The reason of aluminum transfer is that the bonding force between the aluminum coating and the substrate is less than that between the aluminum coating and the glue layer, which leads to the decrease of the overall peeling strength of the composite film, resulting in the phenomenon that a large number of aluminum plating layers leave the substrate and migrate to the glue layer.
At present, VMCPP and VMPET are the most commonly used aluminizing films, while OPP / VMCPP, PET / VMCPP and PET / VMPET are the corresponding composite film structures. In practical applications, PET / VMPET composite is the most prone to problems, because it is often used in the intermediate composite. This is because CPP and pet are very different in tensile properties as the base material of aluminum plating. The rigidity of pet is relatively large. Once it is compounded with materials with great rigidity, the adhesion of aluminum coating is easily damaged due to the existence of cohesive force during the curing process of adhesive, thus causing the migration of aluminum coating.
Main reasons and treatment methods:
(1) Too much glue. The amount of glue should be appropriate. If the amount of glue is too small, it will undoubtedly cause the composite fastness to be smaller and easy to peel off; but too large amount of glue will lead to volatilization and false drying. Secondly, the amount of coating glue is large, the curing time is long, and the penetration of aluminum coating is strong. Therefore, it should be based on the substrate and use, after a small test to determine the reasonable process parameters, choose a reasonable amount of glue.
(2) The main reason is that the curing temperature is too high. Controlling the curing time and reducing the curing temperature can reduce the transfer of aluminum plating.
(3) Glue mix proportion is not correct. Reducing the proportion of curing agent in a certain range can improve the transfer of aluminum plating. The specific method is to reduce the amount of curing agent when mixing the working glue solution, so as to reduce the crosslinking reaction degree between the main agent and the curing agent, thus reducing the brittleness of the adhesive film, maintaining good flexibility and extensibility, so as to control the transfer of aluminum coating.
(4) Adhesive selection is not correct. Choose suitable or special adhesive. In the composite aluminum coating, do not use the adhesive with low viscosity, because the low viscosity adhesive has small molecular weight, weak intermolecular force and strong molecular activity, which is easy to penetrate into the aluminum plating and affect the adhesion ability of aluminum plating.
(5) The quality of the substrate itself is poor. Change the suitable substrate.
(6) If the operation tension is too high, the aluminum coating will be strained, resulting in elastic change and transfer. The tension must be well controlled during the unwinding of aluminum plating. The reason is that the aluminized film will stretch under tension and produce elastic deformation. The aluminum coating is easy to loosen and the adhesion is reduced.
(7) Residual solvent will destroy the aluminum plating. Because the aluminum coating of the aluminum film is relatively thin, it is inevitable that there will be some pinholes, and the residual solvent will penetrate into the aluminum coating to destroy the aluminum layer, resulting in the transfer of aluminum
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, a world famous manufacturing city, is a subsidiary company of Beite packaging (China) Co., Ltd
With an area of 6000 square meters, it is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of advanced production equipment in China
We provide customers with high-quality products and first-class service with the support of the humanized management system and a group of experienced technical personnel.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for food, daily chemicals, and other special-shaped bags
Electronic, toys, medicine, cosmetics, industrial products and other industries of internal and external packaging.
We uphold the integrity of cooperation, good quality, thoughtful service business philosophy, the industry's recognition, products sold all over the world; welcome to call friends from all walks of life
Consulting, visiting our factory for investigation and guidance and business negotiation.