Metallized film is a new type of composite flexible packaging material, in which the aluminized film is the most widely used one. In addition, gold, silver, copper, etc. can also be plated. A special process is used to apply a very thin layer of aluminum on the surface of the packaging plastic film or paper (single or double sided). Because the aluminum plating layer is relatively brittle and easily damaged, it is generally added with a layer of protective plastic film such as polyethylene, polyester, nylon and the like. The thickness of the aluminized layer is about 300 angstroms, which is thinner than aluminum foil. Aluminized films have many of the same excellent properties as aluminum foil composites:
1 Excellent barrier properties, long shelf life, suitable for packaging of foods, medicines, etc.
2 has a metallic luster, light reflectivity of up to 97%, so that goods to increase the sense of high-grade containers, increase the added value of goods.
3 Aluminum plating layer has good conductivity and can eliminate static electricity, so it has good sealing performance, especially when packaging powdered products, it will not contaminate the sealing part, guarantee the sealing of the packaging, and greatly reduce the leakage.
4 aluminum thickness can be arbitrarily chosen.
5 easy to print processing.
In addition to the same characteristics as above, aluminum-plated films have advantages over aluminum foil composites:
1 It has excellent folding endurance and good toughness, few pinholes and cracks, no soft cracking phenomenon, so the oxygen barrier is also more superior, which is sensitive to the packaging and easy to taste the food, and maintain the appearance Beauty is important.
The two parts of the film may not be plated so that the consumer can see the contents.
3 The aluminized layer is much thinner than the aluminum foil and therefore the cost is lower.
The comparison of the barrier properties of several commonly used aluminized films before and after aluminizing is shown in Table 14 (numbers in parentheses are the same thickness without aluminized films).
Table 14 Barrier properties before and after aluminizing of several commonly used aluminized films
Substrate
Indicator PET NY LDPE
Thickness (mm) 0.12 0.127 0.51
Moisture permeability (g/m2•24h) 0.78 (44.49) 3.1 (310) 0.45 (9.3)
Oxygen permeability (ml/m2•24h) 1.24(124) 0.78(46.5) 34.57(427.65)
The substrate (i.e., the carrier film) of the aluminized film is a plastic film and paper. The most commonly used plastic films are polyester (PET), nylon (NY), biaxially oriented polypropylene (BOPP), polyethylene (LDPE), and polyvinyl chloride (PVC). The first three kinds of aluminized films have excellent adhesion and gloss. It is a high performance aluminum plated composite material. Aluminized polyethylene film is popular due to its low price and good decor. Aluminized polypropylene film can also be made into easy-to-open seals for easy opening of pharmaceuticals. It is worth mentioning that the advantages of the aluminum-plated substrate are firstly that the cost is lower than that of the plastic film, and that it is thinner and cheaper than the aluminum foil/paper composite, and the performance is also comparable. Its processing performance is much better than that of aluminum foil/paper, for example, neat and tidy when die-cutting labels, and it is not easy to produce curls and creases in printing. Therefore, it has replaced aluminum foil in large quantities and become new-type commercial labels and decorating materials.
In view of the above advantages, the aluminized film is a new type of composite packaging material that is both successful and economical. In the past ten years, it has been widely used in Europe and the United States and other countries as well as China. It has replaced aluminum foil composite materials in many product packaging (for example, in the aspect of cigarette packaging, aluminum-plated paper is gradually replacing aluminum foil). Aluminized films are mainly used for vacuum packaging of foods such as snacks, snacks, meats, and agricultural products, as well as packaging and trademark materials for cigarettes, pharmaceuticals, alcohol, cosmetics, and the like.
(2) The relationship between thickness of aluminum plating and barrier properties
The barrier performance of the aluminized film is proportional to the aluminum metal being plated. That is, the greater the aluminizing amount, the thicker and the better the insulation performance. In addition, the barrier properties are also related to the substrate and require that the aluminum layer is minimally scratched during the compounding process. The amount of aluminum can be expressed by measuring the thickness or resistivity of the aluminum layer, or the optical density of the aluminized film. Abroad, the relevant information will be divided into thin and thick aluminum-plated film, optical density greater than 2.0 is thick. Thin type is generally used to package foods with a shelf life of less than 30 days; thick type is used to package moisture-absorbing foods, condiments and other sensitive foods. For example, the single-sided aluminum plating of a polyester film with a thickness of 0.012mm, the optical density is greater than 2.5, and the metal-coated side is compounded with 0.05mm thick low-density polyethylene, and the packaging material has a relatively stable less than 0.8ml/m2•24h. Oxygen permeability and moisture permeability of less than 0.8g/m2•24h and good opacity can enable shelf life of up to one year without the use of oxygen-free food additives.
Through experiments, the relationship between the optical density of the aluminum-plated film (ie, the thickness of the aluminum plating layer) and the moisture permeability, visible light transmittance, oxygen permeability, and ultraviolet transmittance was obtained. The experimental results show that with the increase of optical density (ie, the thickness of the aluminum plating layer), various transmittances are significantly decreased. The aluminum plating film with an optical density greater than 2.5 has excellent barrier properties.
1 Excellent barrier properties, long shelf life, suitable for packaging of foods, medicines, etc.
2 has a metallic luster, light reflectivity of up to 97%, so that goods to increase the sense of high-grade containers, increase the added value of goods.
3 Aluminum plating layer has good conductivity and can eliminate static electricity, so it has good sealing performance, especially when packaging powdered products, it will not contaminate the sealing part, guarantee the sealing of the packaging, and greatly reduce the leakage.
4 aluminum thickness can be arbitrarily chosen.
5 easy to print processing.
In addition to the same characteristics as above, aluminum-plated films have advantages over aluminum foil composites:
1 It has excellent folding endurance and good toughness, few pinholes and cracks, no soft cracking phenomenon, so the oxygen barrier is also more superior, which is sensitive to the packaging and easy to taste the food, and maintain the appearance Beauty is important.
The two parts of the film may not be plated so that the consumer can see the contents.
3 The aluminized layer is much thinner than the aluminum foil and therefore the cost is lower.
The comparison of the barrier properties of several commonly used aluminized films before and after aluminizing is shown in Table 14 (numbers in parentheses are the same thickness without aluminized films).
Table 14 Barrier properties before and after aluminizing of several commonly used aluminized films
Substrate
Indicator PET NY LDPE
Thickness (mm) 0.12 0.127 0.51
Moisture permeability (g/m2•24h) 0.78 (44.49) 3.1 (310) 0.45 (9.3)
Oxygen permeability (ml/m2•24h) 1.24(124) 0.78(46.5) 34.57(427.65)
The substrate (i.e., the carrier film) of the aluminized film is a plastic film and paper. The most commonly used plastic films are polyester (PET), nylon (NY), biaxially oriented polypropylene (BOPP), polyethylene (LDPE), and polyvinyl chloride (PVC). The first three kinds of aluminized films have excellent adhesion and gloss. It is a high performance aluminum plated composite material. Aluminized polyethylene film is popular due to its low price and good decor. Aluminized polypropylene film can also be made into easy-to-open seals for easy opening of pharmaceuticals. It is worth mentioning that the advantages of the aluminum-plated substrate are firstly that the cost is lower than that of the plastic film, and that it is thinner and cheaper than the aluminum foil/paper composite, and the performance is also comparable. Its processing performance is much better than that of aluminum foil/paper, for example, neat and tidy when die-cutting labels, and it is not easy to produce curls and creases in printing. Therefore, it has replaced aluminum foil in large quantities and become new-type commercial labels and decorating materials.
In view of the above advantages, the aluminized film is a new type of composite packaging material that is both successful and economical. In the past ten years, it has been widely used in Europe and the United States and other countries as well as China. It has replaced aluminum foil composite materials in many product packaging (for example, in the aspect of cigarette packaging, aluminum-plated paper is gradually replacing aluminum foil). Aluminized films are mainly used for vacuum packaging of foods such as snacks, snacks, meats, and agricultural products, as well as packaging and trademark materials for cigarettes, pharmaceuticals, alcohol, cosmetics, and the like.
(2) The relationship between thickness of aluminum plating and barrier properties
The barrier performance of the aluminized film is proportional to the aluminum metal being plated. That is, the greater the aluminizing amount, the thicker and the better the insulation performance. In addition, the barrier properties are also related to the substrate and require that the aluminum layer is minimally scratched during the compounding process. The amount of aluminum can be expressed by measuring the thickness or resistivity of the aluminum layer, or the optical density of the aluminized film. Abroad, the relevant information will be divided into thin and thick aluminum-plated film, optical density greater than 2.0 is thick. Thin type is generally used to package foods with a shelf life of less than 30 days; thick type is used to package moisture-absorbing foods, condiments and other sensitive foods. For example, the single-sided aluminum plating of a polyester film with a thickness of 0.012mm, the optical density is greater than 2.5, and the metal-coated side is compounded with 0.05mm thick low-density polyethylene, and the packaging material has a relatively stable less than 0.8ml/m2•24h. Oxygen permeability and moisture permeability of less than 0.8g/m2•24h and good opacity can enable shelf life of up to one year without the use of oxygen-free food additives.
Through experiments, the relationship between the optical density of the aluminum-plated film (ie, the thickness of the aluminum plating layer) and the moisture permeability, visible light transmittance, oxygen permeability, and ultraviolet transmittance was obtained. The experimental results show that with the increase of optical density (ie, the thickness of the aluminum plating layer), various transmittances are significantly decreased. The aluminum plating film with an optical density greater than 2.5 has excellent barrier properties.
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