Common difference and the types of the protective film

1, low density polyethylene protective film ( LDPE） : low density polyethylene blow molding commonly used protective film and stretch film two process. Stretch film PE protective film of uniform thickness, but because the price is higher, now rarely used. Blow molding polyethylene film is made by blow molding grade PE particles by blow molding machine blowing, and the cost is low, so the most widely used. Low density polyethylene film is a translucent, luster, texture is soft membrane, it has excellent chemical stability, heat sealing, water resistance and moisture resistance, freezing resistance, can be boiled. Its main drawback is that of oxygen barrier property is bad, often used in the inner membrane of composite flexible packaging material, and is currently the most widely used, the dosage is one of the biggest plastic packaging film, more than about 40% of plastic packaging film consumption. Because of the polyethylene molecules that do not contain polar groups, and high crystallinity, surface free energy is low, therefore, the protective film in the printing performance is poorer, to the poor adhesion of inks and adhesives, so the need for surface treatment before printing and composite. 2, two-way stretching polypropylene protective film ( BOPP) : two-way stretch polypropylene protection film is formed by polypropylene granules by co-extrusion sheets, then through vertical and horizontal directions made by stretching. Due to stretching molecular orientation, so the film physical stability, mechanical strength, good air tightness, high transparency and gloss, tough wear-resisting, is currently the most widely used printing film, generally use thickness is 20 ~ 40 microns, and the most widely used for 20 microns. Two-way stretch polypropylene film main drawback is that poor heat sealing, so generally used as the outer membrane of composite membrane, such as with polyethylene film composite after moisture resistance, transparency, strength, stiffness and printing are ideal, suitable for holding food drying. As a result of the two-way stretch polypropylene film surface for non-polar, high crystallinity, surface free energy is low, therefore, the printing performance is poorer, to the poor adhesion of inks and adhesives, the need for surface treatment before printing and composite. 3, pet protective film, PET) : polyester coating based on polyethylene terephthalate as raw material, adopt legal system into thick slices, then through two-way stretch protective film material. It is a colorless, transparent, glossy film, good mechanical properties, high rigidity, hardness and toughness, durability, friction resistance, high temperature and low temperature resistance, chemical resistance, oil resistance, good air tightness and sweet, is one of the permeability resistance of composite film base material. But the polyester film price is higher, the general thickness is 12 mm, the outer layer of the commonly used for cooking and packaging materials, printing is better. 4, cast polypropylene protective film ( CPP) : stretch the production of polypropylene protective film is a stretch of polypropylene protective film, and can be divided into ordinary CPP and CPP two level cooking, excellent transparency, uniform thickness, and the performance of the lateral uniform, generally used as the lining of the composite film material. Common CPP film thickness between 25 ~ 50 microns, and after the OPP composite has good transparency, surface light, feel is strong, gift bags are commonly used this kind of material. The film also has good heat sealing. Cooking class of CPP film thickness, generally between 60 to 80 microns, which can withstand temperatures up to 121 ℃, 30 min cooking, oil resistance, good air tightness and heat sealing strength is high, the general meat packaging inner cooking level adopts the CPP film.