Plastic packaging and plastic packaging products account for a growing share of the market, specifically for flexible plastic packaging, which has been widely used in food, medicine, chemical and other fields. In this case, food packaging accounts for the largest proportion, like beverages. Packaging, quick-frozen food packaging, retort food packaging, fast food packaging, etc., these products have brought great convenience to people's survival.
Several common films
1. Biaxially oriented polypropylene film (BOPP)
The biaxially oriented polypropylene film is obtained by coextruding polypropylene particles into sheets and then stretching them in two directions. Because of the orientation of the stretched molecules, the film has good physical stability, mechanical strength, air tightness, high transparency and brilliance, and is strong and wearable. It is the most popular printing film currently used, and the thickness is usually 20~. 40 μm, the most common application is 20 μm. The disadvantage of the tension of the biaxially stretched polypropylene film is that the heat sealability is poor, so that the outer film which is usually used as a composite film, such as moisture resistance, transparency, strength, stiffness and printability after being combined with the polyethylene film, is ideal. Contains dry foods. Because the appearance of the biaxially oriented polypropylene film is non-polar, the crystallinity is high, and the freeness of the appearance is low, the printing performance is poor, the adhesion to the ink and the adhesive is poor, and the appearance is necessary before printing and compounding. Processing.
2. Low density polyethylene film (LDPE)
Low density polyethylene films are typically made by both blow molding and casting processes. The thickness of the cast polyethylene film is symmetrical, but it is currently rarely used because of its high cost. Blown polyethylene film is blown from blown grade PE pellets by a blow molding machine at a lower cost, so it is most commonly used. Low-density polyethylene film is a translucent, radiant, soft-textured film with excellent chemical stability, heat sealability, water resistance and moisture resistance, freeze-resistant and boilable. The shortcoming is that it is poorly isolated from oxygen. It is often used in the inner film of composite flexible packaging materials. It is also the most common and most used plastic packaging film in current applications, 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 free energy of the appearance is low. Therefore, the printing performance of the film is poor, and the adhesion to the ink and the adhesive is poor, so it is necessary before printing and compounding. Hold the appearance of punishment.
3, polyester film (PET)
The polyester film is thus made of polyethylene terephthalate as a material, and is formed into a film material which is formed into a thick sheet by extrusion and then biaxially stretched. It is a colorless, transparent, radiant film with excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high temperature resistance, low chemical resistance, oil resistance, air tightness and aroma retention. Good, it is one of the commonly used barrier composite film substrates. However, the polyester film has a high cost, usually 12 mm in thickness, and is commonly used as an outer layer material for retort packaging, and has good printability.
4, nylon film (PA)
Nylon film is a very strong film with good transparency, good light, high tensile strength, high tensile strength, good heat resistance, cold resistance, oil resistance and organic solvent resistance. Excellent wear resistance and puncture resistance, softness and excellent oxygen barrier, but poorly isolated from water vapor, high moisture absorption and moisture permeability, poor heat sealability, suitable for packaging hard articles, such as Greasy foods, meat products, fried foods, vacuum-packed foods, cooked foods, etc.
5. Cast polypropylene film (CPP)
The cast polypropylene film is a polypropylene film which is produced by the casting process. It can be divided into ordinary CPP and cooking grade CPP. It has excellent transparency, uniform thickness, and uniform longitudinal and lateral properties. It is usually used as a composite film. Layer material. The thickness of the ordinary CPP film is usually between 25 and 50 μm. After compounding with OPP, the transparency is better, the appearance is bright and the hand feels firm, and the usual gift bags receive the material. This film also has good heat sealability. The cooking grade CPP film is usually between 60 and 80 μm thick. It can withstand high temperature cooking at 121 ° C for 30 min. It has good oil resistance and air tightness and high heat seal strength. The inner layer of the meat package is usually A CPP film of the cooking grade is accepted.
6, aluminized film
The most widely used aluminized films are polyester aluminized film (VMPET) and CPP aluminized film (VMCPP). The aluminized film has both the properties of a plastic film and the properties of a metal. The role of aluminum plating on the appearance of the film is to prevent light and ultraviolet radiation, which not only extends the shelf life of the content, but also increases the brightness of the film. It replaces the aluminum foil with a certain degree of certainty, and also has low cost, good elegance and good insulation performance. Therefore, the application of aluminized film in composite packaging is very common, and it is currently applied to dry, puffed food packaging such as biscuits and some outer packagings of medicines and cosmetics.