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Explanation of viscosity of TPU hot melt adhesive film
​TPU hot melt adhesive film is a polymer material based on polyurethane elastomer. It has good adhesive properties and weather resistance and is widely used in home, industry, automobile and other fields. This article will introduce in detail the viscosity of TPU hot melt adhesive film and its influencing factors, and discuss how to improve its viscosity.
2023-10-17
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Explanation of viscosity of TPU hot melt adhesive film

    TPU hot melt adhesive film is a polymer material based on polyurethane elastomer. It has good adhesive properties and weather resistance and is widely used in home, industry, automobile and other fields. This article will introduce in detail the viscosity of TPU hot melt adhesive film and its influencing factors, and discuss how to improve its viscosity.

    Viscosity is one of the most important physical properties of TPU hot melt adhesive film. It is defined as the ease with which the adhesive film flows at a certain temperature. If the viscosity is too low, the adhesive film will be too soft, resulting in insufficient adhesion; while if the viscosity is too high, the adhesive film will be too hard, resulting in reduced adhesion. Therefore, viscosity control is crucial for the application of TPU hot melt adhesive film.

    Factors affecting the viscosity of TPU hot melt adhesive film

    Raw material The raw material of TPU hot melt adhesive film is mainly polyurethane elastomer, in which the type and proportion of polyol and diisocyanate have a great influence on the viscosity. For example, the use of low molecular weight polyols and low molar mass diisocyanates can reduce the viscosity of TPU hot melt adhesive films. Temperature is another important factor affecting the viscosity of TPU hot melt adhesive films. As the temperature increases, the viscosity of the TPU hot melt adhesive film will decrease and the fluidity will increase, which will help improve the adhesion and wettability. Therefore, in practical applications, the increased plastic viscosity of the TPU hot melt adhesive film can be controlled by adjusting the heating temperature. Adding plasticizer during the preparation process of the TPU hot melt adhesive film can reduce the glass transition temperature of the polymer, thus Reduce viscosity to make the film flow more easily. Commonly used plasticizers include phthalates, camphor

    Methods to increase the viscosity of TPU hot melt adhesive film

    1. Increase the degree of polymerization of polyurethane elastomer

    By increasing the degree of polymerization of polyurethane elastomer, the molecular weight of the TPU hot melt adhesive film can be increased, thereby increasing its viscosity and hardness. For example, high viscosity TPU hot melt adhesive films can be prepared by using high molar mass diisocyanates and short-chain glycols to synthesize polyurethane elastomers.

    2. Blending modification

    Blending modification of polyurethane elastomer with other polymer materials can also increase the viscosity of TPU hot melt adhesive film. For example, mixing polyurethane elastomer with polyester glycol can produce a TPU hot melt adhesive film with high viscosity and good weather resistance.

    3. Microencapsulation

    Microencapsulation is a technology that encapsulates small particle materials in a polymer matrix, which can improve the adhesion of the polymer surface and thereby increase the viscosity of the TPU hot melt adhesive film. When preparing microcapsules, their properties can be optimized by controlling the particle size, shape, and distribution of the particulate material.

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TPU hot melt adhesive film vs anaerobic adhesive: "Scene flexibility" difference in automotive interior bonding
2025-09-11
​From the perspective of curing conditions, TPU hot melt adhesive film does not need to rely on special environments, while anaerobic adhesives are severely restricted by "auerobicity". The curing principle of anaerobic glue is to undergo polymerization under conditions of lack of oxygen and catalyzed by metal ions (such as iron and copper). If it is in an environment where air circulation or metal substrates are not available, the curing speed will be greatly slowed down or even unable to cure. In automotive interiors, most bonding scenarios are "open" (such as bonding the door panel skin to PP substrate, and the ceiling fabric to the sponge), the air can freely contact the bonding surface, and the substrate is mostly non-metallic (PP, ABS, fabric, etc.), lacking metal ion catalysis, and additional catalyst is required when using anaerobic glue, and the curing time is as long as several hours, which is difficult to meet the needs of industrial production. The TPU hot melt adhesive film only needs to be melted by heating (120-160℃) and can be cured after pressurization and cooling. It does not need to rely on the ambient oxygen concentration or the base material. It can be cured stably in open or closed bonding scenarios, and the curing time only takes a few dozen seconds to a few minutes, adapting to the fast-paced needs of the interior production line.
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