ASTM F88
Seal Strength of Flexible Barrier Materials

ASTM F88 is the internationally recognized standard test method for seal strength of flexible barrier materials. It plays a critical role in the packaging industry, especially in medical, food, and pharmaceutical sectors where the integrity of packaging can directly impact product safety.

Understanding ASTM F88 and Its Purpose

ASTM F88 defines procedures for measuring the seal strength of flexible barrier materials. It evaluates how much force is needed to separate a seal—providing insight into the sealing process’s consistency, quality, and durability. According to section 4 of the standard:

Seal strength serves as a key metric in process validation, control, and capability analysis.
A minimum seal strength ensures product protection, while in some cases, limiting maximum seal strength allows for easier opening.
The method supports compliance, traceability, and repeatability—crucial for regulatory environments like medical device and food packaging.

Techniques for Seal Strength Measurement

ASTM F88 outlines three main test techniques to address varying material flexibility and test conditions:

Technique A (Unsupported): Each leg of the sample is clamped without support. Suitable for basic evaluation.
Technique B (Supported 90° by Hand): One tail is hand-supported at a right angle, reducing bending effects.
Technique C (Supported 180°): The less flexible tail is backed by a rigid plate; the flexible tail is folded and pulled. This is the most controlled method for reducing sample flex distortion.

Consistent technique usage is crucial throughout a test series to avoid variations.

Apparatus for ASTM F88 Seal Strength Testing

The tensile testing machine is central to ASTM F88 implementation. It must meet the following requirements:

Constant rate of jaw separation (adjustable between 200 to 300 mm/min).
Accurate measurement of both tensile force and grip displacement (±2%).
Even stress distribution and prevention of specimen slippage.
Optional features like force-travel plotting and average force calculation over a programmable range are desirable for in-depth analysis.

Cell Instruments’ TST-01 Seal Strength Tester is engineered to meet and exceed ASTM F88 standards. It features precision control of jaw speed, high-resolution load cells, and data acquisition systems that support all three test techniques, making it ideal for laboratory and industrial use.

Specimen Preparation and Sampling Guidelines

Specimens must be clean-cut and perpendicular to the seal.
Standard widths are 15 mm or 25 mm, with a ±0.5% tolerance.
The number of test samples should ensure statistical confidence in results.
Testing locations should include multiple spots on the package seal to account for variability.

Conditioning and Aging Considerations

Before testing, specimens may require conditioning based on their intended storage or use conditions. Heat-seal stability and environmental exposure (e.g., humidity, temperature) influence seal performance. ASTM recommends conditioning protocols as per Practice E171 or test-specific criteria.

Test Procedure According to ASTM F88

Calibrate the tensile machine according to the manufacturer’s instructions.
Cut and prepare specimens as per dimension guidelines.
Clamp each leg securely with equal alignment. Avoid pre-stressing the seal.
Center the seal line and ensure perpendicular alignment with the direction of pull.
Test at the grip separation speed of 200–300 mm/min.
Record results, including maximum force, average force (if needed), and force-travel curves.
Document the technique used and any tail orientation, especially when comparing across batches.

Applications of ASTM F88 in Packaging Industries

Medical Packaging: Ensures sterile barriers are strong enough to protect contents, yet peelable.
Food Packaging: Validates that seals prevent contamination and leakage during transportation.
Pharmaceuticals: Critical for regulatory compliance in drug safety and packaging uniformity.

Consistent seal strength testing improves packaging reliability, consumer satisfaction, and compliance with ISO and FDA requirements.

Why Choose Cell Instruments for Seal Strength Testing

Cell Instruments’ TST-01 Seal Strength Tester offers full compliance with ASTM F88, high-speed testing, customizable grips for different materials, and intuitive software for data logging and reporting. Our equipment is used by global clients across packaging, medical device, and quality assurance laboratories. We also offer customized test automation and multi-functional systems for combined tensile, peel, and burst testing.

ASTM F88 is the gold standard for packaging seal strength testing of flexible barrier materials. By following this standard, manufacturers and quality control professionals can ensure product safety, packaging consistency, and regulatory compliance. For precise and reliable seal strength testing, Cell Instruments provides high-quality instruments and technical support to help you achieve operational excellence.

FAQs

1. What is the primary purpose of ASTM F88 testing?
To evaluate the seal strength of flexible packaging and ensure consistent seal integrity during manufacturing and handling.

2. Which test technique (A, B, or C) should I use?
It depends on material type and application. Technique C is preferred for reducing variation due to material flex.

3. Can the test machine calculate average seal strength automatically?
Yes. Advanced testers like Cell Instruments’ TST-01 offer programmable grip travel range to compute average seal strength.

4. How many specimens should I test per sample batch?
You should test a statistically relevant number, often 5–10 samples, from different seal locations for accuracy.

5. Can this method be used for packages with visual defects?
Yes, but the testing objective must guide this decision. Including defective seals can help assess worst-case performance.

ASTM F88 Seal Strength of Flexible Barrier Materials