Testing and influencing factors of peel strength of hot melt adhesive products

Introduction to peel strength testing and influencing factor analysis of hot melt adhesive products. As a widely used adhesive material in packaging, labeling, electronics and other fields, the performance of hot melt adhesive directly affects the appearance and quality of the final product. Peel strength is one of the important indicators for evaluating the quality of hot melt adhesive products, which reflects the ability of the adhesive to resist tearing under external forces. This article will provide a detailed introduction to the testing method for the peel strength of hot melt adhesive and explore possible influencing factors, aiming to provide reference for manufacturers and users. Testing Principles and Methods (1) Testing Principles: Peel strength testing usually uses the T-Peel test method [1]. This method applies a constant or gradually increasing speed to pull two bonded samples, measures the maximum tensile force that can be borne per unit area, and obtains the peel strength value. （2） Specific steps for preparing samples: Select materials of appropriate size as substrates and apply hot melt adhesive under specified conditions. Ensure that the coating is uniform and completely cured. Preparation of sample pairs: According to practical application requirements, different types of sample pairs can be made, such as film/paper, metal/plastic, etc. Pasting the sample: Two pieces of material coated with hot melt adhesive are tightly adhered together in the required direction (usually vertical). Aging treatment (optional): For certain special purpose hot melt adhesives, accelerated aging treatment is required to simulate long-term usage environment. Testing equipment: A specialized peel strength testing machine is used, which can accurately control the stretching speed and record the maximum load. Test conditions: Set appropriate test temperature, humidity, and speed according to different standards (such as ASTM D1876, ISO 9084, etc.). Data collection: Record the maximum load applied during the peeling process and its corresponding displacement. Result calculation: Calculate the peel strength per meter or square inch based on the measured values. Analysis of influencing factors (1) Composition of hot melt adhesive formula The composition of hot melt adhesive includes base resin, plasticizer, stabilizer, coloring agent, etc. Among them, the selection of base resin is particularly crucial because it determines the viscosity and cohesion of the adhesive. In addition, the dosage of plasticizers can significantly affect the flexibility and impact resistance of the adhesive layer. （2） The correct coating process helps to form a uniform thickness and well distributed adhesive film. For example, the coating effect of the roller coating method will be affected by factors such as coating pressure and linear speed ratio; The spraying method needs to consider parameters such as atomization pressure and liquid flow rate. （3） The curing process of hot melt adhesive under curing conditions has a significant impact on its physical properties. Appropriate heating time and temperature can help increase the crosslinking density of the adhesive, enhance its heat resistance and adhesion. （4） Substrate surfaces with different surface characteristics have unique textures and chemical properties, which can affect the wetting ability and adhesion effect of hot melt adhesives. Therefore, when conducting peel strength tests, it is advisable to keep the surface of the substrate clean and free of grease as much as possible. （5） Interface interactions occur between hot melt adhesive and substrate, involving a series of complex interface interactions, including intermolecular forces (van der Waals forces and hydrogen bonding forces, etc.) and the formation of chemical bonds (covalent and ionic bonds, etc.). The strength of these effects is closely related to the peel strength. By scientifically testing the peel strength of hot melt adhesive products, we can gain a deeper understanding of their inherent quality and applicability. At the same time, analyzing various possible influencing factors can help us optimize production processes, improve product quality, and meet the growing market demand. With the continuous progress of technology, it is believed that the hot melt adhesive industry will usher in a broader development space.