How to measure peel strength/seal strength

Peel strength and seal strength are two critical properties in the field of packaging, adhesives, and materials science. They measure how much force is required to peel or separate materials that are bonded together, such as adhesive tapes, packaging seals, or laminates.

Understanding these properties is essential for ensuring the durability and integrity of packaging materials, especially for food, pharmaceuticals, medical devices, and other products where secure sealing is necessary to maintain product safety and quality. They are commonly tested using different angles, such as T-peel, 90-degree peel, or 180-degree peel, to measure the average and peak force required for separation.

Peel strength testing using a Texture Analyser is critical across industries to assess the adhesive properties of materials. Below are key applications:

• Packaging tape peel strength testing: Evaluating the peel strength of packaging tapes used for sealing cardboard boxes by measuring the force required to peel a length of tape from the surface. This ensures package integrity during transportation and storage and evaluates ease of opening for consumer convenience. A higher peel strength indicates a stronger adhesive bond, while a lower peel strength suggests that the tape can be peeled off more easily.
• Label adhesion strength assessment: Assessing the adhesive strength of labels by measuring the force needed to peel them from product or packaging surfaces. Adequate adhesion is variable for different applications and balancing peel strength for temporary vs. permanent use is necessary.
• Heat seal strength testing: Testing the strength of heat-sealed packaging by measuring the force required to peel apart the seams of pouches or bags is particularly important where the material must be bonded together securely but still allow the package to be opened without excessive effort.
• Adhesive sealant peel strength analysis: Evaluating the adhesive strength of sealants used in construction by measuring the force needed to peel apart two bonded surfaces.
• Laminated material peel strength assessment: Measuring the force required to separate the layers of laminated materials used in manufacturing to assess the bond strength is important where multiple layers of materials are bonded together. If the layers peel apart easily, the laminate may fail in its application.
• Medical device seal testing: Testing the peel strength of seals in medical device packaging, such as sterilisation wraps, by measuring the force needed to peel apart the seals. This is necessary to ensure sterility of medical packages until point of use is maintained or ensuring seals can withstand sterilisation processes.
• Flexible packaging seal strength analysis: Evaluating the peel strength of flexible packaging materials such as plastic pouches, blister packs and foil seals used in food and pharmaceuticals by measuring the force required to open sealed pouches is essential for maintaining product safety and freshness. Seal strength ensures that the package remains intact until the user opens it.
• Aluminium foil seal peel strength testing: Measuring the peel strength of aluminium foil seals used in pharmaceutical and food packaging by assessing the force required to remove them from containers.
• Electronics component adhesion testing: Assessing the peel strength of adhesive-backed electronic components by measuring the force needed to detach them from circuit boards.

In these examples, a Texture Analyser is used to apply controlled forces/distances to measure peel strength, ensuring product quality, adhesion performance, and packaging integrity.

In a typical peel/seal strength measurement test, two bonded surfaces are pulled apart at a constant rate. The setup typically includes clamping one end of the sample and moving the other surface away to separate the seal.

Several methods are employed to evaluate these properties:

T-peel test: The T-peel test is commonly used to measure peel strength. In this test, the bonded materials are peeled apart at a 180° angle, simulating a typical peeling action for adhesives and packaging materials. The test measures the force required to separate the materials over time or distance.

Seal strength test: The seal strength test involves pulling apart the sealed layers of a package to measure the force required to break the seal. This test is essential for ensuring the package's integrity and assessing its ability to maintain its seal under stress.

90° or 180° peel test: Peel strength is often measured at a 90° or 180° angle, depending on the application. The 180° test measures the force required to pull two bonded materials apart by peeling one directly away from the other, while the 90° test measures the force when one material is peeled perpendicular to the bonded surface.

180° Peel Rig

Tape Unwinding Rig

Articulated Tensile Grips

Miniature Tensile Grips

• Temperature: Temperature can significantly affect the properties of adhesives and the strength of bonds, influencing peel strength measurements.
• Humidity: Environmental humidity levels can impact the performance of adhesives and the integrity of seals, affecting peel strength results.
• Test speed: The rate at which the peeling force is applied during testing can influence the measured peel strength, as materials may respond differently to varying speeds.
• Sample preparation: Consistent and proper preparation of test specimens, including cutting to the correct width and ensuring uniform sealing and conditioning time, is crucial for accurate peel strength measurements.
• Peel angle: The angle at which the peeling force is applied (e.g., 90°, 180°) can affect the measured peel strength and should be specified and controlled during testing.

The Stable Micro Systems Texture Analyser excels in optimising peel strength and seal strength measurements through its comprehensive approach and versatile capabilities. It performs various peel tests, including T-peel, 90-degree, and 180-degree tests, accurately quantifying properties like peel strength, force to commence peeling, and mean peeling force.

The Texture Analyser’s precise measurements and detailed force-distance-time profiles enable in-depth analysis of peel and seal characteristics. Its wide application range covers diverse products from food packaging to medical adhesives, while customisable test settings ensure adaptability to unique sample requirements.

The system's ability to measure critical properties such as seal strength, friction, puncture resistance, and burst strength makes it invaluable across multiple industries. This combination of versatile testing capabilities, precise measurements, comprehensive analysis, and industry-relevant assessments makes the Texture Analyser the ideal choice for researchers and manufacturers seeking to refine product formulations and maintain quality standards in peel and seal strength testing.