First, polyvinylidene chloride: as a single-layer film, it can also be used in soft cans, and can be used as a packaging material for ham and sausage. Its sealing, ligation, heat shrinkage and gas barrier properties are excellent. Polyvinylidene chloride can also be used as a coating for nylon, polyester and other membrane materials. In addition, it is also used as a composite substrate for retort pouches, and is used on high-barrier polyvinylidene chloride films for high-temperature and high-pressure sterilization.
Second, polyester: has excellent transparency, heat resistance and abrasion resistance. Film thicknesses of 12 microns and 25 microns are printed on polyester, which can be used as lids for retort pouches or pans.
Third, high-density polyethylene: special high-density polyethylene for soft cans has been sold in Japan. Although this film has poor gas barrier properties, it can be used as a sealing layer due to its excellent tensile strength, elongation, tear strength and good sealing adaptability. However, high density polyethylene has several characteristics in terms of heat resistance, and its maximum heat resistance temperature is 120°C.
Fourth, polypropylene: it has good transparency, oil resistance, and heat resistance is better than special polyethylene, so it can be used as a sealing layer for cooking bags and cooking containers. Most of the sealing layers of soft can packaging materials are unstretched polypropylene films or sheets.
Fifth, aluminum foil: aluminum foil is made of electrolytic aluminum with a purity of more than 99% and is made by rolling. When used as a packaging material, aluminum foil is the only metal substrate in the packaging material. The thickness of aluminum foil used for retort pouches is 7-15 microns, and the thickness of aluminum foil used for retort containers is 50-130 microns. Because aluminum foil is non-toxic, odorless, has excellent shading properties, has extremely high moisture resistance, gas barrier properties and confidentiality, and can protect the packaged objects most effectively, it is the most suitable packaging material for fatty foods. However, due to the danger of pinholes occurring after bending the aluminum foil, it is necessary to use a plastic film as an outer layer to laminate it.
Sixth, nylon: It is indispensable as the base material of the packaging material for soft cans. There are two kinds of biaxial stretching and unstretching. Biaxially oriented nylon 6 film not only has excellent heat resistance and cold resistance, but also has good tear strength and pinhole resistance. Therefore, it can be used in combination with other raw materials. In addition, in order to prevent curling and improve strength, nylon 6-6 film is also used, but the price is higher than that of nylon 6.
