Composite packaging bag peel strength is always low? This is how to solve it

The low peel strength of composite packaging bags is usually caused by several factors: excessive proportion of release agents and opening agents in the materials, unqualified corona treatment, poor ink adhesion, ink consumption of curing agents, and transfer of the aluminum layer of the aluminum-plated film. Based on these reasons, Shunxingyuan Packaging, a professional flexible packaging manufacturer, shares its production experience to explain how high-quality composite packaging bags are produced.

1. Surface Tension Test

Testing the surface tension of the film is essential. For polar materials such as PET or BOPA, due to the high surface tension of the film surface itself, good composite strength can be achieved even without corona treatment. However, BOPP film is a non-polar material and its surface tension does not meet the requirements for lamination; therefore, corona treatment must be performed on the lamination surface. In addition, the surface tension gradually decreases with time and environmental changes. Therefore, for non-polar materials, the surface tension must be tested before use, especially for materials that have been stored for a long time.

2. Reasonable Control of Adhesive Application

The control of adhesive application is crucial in the lamination process. Generally, considering production costs, the adhesive application in the actual production process is usually controlled below the theoretical requirement. However, the adhesive application process cannot remain unchanged and needs to be adjusted according to the film type and thickness. Generally, ordinary composite materials are controlled at 2.0g/㎡～2.5g/㎡. For products laminated with aluminum foil, the adhesive application should be controlled at 3.5g/㎡ or more. For materials with a heat-sealing layer thickness of more than 60μ, especially when the amount of opening release agent is high, the adhesive application should be appropriately increased, usually controlled at 3.0g/㎡. For materials that need to be sterilized, since the peel strength needs to reach 5N/15mm or more, the adhesive application needs to be controlled at 4.5g/㎡ or more.

3. Choose Stable Suppliers

Whether it is film substrate, ink, or adhesive, well-known domestic and international suppliers should be chosen. These manufacturers have advanced production and testing equipment, stable production processes, and strong technical support, making their product quality more reliable than some small manufacturers.

4. Process Control for Aluminum-Plated Products

1. Control Adhesive Application

On the premise of ensuring the appearance of the composite, the adhesive application should not be too high, generally controlled between 2.0g/㎡～2.5g/㎡, because excessive coating will cause the composite film to harden and cause the aluminum layer to transfer.

2. Use Special Aluminum-Plated Composite Adhesive

Adhesive manufacturers have developed specific adhesives for the characteristics of aluminum-plated films. These adhesives have smaller molecular weights and can penetrate the pinholes in the aluminum layer to produce higher bonding force between the aluminum layer and the film.

5. Control Curing Temperature and Time

When determining the curing process for aluminum-plated composite materials, considering the factor of inner material shrinkage damaging the aluminum layer, the curing temperature is lower than that of general products, and the curing time needs to be strictly controlled. Generally, the curing temperature is controlled at around 40℃, and the curing time is controlled at 36 hours. In environments with higher temperatures, room temperature curing can be considered.

6. Control the Amount of Curing Agent

After sufficient testing, the proportion of adhesive curing agent can be appropriately reduced, generally by 5%. However, this method is not recommended for films printed with full-coverage polyurethane ink, because the hydroxyl groups in the ink will consume the curing agent, resulting in incomplete curing of the adhesive, uneven ends after slitting, or adhesive extrusion, seriously affecting product quality.