Bonding strength of hot melt adhesive films

The bonding strength of hot melt adhesive film is related to the following factors:

1. The properties of the hot melt adhesive film itself

Composition type: Hot melt adhesive films with different compositions, such as EVA (ethylene vinyl acetate), PA (polyamide), PES (polyether sulfone) and TPU (thermoplastic polyurethane), have different chemical structures. The vinyl acetate content of EVA hot melt adhesive film will also affect its bonding strength. When the vinyl acetate content is higher, the flexibility and viscosity of the adhesive film will increase, which is conducive to the bonding of some flexible materials.

Molecular weight and distribution: The molecular weight determines the cohesive strength of the hot melt adhesive film. The film with a higher molecular weight has stronger interaction between molecular chains, greater cohesive energy, and can withstand greater external forces without breaking easily, thereby increasing the bonding strength.

Hot melt adhesive films with narrow molecular weight distribution have more uniform performance and can better exert their bonding properties during the melting and curing process, avoiding the decrease in bonding strength due to local performance differences.

Additives: Tackifiers in hot melt adhesive films can increase the adhesion between the film and the surface of the adherend. Antioxidants can prevent the performance of hot melt adhesive films from degrading due to oxidation during long-term use or high-temperature processing. Appropriate antioxidants can maintain the performance of the film and ensure the stability of the bonding strength.

2. Nature of the adherend

Material type: Different materials have different surface energies. For plastic materials with low surface energy, such as polytetrafluoroethylene, it is necessary to specially treat the film or select a special film to improve the bonding strength.

Surface condition: The cleanliness of the adherend surface is crucial. If there are impurities such as oil, dust, etc. on the surface, it will hinder the effective contact between the hot melt adhesive film and the adherend, reducing the bonding strength.

Appropriate surface roughness can increase the mechanical interlocking effect between the hot melt adhesive film and the adherend.

3. Bonding process factors

Temperature control: The appropriate heating temperature can make the hot melt adhesive film fully melted and have good fluidity, so as to better wet and penetrate the surface of the adherend. If the temperature is too low, the adhesive film will not melt completely, which will reduce the bonding strength; if the temperature is too high, it may cause the adhesive film to age and decompose, which will also affect the bonding strength.

Pressure and time: Applying appropriate pressure can make the hot melt adhesive film fit closely with the adherend, expel air and enhance the contact effect. Curing time is also very important. Sufficient time allows the adhesive film to form a stable bonding structure during the cooling process, otherwise it will lead to insufficient bonding strength.

If you are eager to explore the bonding strength of hot melt adhesive film, please feel free to contact Weitao Plastic New Material. Our professional team is always ready to serve you at any time.