1. Biaxially oriented polypropylene film (BOPP) The biaxially oriented polypropylene film is obtained by coextruding polypropylene particles into sheets and then stretching them in both directions. Due to the orientation of the stretched molecules, the film has good physical stability, mechanical strength, air tightness, high transparency and gloss, and is tough and wear resistant. It is the most widely used printing film at present, and the thickness is generally 20~ 40 μm, the most widely used is 20 μm. The main disadvantage of the biaxially oriented polypropylene film is that it has poor heat sealability, so it is generally used as an outer film of a composite film. For example, it is ideal for moisture resistance, transparency, strength, stiffness and printability after being combined with a polyethylene film. Contains dry food. Since the surface of the biaxially oriented polypropylene film is non-polar, the crystallinity is high, and the surface free energy is low, the printing performance is poor, the adhesion to the ink and the adhesive is poor, and the surface is required before printing and compounding. deal with. Zhongsu Online Plastic Encyclopedia http://baike.21cp.com
2. Low Density Polyethylene Film (LDPE) Low density polyethylene film is generally produced by two processes of blow molding and casting. The thickness of the cast polyethylene film is uniform, but it is rarely used because of its high price. Blow-blown polyethylene film is blown from blow molding PE particles by a blow molding machine, and has a lower cost, so it is the most widely used. Low-density polyethylene film is a translucent, shiny, soft-textured film with excellent chemical stability, heat-sealing, water resistance and moisture resistance, freeze-resistant and boilable. Its main disadvantage is its poor barrier to oxygen. It is commonly used in the inner film of composite flexible packaging materials. It is also the most widely used and widely used plastic packaging film, accounting for more than 40% of the consumption of plastic packaging film. . Since the polyethylene molecule does not contain a polar group and has high crystallinity and low surface free energy, the film has poor printing performance and poor adhesion to inks and adhesives, so it is required before printing and compounding. Surface treatment.
3, polyester film (PET)
The polyester film is a film material made of polyethylene terephthalate as a raw material, formed into a thick sheet by extrusion, and then biaxially stretched. It is a colorless, transparent and lustrous film with 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 aroma retention. Good, it is one of the commonly used barrier composite film substrates. However, the price of the polyester film is relatively high, generally 12 mm in thickness, and is commonly used as an outer layer material for retort packaging, and has good printability.
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