testing?

Seal strength testing measures the strength of seals in flexible materials. This test type can also be conducted on seals between a flexible material and rigid material. Ultimately, this ensures the proper bonding of materials to maintain package integrity.

As an ISTA and ISO 17025 certified lab, we realize the importance of seal strength package testing. Meeting the seal integrity regulatory compliance requirements can be difficult. We understand the challenges and guide companies through the process.

Request a quote to learn why we are one of the fastest-growing package test labs in the country. Have a question about seal strength integrity testing? Contact us and we will determine the best course of action.

Why is Seal Strength Package Integrity Testing Important?

Seal strength package integrity testing is crucial in preserving the quality and integrity of products. Properly sealed packages prevent contamination, spoilage, and degradation due to environmental factors such as moisture, oxygen, and light. By evaluating the seal’s strength, the testing process ensures that packages effectively protect the contents from external elements, preserving their freshness, efficacy, and shelf life.

In the case of pharmaceuticals, medical devices, or food products, compromised seals can result in product contamination, rendering them unfit for consumption or use. Seal strength package integrity testing helps identify weak or inadequate seals, allowing manufacturers to address potential safety risks before the products reach consumers. Seal failure can lead to product leakage, spilling, or exposure, posing safety hazards to consumers.

Lastly, Seal strength package integrity testing is often mandated by regulatory bodies to ensure compliance with safety and quality standards.

Seal Strength Package Testing Procedures

ASTM F88, Seal Strength Testing of Pouches and Flexible Materials covers the measurement of the strength of seals in flexible barrier materials. First, a sample is chosen to represent an adequate amount of packaging units. Next, the samples are conditioned to 23 °C and a relative humidity of 50%. The units under testing may be subjected to 40 hours of conditioning.

After conditioning, the tensile machine is calibrated according to the testing standard. One of three seal strength testing procedures is chosen.

Technique A: Each tail of the specimen is secured in opposing grips and the seal remains unsupported during testing.

Technique B: Each tail of the specimen is secured in opposing grips and the seal remains hand-supported at a 90-degree perpendicular angle to the tails.

Technique C: The least flexible tail is supported flat against a rigid alignment plate held in one grip. The more flexible the tail is folded 180 degrees over the seal and is held in the opposing grip. 

A tensile testing machine carries out the seal strength testing. The machine is equipped with a device for recording the tensile load and amount of separation of the grips. Flexible materials are indicated as materials with flexural strength and thickness permitting a turn back at an appropriate 180 degrees.


Packaging Seal Integrity Testing


The maximum seal force must also be considered. However, for some applications, the average force to open a seal may be useful. The average force required to separate a test strip of material containing a seal may indicate a failure.

Lastly, a test report is written with the following information. The list below is not intended to be all-inclusive.

  • Identification of the material being tested
  • Equipment and test method used
  • Ambient conditions during testing
  • Grip separation rate
  • Initial grip separation distance
  • Number of specimens tested
  • Any pertinent information that can affect test results

Keystone Package Testing Seal Strength Equipment and Capabilities

Keystone utilizes numerous pressure delivery systems, vacuum chambers, and open/closed package test fixtures to provide expert seal strength package integrity testing. Our dozens of thermal chambers range from reach-in to large walk-in chambers up to 1,300 cu. Ft.

Keystone Package Testing also owns numerous shakers, compression machines, and dynamic shock machines to provide the peace of mind that all your package integrity needs are met under one roof.

Expert Regulatory Compliance Package Test Laboratory

In addition to sterile barrier compliance testing, Keystone Package Testing has a full scope of expertise including vibration, accelerated aging, and compression. We can accommodate flexible and rigid packages of all sizes, including large pallets. Our team strives to give our customers more time and energy on product development instead of testing.

Contact us to learn first hand why so many companies partner with Keystone to achieve their package certification needs. Request a quote to receive testing services customized to your specific needs. For more information on flexible package compliance testing, please refer to the following standards.


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