When the adhesion property of film bonded to the substrate is tested, this is called the peel test. Usually, this is done by the process of tensile. The adhesive strength is also called the adhesive fracture toughness; this determines the peel strength. Physical testing of any product’s packaging can be done with the help of peeling. Peeling can also tell a lot about the product’s packaging properties. Also, it can describe manufacturing processes such as bonding strength, sealing consistency, bond durability, adherence ability, cohesive properties of the interface, and other parameters.
Moreover, peel tests are performed mainly for two reasons:
- The Assessment of uniformity of the adhesion for the type of pressure-sensitive adhesive interface. Between the adhesives and the adherents, this indicates a bad adhesion.
- For determining the acceptable for the adhesive or the consumer, distinguishing between acceptable and unacceptable criteria is done.
How does a peeling test is performed?
For measurements, requirements are:
● a force gauges
● suitable grips
● a motor-driven mechanism. This is used to pull the product under Test at a controlled angle and steady rate.
These are the steps one can follow to perform a peel test:
Step 1: The unbounded ends and the bent will clamp the test specimen in the test grips.
Step 2: Apply the load.
Step 3: Once the load is applied, measure and record the force’s response.
Step 4: Ideally, the response should be recorded for the displacement versus force curve to initiate and propagate.
Types of peel test:
There are three types of peel tests to test the adhesive’s strength and efficiency suitable to the industry standards. Let us briefly see what these three peel tests are and how they are performed:
- T-Peel Test: A specific type of tensile is used to separate the two flexible adhesives bonded together. The specimens for this Test are prepared with the two ends open. Both the ends are placed into a fixed grip. Once they are correctly set, both the grips are moved away from each other. Once both the grips are fully separated, the substrates are peeled off from each other. The force applied to the substrates during the whole testing is then measured by the load cell of the instrument.
- 90° Peel test: In the 90° Peel test, on rigid substrates, the test specimen is placed. In the grip, the open ends of the adhesive are placed. Once they are correctly set, they are separated by pulling them away. This movement causes the adhesives to peel off from the substrate. Again the force is measured via the load cell present in the instrument. The critical point in the testing is that the pressure applied on the adhesive is perpendicular to the peeling direction.
- 180° Peel Test: This Test is conducted similarly, just like the 90° test. The only difference between the two is the direction of the force applied. The pressure to the adhesive is used in the same line as the peeling direction.
This was a brief regarding the peel test and how it can be conducted. Also, the requirements to perform a peel test and the type of peel test. Peel tests play a vital role in the product designing and manufacturing industry.