biaxial polypropylene Film (BOPP)
Biaxially stretched polypropylene film is made by co-extruding polypropylene particles to form sheets, and then stretching in both vertical and horizontal directions. Due to the tensile molecular orientation, this film has good physical stability, mechanical strength, air tightness, high transparency and gloss, toughness and wear resistance, and is currently the most widely used printed film, generally using a thickness of 20 ~ 40μm, the most widely used for 20μm.
The main disadvantage of biaxial tensile polypropylene film is poor heat sealing, so it is generally used as the outer film of composite film, such as moisture resistance, transparency, strength, stiffness and printability after composite with polyethylene film are ideal, suitable for holding dry food.
Because the surface of the biaxial polypropylene film is non-polar, high crystallinity and low surface free energy, its printing performance is poor, and the adhesion to the ink and adhesive is poor, and surface treatment is required before printing and composite.
Low Density polyethylene Film (LDPE)
Low density polyethylene film is generally made by blow molding and casting process. The thickness of cast polyethylene film is uniform, but due to the high price, it is rarely used at present. Blow molded polyethylene film is made of blow molded PE particles by blow molding machine, low cost, so the most widely used. Low density polyethylene film is a translucent, shiny, soft film, with excellent chemical stability, heat sealing, water and moisture resistance, resistance to freezing, can be boiled.
Its main disadvantage is the poor barrier to oxygen, often used in the inner film of composite flexible packaging materials, but also the most widely used, the largest amount of a plastic packaging film, accounting for about 40% of the consumption of plastic packaging film.
Because the polyethylene molecule does not contain polar groups, and the crystallinity is high, the surface free energy is low, therefore, the printing performance of the film is poor, the adhesion to the ink and the adhesive is poor, so the surface treatment is needed before printing and composite.
Polyester film (PET)
Polyester film is made of polyethylene terephthalate as raw material, which is made into thick sheet by extrusion method and then made by bidirectional stretching.
It is a colorless transparent, glossy film, excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high temperature and low temperature resistance, chemical resistance, oil resistance, air tightness and good fragrance preservation, is one of the commonly used permeability resistance composite film substrate. However, the price of polyester film is higher, the general thickness is 12mm, and it is commonly used as the outer material of cooking packaging, and the printability is better.
Nylon Film (PA)
Nylon film is a very tough film, good transparency, and has good luster, tensile strength, tensile strength is high, but also has good heat resistance, cold resistance, oil resistance and organic solvent resistance, wear resistance, excellent puncture resistance, and relatively soft, excellent oxygen resistance, but the water vapor barrier is poor, moisture absorption, moisture permeability, heat sealing is poor. Suitable for packaging hard goods, such as greasy food, meat products, fried food, vacuum packaging food, cooking food, etc.
Cast polypropylene Film (CPP)
Casting polypropylene film is the polypropylene film produced by casting process, and can be divided into ordinary CPP and cooking grade CPP two kinds, excellent transparency, uniform thickness, and uniform vertical and horizontal performance, generally used as the inner layer of composite film material.
The thickness of ordinary CPP film is generally between 25 and 50μm, and the transparency of OPP composite is better, the surface is bright, and the feel is strong, and the general gift bags are made of this material. The film also has good heat sealing properties. The thickness of the cooking grade CPP film is generally between 60 and 80 μm, and it can cook at a high temperature of 121℃ and 30 min. It has good oil resistance, air tightness, and high heat sealing strength. The inner layer of the general meat packaging is made of cooking grade CPP film.
Aluminized film
At present, the most widely used aluminized films are polyester aluminized film (VMPET) and CPP aluminized film (VMCPP). The aluminized film has the characteristics of both plastic film and metal. The role of aluminum plating on the surface of the film is to block light and prevent ultraviolet radiation, which extends the shelf life of the contents and improves the brightness of the film, replaces aluminum foil to a certain extent, and also has cheap, beautiful and good barrier properties. Therefore, aluminum plating film is widely used in composite packaging. At present, it is mainly used in dry and puffed food packaging such as biscuits and some medicine and cosmetics.