Blackening of aluminum coating in the process of t

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Blackening of aluminum coating during film printing

a color printing factory in Guangdong has received a batch of orders for jelly capping films to restore your work to normal. The material structure is pet printing//VMPET//PE (requires 80 ℃/20 min sterilization). The ink used is composite ink, which is compounded with our pu-1875 polyurethane adhesive. However, when the processed products are sterilized, the printed pattern color changes and slowly slows down, In particular, there is leakage at the junction of the printed pattern and the blank film (that is, the aluminum coating disappears). When another kind of glue is used for compounding, this phenomenon is reduced a lot. The manufacturer suspects that it is caused by the glue quality (not temperature resistant). Tongxinda company is in the industry leading position in the research and development of high-molecular composite materials related technology. Through the composite test, pu-1875 adhesive is used to prepare glue with different concentrations for composite. It is found that the connection container of the thinner composite is an evaporative condenser, and the degree of blackening is greater than that of the thicker one. The 321 polyester and nylon special inks of New Oriental company are used to print PET film, and then pu-1875 adhesives with different concentrations are used to composite the aluminized film. After the composite, both of them pass the sterilization of 90 ℃/20 min, and the composite film has no blackening phenomenon. Through this test, 4 ball mill friction tester: the friction pair is composed of 4 steel balls, and the reason for the blackening phenomenon lies in the printing ink

because vacuum aluminum plating is to evaporate and vaporize aluminum into aluminum vapor under high vacuum, and then coat it on the surface of the film to form a bright and dense aluminum layer. Most of the connecting materials of ordinary composite inks are chlorinated polypropylene and chlorinated EVA, which will partially decompose under high temperature, release hydrogen ions and chloride ions, and then react with Al to form aluminum chloride, and the aluminum layer will blacken and disappear. At the junction of the printed pattern and the blank, due to the thickness difference, the thickness of the adhesive layer will also be uneven, so the phenomenon is more obvious. In addition, a large amount of glue will also play a better barrier effect, and the blackening phenomenon will also be reduced

source: Zhejiang Huangyan Huaguang resin Co., Ltd. Author: xiaohaiyi

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