Understanding the Peel Test Curve: What Each Phase Indicates About Adhesion?

Adhesive performance often determines the success of many industrial applications. For instance, sealing packaging or connecting electronics requires strong adhesion. Among the numerous adhesives test methods available, one of the most robust approaches to understanding the strength, continuity, and long-term adhesion is that the peel test will provide you. 

In this post, we shall explore what exactly the peel test curve, as a natural outgrowth of the peel strength test, tells us regarding adhesion.

What is the Peel Test on a Peel Bond Tester?

This peel test is applied to measure adhesion properties. It is employed for tape, labels, laminates, or films. A controlled process of peeling an adhesive away from a substrate makes available considerable amounts of data from which the performances of an adhesive layer under stressful conditions can be derived.

Why Is the Peel Test Curve Important?

The curve obtained from the test gives a graphical representation of the force applied during peeling. This curve further helps professionals conclude whether the adhesives perform and give reliability in practical applications.

Industries Relying on Adhesion Testing

Peel tests are inexhaustible in all industries worldwide and in Saudi Arabia. They are as follows:

Packaging: It provides tamper-proof seals for food items, drugs, cosmetics, etc.

Automobile: Trimmings, rubber seals, temperature sensors, pressure sensors, vibration sensors, etc,

Aerospace: Structural bonding or protective films.

Electronics: Measuring the peel strength of assembly elements such as screens and PCBs.

What is a Peel Strength Test Curve?

A graphical plot of the peeling force, as a function of time or distance, is used to separate the adhesive from the substrate.

Physical Appearance

Shown mostly as a graph of force against displacement or against time, this curve has distinguishable phases describing the behaviour of the adhesive under different conditions.

Purpose

An adhesive peel curve is a diagnostic tool powerful to identify the following indicators:

Key Parameters visible:

• Adhesive Strength: How strong the adhesion is initially.
• Consistency: The consistency in the adhesive's behavior while peeling.
• Failure Modes: The failure modes of the adhesive or substrate when stressed

Key Phases of the Peel Test Curve and Their Implications

1. Maximum Force (Bond Strength)

What It Represents: It is a force that begins peeling. Meaning: Maximum strength at which adhesive starts peeling.

Signs:

High Max Force: There is a high initial bonding force.

Low Max Force: Bonding is poor, mostly as a result of poor surface preparation or the low quality of adhesive.

2. Steady State

What It Represents: This is the steady force necessary for peeling once it has been initiated.

Signs:

Smooth Curve: No variation, which can be indicative of consistent adhesive cohesion and thus assured performance.

Fluctuating Curve: Points to inconsistent application of adhesives, poor material quality or surface finish.

The force is determined by peeling performance.

3. Final State

What It Represents: The adhesive is fully separating from the substrate.

Signs:

Clean Break: Cohesive failure, showing good adhesion within the adhesive layer itself.

Residue Left: Adhesive failure, indicating poor bonding or incomplete curing.

Types of Failures Indicated by the Peel Test Curve

1. Adhesive Failure

This is when the adhesive cleanly separates from the substrate. This indicates that there was a failure in bonding or surface preparation.

2. Cohesive Failure

This occurs when the adhesive layer itself tears apart. This is an indication that the cohesiveness has failed compared to adhesive strength.

3. Substrate Failure

This adhesion is much stronger than the strength of the substrate that would break before tearing in this kind of adhesion.

Determinants of the curve on Peel Seal Strength Tester 

• Material Properties

Types of adhesives - some examples are pressure-sensitive adhesives and heat-activated adhesives

Substrate surface characteristics like smoothness and cleanliness.

• Environmental Conditions

Testing conditions like temperature and humidity- play an important role in the adhesive strength.

• Peel Angle

The common peel angles used are 90° and 180° and offer different information.

• Speed of Peeling

Influences the force measured and the shape of the curve.

FAQs

1. What are adhesive failure and cohesive failure in a Peel Strength Testers peel test?

The adhesive separates from the substrate by cleaning.

In cohesive failure the adhesive layer ruptures or fractures internally.

2. How does the peel angle affect the results of a peel test?

The Peel angle affects the force recorded. A 180° peel test typically records greater forces than a 90° peel test, because the forces are aligned with the substrate.

3. Why is environmental control important in peel testing?

Adhesive properties vary with temperature and humidity. Controlled conditions ensure that the results are reliable and repeatable.

Connect with us and book a demo today!

Contact: +91 9210 903 903

Email: response@prestogroup.com