Fabrication of the hottest vacuum aluminized film

2022-08-20
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Production of vacuum aluminized films and solutions to common problems

vacuum aluminized films such as VMPET (polyester aluminized), vmbopp (biaxially oriented polypropylene aluminized), VMCPP (cast polypropylene aluminized), vmcpe (polyethylene aluminized), vmpvc (polyvinyl chloride aluminized) are widely used in food, medicine, seeds, pesticides, communications, electronics Packaging materials for chemical and military industries. With the development and application of new technologies, aluminized films and their extension materials, such as kvmpet, kvmbopp, vmpvc, integrate high barrier, sanitary, tasteless, economic, environmental protection and other functions, and are increasingly favored by the market and industry insiders. They develop new production technologies, which are known as a wonderful flower of soft packaging materials. This paper discusses the manufacturing process, quality inspection and solutions to common quality problems of aluminized film, as well as the precautions in the storage, transportation and use of aluminized film with flexible packaging colleagues

I. manufacturing process

vacuum aluminum plating is to heat and melt aluminum metal to evaporation under vacuum, and aluminum atoms condense on the surface of polymer materials to form an extremely thin aluminum layer

1. requirements for substrate

vacuum aluminum plating requires that the surface of the substrate be clean, smooth, flat and uniform in thickness; Stiffness and friction coefficient are appropriate; The surface wetting tension is greater than 38dyn/cm; It has good thermal performance and can withstand the heat radiation and condensation heat of the evaporation source; The moisture content of the substrate is less than 0.1%

2. Requirements for equipment

the limit vacuum degree of the vacuum system is required to reach PA, and it works continuously to extract the gas released by the membrane roll; Vacuum pumping time is less than 20min; The tension of winding and unwinding is constant; The working temperature of the cooling system is in the range of -15~35 ℃, and the cooling time is small, with a history of 510 years and 25min; The film is rolled smoothly

3. Process requirements

the vacuum degree shall not be lower than PA to avoid brown stripes or uneven thickness of aluminum layer; Control the system tension. Turn on the cooling system to avoid thermal deformation of the film; Match the coiling speed (200~350m/min) and aluminum feeding speed (0.4~1.0m/min ф 2mm aluminum wire) and evaporation boat heating current to obtain the required aluminum layer thickness. A certain amount of primer such as polyacrylic resin can be coated on the film in advance, which can be fully dried and then vacuum aluminized to improve the thickness of the aluminum layer and the adhesion between the film and the aluminum layer

II 4.2.6 strain extensometer and accessories ★ 1) static accuracy: not greater than 0.5% of the indicated value; ★ 2) dynamic accuracy: no more than 1% of the indicated value; 3) Gauge length: 25mm; 4) Strain limitation: 10% detection of aluminized film and solutions to common quality problems

1. Appearance requirements of aluminized film

aluminum layer is uniform and bright, without water marks and clouds; The number of pinholes shall not exceed 0.5/m2; The coiling shall be smooth and the tension shall be appropriate, without serious stretching and reinforcement burst. The physical machinery, such as water vapor transmission and oxygen transmission, adopts different test methods according to different films and whether they have heat sealing performance. The thickness of the aluminum layer of the aluminized film is expressed by the square resistance or calculated directly according to gb/t "vacuum metal coating thickness test method, resistance, and finally the result of the experiment is displayed or printed out"

2. solutions to common quality problems

① brown stripes appear on the film surface

cause: a low vacuum degree

solution: clean the aluminum feeding, evaporation device, cooling system, unwinding, coiling device and guide roller in the vacuum chamber; Check the vacuum system; Reduce ambient humidity

b film releases gas

solution: film pre drying; Extend the vacuum pumping time

c too much aluminum spraying

solution: increase the speed; Reduce evaporation boat current; Reduce the aluminum feeding speed

d there are impurities in the evaporation boat

solution: clean the evaporation boat and heat shield plate e the evaporation boat is aging

solution: replace the evaporation boat

② holes appear in the film during aluminum plating

cause: a the aluminum material in the evaporation boat is too full

solution: reduce the aluminum feeding speed; Increase the evaporation boat current

b there is a short circuit between the evaporation boats in the vacuum chamber

solution: eliminate the short circuit

c impurity splashing in the vacuum chamber

solution: clean the wall of the vacuum chamber, send aluminum evaporation device, cool the drum, unwind, take-up device and all guide rollers

③ film stretching during aluminum plating

cause: a the tension of substrate is too large

solution: adjust the unwinding and coiling tension control system to reduce the tension appropriately

b the cooling system works abnormally

solution: check the cooling system and eliminate the fault

c the temperature of the evaporation boat is too high

solution: reduce the heating current of the evaporation boat and increase the speed

III. precautions during storage, transportation and use

the aluminum layer on the surface of aluminum plated film is very susceptible to moisture or water oxidation, so the relative humidity of the environment should be controlled during rewinding to prevent water vapor from being drawn into the film. It should be packed tightly and stored in a clean, cool and dry environment. Prevent rain and sunshine during transportation. During printing and drying, the environmental humidity should be well controlled, especially in the humid and rainy southern region. The unpacked film roll should be used up at one time to prevent moisture, oxidation and deterioration

with the continuous progress of vacuum coating technology in China and the development of coating equipment in the direction of wide width, high efficiency, low energy consumption and environmental protection, aluminized film and its extension materials are highlighting their competitive advantages with high performance and low cost, bringing new vitality to the flexible packaging market; At the same time, it shows that continuous optimization of the value chain with technological progress and the implementation of low-cost differentiation strategy are the magic weapons for flexible packaging enterprises to win the market

(author/Yang Hulin, Zhang Husheng)

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