Peel strength, the average force required to separate two bonded materials from one another, is a property applicable to various industries including aerospace, automotive, adhesives, packaging, biomaterials, microelectronics, and more. Peel test data is used to determine the quality of the adhesive joint and, where applicable, provides information on the effects of processes and of the environment on the adhesive-adherend interface strength.

How To Measure Peel Strength

Peel tests are constant-speed tests in the tensile direction. In material testing, peel strength is calculated after measuring and averaging the load to peel the specimen and dividing the average load by unit width of the bond line. The load data used in peel strength calculations is derived from the flat portion of the load vs. position curve. 

ASTM D3330 Test F, Load-Position curve generated on ADMET MTESTQuattro® software

Types of Peel Tests

A universal testing machine equipped with a peel fixture is used to perform peel tests. Simply by changing the fixturing, the same universal testing machine can be used to run various peel test methods. The main difference between these methods is the angle of peel. Common peel tests include:

  • 45 degree peel tests
    • Most applicable to the food packaging industry
  • 90 degree peel tests
  • 180 degree peel tests
    • Peel test method where the peel arms are clamped in the tensile grip jaws and pulled apart 
  • 180 degree T-peel tests
    • Most commonly used with thin-gauge metal adherends
    • Lowest peel strength values 
  • Climbing drum peel tests
    • Peel test setup to peel the specimen at a constant peel radius

Standard Peel Test Methods

Common peel testing standards include:

Recommended Equipment

A universal testing machine equipped with the appropriate capacity load cell and peel fixturing (peel fixtures may vary depending on the type of peel test method followed) is required to run peel strength tests. We recommend the system to be controlled by a closed loop controller that can keep constant rate throughout the tests and have the ability to calculate the average peel strength data over a specified distance. Below is a featured product configuration for peel strength testing.

eXpert 7600 Universal Tensile Testing Machine

eXpert 7600 series Universal Testing Machines are single column testing systems with capacities up to 5kN (1,125lbf). These systems can be used to perform multiple tests and are easily tailored to fit the needs of the end-user.

eXpert 7600 performing a 90 degree peel test

Controller

Controllers available with ADMET systems, such as the MTESTQuattro PC-based controller or the eP2 digital controller, are able to average peel strength loads over a specified distance and simplify reporting through a variety of means.  Users have the ability to select from a list of built in methods or design their own unique tests.

MTESTQuattro Test Report for ASTM D1876 T-Peel Test

Peel Fixtures

selection of grips and fixtures also offer users the ability to perform various peel tests and design their own experiments. These accessories include 90 degree peel fixtures, loop tack fixtures, and 180 degree grips for peel tests.

Conclusion

Peel strength is a critical parameter in the overall quality of the final product and peel testing is conducted by many industries to analyze the strength of materials. Utilizing ADMET testing equipment, you can confidently report peel test results knowing that the system has been engineered to meet all accuracy requirements specified in major standards organizations including ASTM, ISO, TLMI, PSTC. Contact an ADMET Sales Engineer for further information on how we can help with your peel testing applications.

 

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