Main plastic film substrates for composite films

(1) Polyethylene film is mainly used as the inner substrate of the composite film, or as the coating layer for the composite film. The coating layer is extruded and the inner layer of the composite film is co extruded. As mentioned in Chapter 2 earlier, as the density of polyethylene resin increases, the strength and barrier properties of the film increase, and the heat resistance is good. Polyethylene with the same density has different properties due to different preparation methods. Moreover, the manufacturing methods of thin films vary, and their performance also varies. Polyethylene film has sufficient sources and low cost, making it a commonly used substrate that does not require heat resistance.

(2) Polypropylene cast film has high strength, uniform thickness, good heat sealing performance, and good heat resistance. It is mostly used for the inner layer of composite films, especially suitable for high-temperature cooking bags.

In the production of extruded coating films and co extruded composite films, polypropylene films have good heat sealing properties and high temperature resistance, and are used as inner layers in extruded coating films and co extruded composite films.

(3) Biaxially stretched polypropylene film is one of the widely used substrates for composite films. It has high mechanical properties, good transparency and luster, high usage temperature, low relative density, and high utilization rate. It is usually used as the outer layer of a composite film, and combined with aluminum foil, a film with oxygen barrier properties, and an inner layer with good heat sealing properties to make a composite film with high barrier properties.

(4) Biaxially stretched polyester film is also one of the widely used substrates. As a packaging material, it has extremely high mechanical properties, good firmness, medium gas resistance, excellent drug resistance, excellent transparency and glossiness, good fragrance retention, and good printability. It is widely used as the outer layer of composite films for refrigerated and frozen food packaging, steaming and sterilization packaging, high-speed automatic packaging, cosmetics packaging, and water containing packaging.

(5) Biaxially stretched nylon film is one of the commonly used composite film substrates. It has excellent toughness, heat and cold resistance, needle hole resistance, bending and cracking resistance, wear resistance, good gas barrier, and good glossiness. It is used as the surface or intermediate layer of composite films, and composite films are used for vacuum packaging, inflatable packaging, liquid packaging, cooking and sterilization packaging, etc.

(6) Polyvinylidene chloride film is a high barrier substrate film. It has excellent gas barrier and water vapor barrier properties, and is used as the most commonly used barrier material in composite films, as an intermediate layer of composite films, or as a coating method to further reduce costs.