Peeling Force in Artificial Leather Release Paper: What It Is & How to Measure

In the production of artificial leather, release paper is far more than a protective liner. It is the medium that transfers surface texture, defines gloss, and shapes the tactile quality of the finished PVC or PU film. Among the many technical parameters that govern this process, peeling force stands out as one of the most critical—and one of the most frequently misunderstood.

This guide explains what peeling force means in the context of artificial leather release paper, why it matters on the production line, and how manufacturers can measure it in a repeatable, reliable way.

What Is Peeling Force in Artificial Leather Release Paper?

Peeling force, also referred to as release force or peel strength, is the amount of force required to separate the release paper from the surface of the artificial leather film after the coating and curing process. In a typical production line, liquid PVC or PU resin is applied onto the release paper, cured in an oven, then cooled before the paper is peeled away from the leather film. The force needed to initiate and sustain this separation—expressed per unit width of paper—is the peeling force.

Peeling force is not simply a measure of adhesion. It is the combined result of several contributing factors:

• The surface energy of the release coating applied to the paper.
• The roughness and pattern depth of the textured layer.
• The gloss level of the finished leather surface.
• The chemical compatibility between the resin system and the release layer.
• Processing conditions such as oven temperature, line speed, and cooling efficiency.

Why Peeling Force Matters in Synthetic Leather Production

Peeling force directly affects both production efficiency and final product quality. When the force is too high, the release paper may tear, stretch, or leave silicone residue on the leather surface, leading to scrapped batches and unplanned downtime. When the force is too low, the paper can separate prematurely during conveying or winding, causing texture misalignment and uneven pattern reproduction.

Batch-to-batch consistency is equally important. A uniform peeling force ensures that gloss, texture, and surface feel remain identical across production runs. This is especially critical for car leather, sofa leather, and luggage leather, where panels from different batches must match seamlessly in final assembly. For low-gloss interior films, a plain matte release paper delivers the stable, predictable release profile required for large-surface processing.

Key Factors That Affect Peeling Force

Several variables influence the peeling force of a release paper system. Understanding each one helps manufacturers troubleshoot process deviations and select the most appropriate paper grade.

Release Coating Composition

The type and amount of release agent determine the surface energy of the paper. A higher silicone loading generally reduces peeling force, but excessive dosing can cause the paper to release too quickly, weakening the texture transfer. The coating must be balanced against the resin system and pattern geometry.

Surface Texture and Gloss Level

Deeper textures create a larger surface contact area and a stronger mechanical anchoring effect, which increases peeling force. Fine, low-gloss patterns behave differently from smooth, semi-bright surfaces even when the same resin is used. For instance, the small-litchi texture used in many shoe and luggage leather applications creates a dense grain structure that demands careful peeling-force control to achieve complete pattern reproduction, while a plain matte surface releases more easily and is often preferred for smooth, low-gloss interior films.

When comparing paper grades for a specific application, always review the measured peel data of each texture family rather than relying on visual appearance alone. Guidelines for choosing the right release paper can help narrow down the options by resin type and target finish.

Resin Type and Plasticizer Content

PVC resins with higher plasticizer levels soften more during curing and flow deeper into the micro-structure of the paper, increasing contact area and peeling force. PU and semi-PU systems usually exhibit a different release profile because of their lower surface tension after crosslinking. Always qualify a new resin batch against your release paper before full-scale production.

Processing Temperature and Line Speed

Higher oven temperatures increase resin flow and interface adhesion, while insufficient cooling before peel-off raises the measured force because the film is still slightly soft. Line speed changes also affect the peel angle and strain rate, both of which influence the recorded value.

How to Measure Peeling Force

Peeling force is measured with a tensile testing machine or a dedicated peel force tester, equipped with a load cell, specimen clamps, and a peel-angle fixture. The principle is straightforward: the machine peels the release paper from the artificial leather film at a controlled angle and speed, recording the force throughout the separation process.

Test Methods and Reference Standards

Although no single international standard is written exclusively for artificial leather release paper, manufacturers commonly adapt these well-established methods:

The 90° peel method is generally preferred for release paper evaluation because it keeps the peel angle constant and reduces the influence of paper stiffness on the measurement.

Step-by-Step Measurement Procedure

1. Sample preparation: Cut the release paper and the artificial leather film into test strips of uniform width, typically 25 mm or 50 mm. The peel travel length should be at least 100 mm.
2. Bonding: For release force testing, the release paper is usually tested against a standard adhesive tape or a representative PVC film prepared under controlled conditions. Ensure the bond is free of air bubbles and contamination.
3. Conditioning: Store samples in a standard atmosphere of 23 ± 2 °C and 50 ± 5 % relative humidity for at least 24 hours before testing.
4. Fixture setup: Mount the release paper on the stationary clamp and attach the peeled section of the film to the moving clamp at the chosen angle (90° or 180°).
5. Testing: Start the machine at a constant crosshead speed, usually between 300 mm/min and 1000 mm/min, and record the force over the full peel distance.
6. Data analysis: Calculate the average peel force over the steady-state region of the curve, excluding the initial peak caused by test-start inertia.

For reliable comparison between batches, always document the peel angle, speed, sample width, temperature, and humidity. Each of these parameters shifts the measured value, and undocumented changes make data difficult to interpret.

How to Interpret Peeling Force Data

A typical peeling force curve contains three distinct zones:

• The initial peak: The maximum force needed to start separation, reflecting the static interface adhesion between paper and film.
• The plateau zone: The stable force during continuous peeling, representing the dynamic release behavior of the paper.
• The tail-off: The final decrease near the end of the sample, which is normally disregarded in calculations.

Both the initial peak and the plateau value should be recorded. A high initial peak can trigger jerky release on the production line even if the average peeling force looks acceptable. When a new release paper grade is being qualified, run at least three independent samples per roll and report the mean and standard deviation.

Frequently Asked Questions

Q1: What is the difference between peeling force and release force?

In most practical contexts, the two terms are interchangeable. “Release force” is more often used in the adhesive tape and release liner industry, while “peeling force” appears more frequently when discussing film-to-substrate separation. For artificial leather release paper, both refer to the same physical measurement.

Q2: Which peel angle gives the most reproducible result?

The 90° peel angle is the most repeatable for release paper evaluation because it keeps the peel front stable and minimizes the effect of paper bending stiffness. A 180° peel can be used for quick screening comparisons, but it is more sensitive to sample thickness and flexibility.

Q3: How often should peeling force be monitored in production?

For incoming quality control of release paper rolls, testing one sample per roll is a good starting point. During production, an off-line peel test every shift—or whenever the resin batch, oven temperature, or line speed changes—will help catch drift before it affects finished goods.

Q4: Can peeling force be too low?

Yes. If the release paper separates too easily, the resin may not have cured enough to hold the surface imprint, resulting in faint or incomplete texture transfer. Low peeling force can also cause the paper to shift during winding, creating wrinkles and registration errors.

If you are evaluating release paper grades for a new product line or experiencing release-related quality issues, contact our technical team for application-specific guidance and testing recommendations.