Introduction to Adhesion, Bond, Weld and Peel Testing

There are multiple test methods that evaluate peel strength, seal strength, and adhesion strength and mechanical properties of adhesives and adhesive systems. The tests are wide and varied. Test machines, fixtures and software are engineered for the applications because some of the needs are special compared to other mechanical test requirements.

Adhesive Testing Applications

�  Wood to Wood; Composites; Metal to Metal Structural Adhesives
�  Polymer Based Adhesives, Thin Films
�  Pressure Sensitive Tapes, Labels and Packages
�  Packaging - Medical Devices, Polylaminates, Consumer Products
�  Electronic Components

Tester Spotlight - Peel Test Applications

Peel tests are widespread and apply to proving that a medical device package design is valid, pressure sensitive labels are manufactured correctly, and office supplies, electronics, and other packaging and adhesive products are operating as expected. A peel test measures the force, typically the peak force, required to separate two adhered materials at a specified test speed over a specified length and angle.

Our most popular Standalone Peel Tester (100P225) has several important features that make it stand out in the marketplace:

•  High load measurement resolution and accuracy.
•  High Speed Data Capture
•  Tight Speed control
•  Designed for development and for production
•  Captures and stores several key test parameters including peak and average load

A test sample is typically attached to a moving crosshead with set of mechanical or air operated grips or clamps. The test speed is held constant � typically set by the operator at 10 or 12 inches per minute which is maintained during the test. The peak load and other measurements such as average load or energy at break values are captured and stored in the controller memory until the operator chooses to export the data to a PC. Most peel tests require a load of less than 10 pounds. Statistical data are generated for reports.

Adhesion Characterization Test Equipment (100R225)

Adhesion test systems typically measure and plot load, time and displacement accurately at low gram level loads. These research test systems seek to characterize the behavior of the adhesive system and perform classical tension, compression, and shear tests. Low force pull off or peel tests and tack tests are common. The systems measure resistance to peel or separation from a substrate.

Coatings, linings and finishes that are tested include powder coatings, UV cured, paint films, ceramics, bitumens such as tar enamel and asphalt mastics, epoxies, thermoplastic resins such as vinyl, plastisols and polyethylene, laminates, varnishes, resins such as fluorocarbons, urethanes, phenolics and polyesters, elastomers, and inorganic materials such as zinc, lead and glass.

Industry standard test methods guide the testing process but there are few clear pass/no pass criteria to ensure specific application needs are met. Test equipment must provide accurate machine control and data acquisition, accuracy and repeatability. Test result variation must be minimized from machine to machine. Test fixturing made to meet the specific test requirements is important.

Different Types of Tests:

�  Tension
�  Compression
�  90 degree, 180 degree, and T peel adhesion
�  Release force tests
�  Loop tack measurements
�  Shear
�  Flexural
�  High and low temperature chambers to test adhesives under real life conditions

Tests tend to be either strength tests where peak load is important, or properties tests where capturing and analyzing the load � displacement curve is important.

Application Spotlight - Pressure Sensitive Tape & Labels

Adhesive properties for pressure sensitive labels, packages, and tapes are measured using a standard test surface, a specified angle and test speed. Test results monitor uniformity of adhesive coatings, bonding adhesion strength and force to remove face stock. Sample failures reveal the weak link of a product or process. Cohesive failure produce a tacky residue on both surfaces, adhesive failure reveals a premature peel, failure along the adhesive face stock and test surface, and substrate tearing. When customers improve their testing of materials they purchase, suppliers will be in a better position to meet their needs.

End Users of Test Information:

Peel Adhesion - The force required to remove a label after a length of time at a specific speed and 180 or 90 degree angle - measured in pounds/inch.

Loop Tack - A looped label sample with the adhesive on the outside is lowered into contact with the test substrate, relying on facestock stiffness to regulate force applied. The label is removed and the force required to remove the label is measured in pounds/inch.

Static Shear - A test sample is cut with a liner folded back on one end. The exposed adhesive is attached to a stainless steel panel and placed in a grip with the label facing down and a 250 or 500 gram weight suspended from the label.