Aluminum foil usually refers to aluminum materials with a purity of more than 99.5% and a thickness of less than 0.2 mm. The thickness of aluminum foil used for composite materials will be thinner. Of course, different countries have different requirements for the thickness and composition of aluminum foil.
However, in food packaging practice, aluminum foil is rarely used alone because aluminum foil itself has some shortcomings. For example, as aluminum foil is further thinned, the number of pores will increase, which will affect the barrier properties of the aluminum foil. At the same time, thin and flexible aluminum foil has limitations in resistance to stretch and shear, and generally cannot be used for structural packaging. Fortunately, aluminum foil has good secondary processing properties. Aluminum foil can usually be combined with other packaging materials to make composite packaging materials to make up for the shortcomings of aluminum foil, thereby improving the comprehensive packaging performance of composite packaging materials.
We usually call a film composed of two or more materials a composite film, and a packaging bag made of a composite film is called a composite film bag. In general, plastics, aluminum foil, paper and other materials can be made into composite films by bonding or heat sealing methods to meet the different packaging needs of a variety of foods. In modern packaging, almost all composite materials that require opacity and high barrier properties use aluminum foil as the barrier layer. This is because aluminum foil has a highly dense metal crystal structure and has good barrier properties against any gas.
In food flexible packaging, there is a packaging material called "vacuum aluminized film". Is it the same thing as aluminum foil composite packaging material? Although both contain a thin layer of aluminum, they are not the same material. Vacuum aluminum plating film uses evaporation method to attach high-purity aluminum to plastic film under vacuum, while aluminum foil composite material combines aluminum foil with other materials through bonding or heat sealing.
Different from aluminum foil composite materials, the aluminum-plated layer in the aluminum-plated film does not have the blocking effect of aluminum foil. It is the base film itself that plays the blocking role. Since the aluminum-plated layer is much thinner than aluminum foil, the cost of aluminum-plated film is lower than that of aluminum foil composite materials. Its application market is also very wide, but it is generally not used for vacuum packaging.
