Performance comparison of several high barrier materials
BY：Industry news
CLICK：468
POST：2021-05-31
In recent years, the development of high barrier composite materials is a worldwide trend. At present, the high barrier materials in the market include aluminum foil, PVDC, EVOH coextrusion film, nylon composite film, vacuum plating SiOx film, etc. Among the above high barrier materials, aluminum foil composite film and nylon composite film are widely used in the field of flexible packaging.
Aluminum foil composite film is used as flexible packaging material, which has the advantages of high barrier performance, metallic luster, beautiful packaging effect and high temperature sterilization resistance at 121 ℃. But there are also some shortcomings: (1) the price is high: the thickness of aluminum foil in the composite film is 9 ~ 14 μ m. If it is too thin, there will be obvious pinholes, making barrier failure, and if it is too thick, the cost and price will be on the high side（ 2) Opaque: the real content can not be seen, which is contrary to consumers' consciousness and affects the sales of products（ 3) With vacuum bag, the aluminum foil will break and crack when the material is wrinkled, so that the barrier will be lost（ 4) It cannot be used for microwave heating.
Nylon composite film, EVOH coextrusion film, PVDC composite film and vacuum coated SiOx film overcome the shortcomings of aluminum foil, such as non transparent and non microwave heating. Compared with aluminum foil, nylon composite film has the advantages of low price, good transparency, softness, strong puncture resistance and poor barrier performance (see Table 3). After sterilization at 121 ℃ for 30 min, the shelf life of meat products packed in nylon cooking bags was only 2-3 weeks at room temperature, and shorter at higher temperature in summer; In addition, nylon material is a kind of hydrophilic polymer, which turns white after moisture absorption with water and steam, and its transparency and barrier properties decrease rapidly. Meat products packaged with nylon material are generally refrigerated at low temperature, and rarely stored at room temperature.
At present, there is no production of SiOx film in China. It has a common characteristic with PVDC coating film, vacuum aluminum coating film and a series of films produced by coating and evaporation methods, that is, the adhesion between coating layer and its film is limited, the coating layer is thin, and the coating is easy to crack or fall off under cooking, which makes the barrier loss. Therefore, although the resistance rate is high, it is not used for the packaging of contents that need cooking.
EVOH coextrusion film, because EVOH plastic itself has excellent gas barrier, but because it is a hydrolysate, the molecule contains a large number of hydrophilic groups, has strong hydrophilicity, absorbs water and steam, and turns white. When the ambient humidity exceeds 60% RH, its barrier performance drops sharply, and its barrier performance to water vapor is poor; In addition, EVOH coextrusion film can withstand temperature below 100 ℃. Therefore, EVOH can not be used for the packaging of products that need high temperature sterilization at 121 ℃, and it is not suitable for the packaging of products with high water content (see Figure 2).
In contrast, compared with aluminum foil, PVDC composite film is cheap, transparent, helpful for product display, and can be heated by microwave; Compared with nylon, the oxygen permeability and water vapor permeability of PVDC composite membrane are 1 / 10 ~ 1 / 5 of nylon, and do not change greatly with ambient temperature and humidity. After high temperature and high pressure sterilization, the shelf life of the packaged meat products can reach more than 6 months at room temperature; Compared with EVOH, PVDC laminated composite film can be used for packaging of high temperature cooking products, and the barrier rate changes little with humidity and temperature.
To sum up, PVDC is an excellent food packaging material, especially resistant to high temperature cooking and good barrier to oxygen, steam and various odors, which is incomparable with other plastics. Therefore, we have reason to believe that: with the development of food industry and the emergence of new packaging technology and packaging methods, PVDC laminated composite film is more and more popular in the field of food packaging, and because of its excellent performance, it will be widely used in food, medicine, chemical industry and other fields.
Aluminum foil composite film is used as flexible packaging material, which has the advantages of high barrier performance, metallic luster, beautiful packaging effect and high temperature sterilization resistance at 121 ℃. But there are also some shortcomings: (1) the price is high: the thickness of aluminum foil in the composite film is 9 ~ 14 μ m. If it is too thin, there will be obvious pinholes, making barrier failure, and if it is too thick, the cost and price will be on the high side（ 2) Opaque: the real content can not be seen, which is contrary to consumers' consciousness and affects the sales of products（ 3) With vacuum bag, the aluminum foil will break and crack when the material is wrinkled, so that the barrier will be lost（ 4) It cannot be used for microwave heating.
Nylon composite film, EVOH coextrusion film, PVDC composite film and vacuum coated SiOx film overcome the shortcomings of aluminum foil, such as non transparent and non microwave heating. Compared with aluminum foil, nylon composite film has the advantages of low price, good transparency, softness, strong puncture resistance and poor barrier performance (see Table 3). After sterilization at 121 ℃ for 30 min, the shelf life of meat products packed in nylon cooking bags was only 2-3 weeks at room temperature, and shorter at higher temperature in summer; In addition, nylon material is a kind of hydrophilic polymer, which turns white after moisture absorption with water and steam, and its transparency and barrier properties decrease rapidly. Meat products packaged with nylon material are generally refrigerated at low temperature, and rarely stored at room temperature.
At present, there is no production of SiOx film in China. It has a common characteristic with PVDC coating film, vacuum aluminum coating film and a series of films produced by coating and evaporation methods, that is, the adhesion between coating layer and its film is limited, the coating layer is thin, and the coating is easy to crack or fall off under cooking, which makes the barrier loss. Therefore, although the resistance rate is high, it is not used for the packaging of contents that need cooking.
EVOH coextrusion film, because EVOH plastic itself has excellent gas barrier, but because it is a hydrolysate, the molecule contains a large number of hydrophilic groups, has strong hydrophilicity, absorbs water and steam, and turns white. When the ambient humidity exceeds 60% RH, its barrier performance drops sharply, and its barrier performance to water vapor is poor; In addition, EVOH coextrusion film can withstand temperature below 100 ℃. Therefore, EVOH can not be used for the packaging of products that need high temperature sterilization at 121 ℃, and it is not suitable for the packaging of products with high water content (see Figure 2).
In contrast, compared with aluminum foil, PVDC composite film is cheap, transparent, helpful for product display, and can be heated by microwave; Compared with nylon, the oxygen permeability and water vapor permeability of PVDC composite membrane are 1 / 10 ~ 1 / 5 of nylon, and do not change greatly with ambient temperature and humidity. After high temperature and high pressure sterilization, the shelf life of the packaged meat products can reach more than 6 months at room temperature; Compared with EVOH, PVDC laminated composite film can be used for packaging of high temperature cooking products, and the barrier rate changes little with humidity and temperature.
To sum up, PVDC is an excellent food packaging material, especially resistant to high temperature cooking and good barrier to oxygen, steam and various odors, which is incomparable with other plastics. Therefore, we have reason to believe that: with the development of food industry and the emergence of new packaging technology and packaging methods, PVDC laminated composite film is more and more popular in the field of food packaging, and because of its excellent performance, it will be widely used in food, medicine, chemical industry and other fields.