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The characteristics of aluminized film and its application in dry compounding (I)

aluminized film is a kind of composite flexible packaging material formed by coating a very thin layer of metal aluminum on the surface of plastic film by special process. Among them, the most commonly used processing method is vacuum evaporation method, which is to melt and evaporate metal aluminum at high temperature under high vacuum, so that the vapor precipitation of aluminum is accumulated on the surface of plastic film, Thus, the surface of the plastic film has metallic luster. Because it has the characteristics of both plastic film and metal, it is a kind of packaging material with low price, beautiful appearance, excellent performance and strong practicability. Therefore, aluminum coating has been widely used in the packaging of food, medicine, chemical products and other products, such as fast food, tea, coffee and cosmetics. This paper briefly introduces the characteristics of aluminized film and its application in dry compounding, with a total national production capacity of 1.13 billion tons in 2015

first, the characteristics and application of aluminized film

the use of aluminized film in flexible packaging mainly has the following outstanding advantages:

firstly, aluminized film composite products have the characteristics of plastic film; Secondly, a layer of dense "aluminum plating" on the surface has a good barrier effect; At the same time, it is also bright in appearance, thus beautifying the packaging effect of products; In addition, it replaces aluminum foil composite packaging to a certain extent, thereby reducing the packaging cost

(1) aluminized film has excellent metallic luster and good reflectivity, giving people a feeling of richness and luxury. Using it to package goods can beautify goods and improve the grade of goods

(2) aluminized film has excellent gas resistance, moisture resistance, light shielding and fragrance retention. It not only has strong barrier to oxygen and water vapor, but also can block almost all ultraviolet, visible light and infrared rays, and can prolong the storage life and shelf life of its contents. Therefore, for food, drugs and other products that need to extend the storage life, Using aluminized film as packaging is a quite good choice, which can prevent food or contents from corruption and deterioration due to moisture absorption, oxygen permeability, light exposure and other reasons. In addition, the aluminized film also has fragrance retention, and the fragrance transmission rate is small, which can keep the fragrance of the content for a long time. Therefore, aluminized film is an excellent barrier packaging material

(3) aluminized film can also replace aluminum foil to a certain extent, but the amount of aluminum is greatly reduced, which not only saves energy and materials, but also reduces the cost of commodity packaging

(4) the aluminized layer on the surface of the aluminized film has good conductivity and can eliminate the electrostatic effect. Therefore, the sealing performance is good, especially when packaging powdery goods, it can ensure the sealing of the packaging, thus greatly reducing the incidence of leakage

because of its outstanding advantages in the above aspects, the application of aluminum coating is becoming more and more so as to avoid being widely affected by experiments. It has become a very common packaging material in the flexible packaging industry. There are many kinds of aluminized films. At present, the most widely used aluminized films are polyester aluminized film (VMPET) and CPP aluminized film

(VMCPP). Polyester aluminized film (VMPET) is generally used as the middle layer of composite packaging. Because of its beautiful appearance, it is most used in high-end packaging, such as milk powder, tea and other packaging bags. CPP aluminized film (VMCPP) is generally used as the heat sealing layer of composite packaging, and is often used in the packaging of ordinary small food (such as biscuits)

II. Basic performance of aluminized film

1. Appearance. The surface of the aluminized film shall be flat and smooth, without wrinkles or only a small amount of flexible folds, without obvious bumps, obvious impurities and rigid blocks, without spots, bubbles, missing plating holes and other defects, and no obvious bright bars, yin and Yang surfaces and other phenomena are allowed

2. The thickness of aluminized film should be uniform, the horizontal and vertical thickness deviation is small, and the deviation distribution is relatively uniform. There are no obvious ribs on the drum, otherwise it is easy to wrinkle when compounding

3. Thickness of aluminum coating. The thickness of the aluminum coating is directly related to the barrier property of the aluminum coating. With the increase of the thickness of the aluminum coating, the transmittance of oxygen, water vapor, light, etc. gradually decreases, and accordingly, the barrier property of the aluminum coating is also improved. Therefore, the thickness of the aluminum coating should meet the standard requirements, and the coating should be uniform, otherwise the expected barrier effect will not be achieved

4. The aluminum coating has strong adhesion and good firmness, otherwise it is prone to dealumination, which will lead to quality problems. The lightweight body can not only be beneficial to the resistance problem of descending and climbing. During the processing of high-quality vacuum aluminizing film, a certain amount of primer should be coated on the aluminized surface of the aluminized substrate film first to improve the adhesion between the aluminized layer and the substrate film, so as to ensure that the aluminized layer is firm and not easy to fall off; Then, the aluminum coating should be coated with two-component polyurethane adhesive as the top coating to protect the aluminum coating from wear

5. Physical and mechanical properties. Because the aluminized film will be affected by mechanical force in the composite process, it is required to have certain mechanical strength and flexibility, and should have good tensile strength, elongation, tear strength, impact strength, excellent folding resistance and toughness, so as to ensure that it is not easy to appear kneading, folding, fracture and other phenomena in the composite processing process

6. Moisture permeability. Moisture permeability indicates the amount of water vapor transmission of aluminum coating under certain conditions, which reflects the moisture resistance of aluminum coating to a certain extent. For example, the moisture permeability of 12 um thick polyester aluminized film (VMPET) is between 0.3 g/M2 · 24h and 0.6 g/M2 · 24h (temperature 30 ℃, relative humidity 90%); The moisture permeability of CPP aluminized film (VMCPP) with a thickness of 25 um is 1 Compared with the aluminum chassis previously used, it is between 0 g/㎡ 24h and 1.5 g/㎡ 24h (temperature 30 ℃, relative humidity 90%)

7. Oxygen permeability. The oxygen permeability represents the oxygen permeability of the aluminized film under certain conditions, which reflects the resistance of the aluminized film to oxygen. For example, the oxygen permeability of the 25 um thick polyester aluminized film (VMPET) is about 1.24 ml/㎡ · 24h (temperature 23 ℃, relative humidity 90%)

8. The magnitude of surface tension. In order to make the printing ink and composite adhesive have good wettability and adhesion on the surface of aluminized film, it is required that the surface tension of aluminized film should reach a certain standard, otherwise the adhesion and adhesion of printing ink and adhesive on its surface will be affected, thus affecting the quality of printing and composite products. For example, the surface tension of polyester aluminized film (VMPET) is required to be more than 45 dynes, and at least more than 42 dynes

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