Aluminum Plating Migration and Film Additive Problems

The composite flexible packaging material has developed rapidly in recent years. Due to its variety of varieties and comprehensive performance advantages, it has become more and more widely used in food, medicine, daily-use chemical, and other fields, and the involved substrates are also covered. Paper, aluminum foil and all kinds of plastic films are very large. In this paper, some simple discussions are made on the problems that occur during the use of aluminum-plated films and polyethylene films (CPE).
1. Aluminum Plating Migration Problems Aluminum plating is a new material that has emerged in recent years. It not only has the characteristics of a plastic film, but also replaces aluminum foil to some extent, and it plays a role in improving product quality, and it is relatively cost-effective. Lower, so it is widely used in the packaging of biscuits and snack foods. However, in the production process, the problem of transfer of the aluminized layer often occurs, resulting in a decrease in the peel strength of the layered film of the composite film, degrading the product performance, and seriously affecting the quality of the contents of the package.
At present, the most used aluminized film is CPP aluminized PET aluminum film. The corresponding composite film structure includes OPP/CPP aluminum plating, PET/CPP aluminum plating, and PET/PET aluminum. In practical applications, the most problematic issue is PET composite aluminum plating. The reason for the analysis is mainly as a substrate for aluminum plating. CPP and PET have a large difference in tensile properties. PET has a large rigidity, and once it is compounded with a material that also has a very high rigidity, it is cured in a film. During the process, due to the presence of cohesive force, it is easy to cause damage to the adhesion of the aluminum plating layer, so that the aluminum plating layer migrates. In addition, the penetration of the glue itself has a certain influence on it. In this regard, in the operation of the composite process, the following aspects must be noted:
(1) Choose the right adhesive. In the composite aluminized film, be careful not to use an adhesive with a low viscosity, because the low-viscosity adhesive has a small molecular weight and weak interaction force between molecules, so that the activity of the molecules is relatively strong, and the aluminum plating layer that easily penetrates through the film is destroyed. The strength of its attachment to the substrate.
(2) enhance the flexibility of the film. The specific method is to reduce the amount of curing agent in the working glue, so that the degree of cross-linking reaction of the main agent and the curing agent is reduced, thereby reducing the brittleness of the film, so that it maintains good flexibility and stretchability , It is conducive to control the transfer of aluminum plating.
(3) The amount of glue should be appropriate. If the amount of glue is too small, it will undoubtedly result in less composite fastness and easy peeling. However, if the amount of glue is too large, it is not good. First, it is uneconomical. Second, the amount of glue that is applied is large and the curing time is long. The osmosis of the layer is strong. So you should choose a reasonable amount of glue.
(4) Control the tension. When aluminum is unwound, the tension must be controlled and not too large. The reason is that the aluminized film stretches under tension and causes elastic deformation. The aluminum plating layer is accordingly easily loosened and the adhesion is relatively reduced.
(5) Curing speed. In principle, the aging temperature should be increased and the curing speed should be increased, so that the adhesive molecules can be quickly cured and the permeation and destruction effects can be reduced.
2. Precipitation of additives in CPE films The additives mentioned here mainly refer to lubricants used in the production of CPE films, especially external lubricants. Most of them are low-melting waxes that tend to precipitate on the surface of the film. Practice shows that when the thickness of CPE film exceeds 60μ, the phenomenon of precipitation of additives will be greatly increased. This is because with the same specific surface area, as the film thickness increases, the amount of additives contained inside it also increases accordingly, and thus the precipitation occurs. The possibility also increases. What is the effect of the precipitation of nitrocellulose on the composite membrane? The most important thing is that it will create a barrier layer, which greatly weakens the composite strength, especially at the edge of the seal, making it easy for weapons and separation. Some manufacturers often encounter such problems when producing vacuum bags and rice bags. To solve the problem of additive precipitation, there are the following points in the process:
(1) Film surface treatment. In addition to the film manufacturer's own control, the user must confirm that the surface tension of the CPE film fully meets the requirements. If necessary, EDM treatment may even be performed again because the precipitated wax can be volatilized and removed under the high temperature of EDM.
(2) Select the right adhesive. From the adhesive point of view, it is necessary to enhance the tolerance of the glue to additive precipitates and minimize their impact.
(3) Curing control. Unlike the aluminized film, aging should be performed at a low temperature as much as possible in order to prevent the high temperature from intensifying the precipitation.