Overview
The peel strength tester is an instrument used to determine the resistance to separation at the bonding interface between materials. In hot melt adhesive resin applications, the device quantifies the bonding properties of the adhesive to the adhesive to the adhesive by simulating the actual peel process. Its working principle is usually based on constant speed stretching, which separates the bonded specimen at a specific angle (e.g., 180° or 90°) and speed, while recording the change in force value during the peeling process in real time. The measurement results are a key reference value for evaluating the initial adhesion, durability and process adaptability of hot melt adhesives.
Measurement principle
The hot melt adhesive resin is coated in a molten state and cooled and cured, forming a bonding interface with the adhered substrate. Peel force measurements reflect the energy required for interface failure and typically involve cohesive failure, interfacial adhesion failure, or mixed failure modes. According to the classical adhesion theory, the peel force F can be related to the interface energy γ and the peel width b, and its simplified relationship can be expressed as:
F = γ × b × f(θ, v)
where θ is the peeling angle, v is the peeling velocity, and the function f represents the geometry and rate-dependent properties. The actual measurement needs to be performed in a standard environment to control the effect of temperature and humidity on the viscoelasticity of the hot melt adhesive.
Measurement method
Common peel tests follow a number of domestic and foreign standards, such as ASTM D3330, GB/T 2792, etc., which specify specimen preparation, peeling angle, speed and environmental conditions. A typical test involves applying a hot melt adhesive to a standard substrate (e.g., metal, plastic, paper) to form a bonded specimen of specified width and length, which is then peeled off at a constant speed on a testing machine. The data acquisition system records the peel force curve, usually taking the average or median value of the curve as the peel force result. Examples of test conditions are as follows:
| Peel angle | 180° |
| Peel speed | 300 mm/min |
| Specimen width | 25 mm |
| Ambient temperature | 23±2°C |
| Relative humidity | 50±5% |
Key parameters of the instrument
To ensure measurement accuracy, the testing machine needs to meet the requirements of force resolution, speed stability and centering accuracy. The force sensor range should cover the expected peel force range, usually choosing to have the measurement between 10% and 90% of the full scale. Calibration is performed according to JJG 475 or similar procedures, with force verification by standard weights or force gauges, while checking for speed errors and system rigidity. Regular calibration reduces system errors and ensures data comparability.
Notes:
The peel force curve fluctuations reflect the bonding uniformity and failure mode. Steady curves indicate uniform interface failure, while periodic fluctuations may suggest cohesive failure or substrate deformation. In the evaluation of hot melt adhesives, it is necessary to combine the comprehensive analysis of process parameters such as adhesive layer thickness, opening time, and curing temperature. When measuring, attention should be paid to the consistency of sample preparation, avoid edge effects and eccentric peeling, and record the deviation of environmental conditions. Averaging multiple tests improves the reliability of the results.
References
ASTM D3330 Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape
GB/T 2792 Test method for peel strength of adhesive tape
ISO 8510-2 Adhesives — Peel test for a flexible-bonded-to-rigid test specimen assembly — Part 2: 180° peel
Liu Jingli, Adhesive Testing Technology, Chemical Industry Press