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What is “initial bonding strength of adhesive” and what are the influence factors?

 

The “initial bonding strength” or “initial adhesion force” of adhesive is an important factor when evaluating the performance of the lamination products.  What is it? 


Table of contents:

1. Introduction.

2. Factors Affecting Initial Adhesive Strength

3. Strategies for Enhancing Initial Adhesive Strength

4. Further Reading: Additional Resources for Adhesive Composite Manufacturing


I. Introduction

The “initial bonding strength” or “initial adhesion force” of adhesive refers to the interlayer peel strength of the laminated film that has just come off the machine. For the vast majority of solvent-free lamination products, the initial bonding strength is in the range of 0.2 ~ 0.4N/15mm. For most solvent-based lamination products with a solid content of 75%, the initial adhesion force is in the range of 0.5 ~ 1.5N/15mm. For most solvent-based lamination products with a solid content of 50%, the initial bonding strength is above 1.5N/15mm.

II. Factors Affecting Initial Adhesion Force

In general, the initial adhesion force of lamination products is related to the molecular weight of the original adhesive. The larger the molecular weight of the original adhesive, the higher the initial bonding strength of the  lamination product. Typically, the lower the solid content of the original adhesive, the larger its molecular weight.

 

III. Strategies for Enhancing Initial Bonding Strength

The initial bonding strength of the lamination products is not only related to the nature of the adhesive but also influenced to some extent by the laminating processing technology. As mentioned earlier, the molecular weight of the original adhesive has a direct impact on the initial adhesion force. Therefore, during the lamination processing, any measures that can promote cross-linking reactions between the main agent and curing agent in the mixed adhesive contribute to improving the initial adhesive strength of lamination products. 

These measures include:

1. Allowing the prepared solvent-based lamination adhesive to stand for a period of time.

2. Increasing the temperature of the drying oven (raising the surface temperature of the freshly carrier film).

3. Raising the temperature of the nip unit.

4. Reducing the laminating processing rate (effectively increasing the temperature of the drying oven and the nip unit).

5. Increasing the temperature of the bearing roller/metering roller (solvent-free dry lamination process).

IV. Further Reading

Additional Resources for Adhesive Composite Manufacturing

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