Plastic packaging and plastic packaging products account for an increasing share in the market, especially composite plastic flexible packaging, which has been widely used in food, medicine, chemical and other fields, among which food packaging accounts for the largest proportion, such as beverage packaging, quick-frozen food packaging, cooking food packaging, fast food packaging, etc., these products have brought great convenience to people's lives.
Types of Plastic Film
PVA Coated High Barrier Film
PVA-coated high-barrier film is made by coating PVA with added nano-inorganic substances on polyethylene film and then printing and compounding the cost-effectiveness of plastic film.
Under the premise of low cost, its barrier performance is not only significantly better than EVOH five-layer co-extrusion film, but also the packaging cost is also greatly reduced. The cost of aseptic packaging can be used to package beverages, juices, milk, soy sauce and vinegar, etc.
Biaxially Oriented Polypropylene Film (BOPP)
Biaxially oriented polypropylene film is made by co-extruding polypropylene particles to form a sheet, and then stretching in both vertical and horizontal directions. Due to the orientation of the stretched molecules, this film has good physical stability, mechanical strength, air tightness, high transparency and gloss, and is tough and wear-resistant. It is currently the most widely used printing film, and the general thickness is 20~ 40 μm, the most widely used is 20 μm. The main disadvantage of biaxially oriented polypropylene film is poor heat sealability, so it is generally used as the outer film of composite film. For example, after compounding with polyethylene film, the moisture resistance, transparency, strength, stiffness and printability are all ideal. Since the surface of the biaxially oriented polypropylene film is non-polar, with high crystallinity and low surface free energy, its printing performance is poor, and its adhesion to ink and adhesive is poor, and surface treatment is required before printing and compounding.
Low Density Polyethylene Film (LDPE)
Low-density polyethylene film is generally made by blow molding and casting. Cast polyethylene film has a uniform thickness, but due to its higher price and lower cost, it is the most widely used. Low-density polyethylene film is a translucent, glossy, soft film with excellent chemical stability, heat sealability, water resistance and moisture resistance, freezing resistance, and can be boiled. Its main disadvantage is that it has poor barrier properties to oxygen. It is often used as the inner film of composite flexible packaging materials, and it is also the most widely used and used plastic packaging film at present, accounting for more than 40% of the consumption of plastic packaging films.
Since polyethylene molecules do not contain polar groups, and have high crystallinity and low surface free energy, the printing performance of the film is poor, and the adhesion to ink and adhesive is poor, so it is necessary to carry out surface treatment before printing and compounding.
Polyester Film (PET)
Polyester film is a film material made of polyethylene terephthalate as a raw material, which is made into a thick sheet by extrusion and then biaxially stretched. It is a colorless, transparent, glossy film with excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high and low temperature resistance, chemical resistance, oil resistance, air tightness and fragrance retention. It is one of the commonly used barrier composite film substrates. However, the price of polyester film is relatively high, and its general thickness is 12 μ m. It is often used as the outer material of retort packaging, and its printing property is better.
Nylon Film (PA)
Nylon film is a very tough film with good transparency, good gloss, high tensile strength, high tensile strength, good heat resistance, cold resistance, oil resistance and organic solvent resistance, wear resistance, excellent resistance to puncture resistance, relatively soft, excellent oxygen barrier properties, but poor barrier properties to water vapor, high moisture absorption and moisture permeability, poor heat sealability, suitable for packaging hard items, such as greasy food, meat products, fried food, vacuum-packed food, steamed food, etc.
Cast Polypropylene Film (CPP)
Cast polypropylene film is a polypropylene film produced by casting process, which can be divided into ordinary CPP and cooking grade CPP. It has excellent transparency, uniform thickness, and uniform vertical and horizontal properties. The thickness of ordinary CPP film is generally between 25 and 50 μm. After compounding with OPP, the transparency is better, the surface is bright, and the hand feels firm. This material is used in general gift packaging bags. This film also has good heat sealability. The thickness of the cooking grade CPP film is generally between 60 and 80 μm, and it can withstand high-temperature cooking at 121°C for 30 minutes. It has good oil resistance, air tightness, and high heat-sealing strength. The inner layer of general meat packaging uses Retort grade CPP film.
At present, the most widely used aluminized films are polyester aluminized film (VMPET) and CPP aluminized film (VMCPP). The aluminized film has both the characteristics of a plastic film and the characteristics of a metal. The role of aluminum plating on the surface of the film is to shading and prevent ultraviolet radiation, which not only prolongs the shelf life of the contents, but also improves the brightness of the film. To a certain extent, it replaces aluminum foil, and it is also cheap, beautiful and good. Aluminized film is widely used in composite packaging.