Views:2 Author:Vera Publish Time: 2018-09-26 Origin:Site
Special plastics for food packaging currently occupy the most important position in the field of food sales and packaging. It mainly includes PE, PP, PS, PET, PC, PVDC and so on.
Polyethylene is non-toxic and has excellent chemical resistance and low temperature resistance. It is easy to process.
In the field of food packaging, polyethylene is generally used as the inner layer material of fresh-keeping film, heat-shrinkage film or composite packaging film, and can also be used as the composite film and bag for packaging liquid food. At the same time can also blow molding, injection molding and other processing technology into containers, barrels and other packaging products.
Polypropylene is a nontoxic, odorless, highly crystallized polymer with a density of about 0.9g/cm3, which is one of the lightest varieties in the plastic. Polypropylene has two main categories of products in the field of food packaging: film and hollow products.
Compared with the conventional polypropylene film, the properties of the polypropylene film treated by directional tensile treatment are obviously improved. The strength of biaxially stretched polypropylene (BOPP) film is 8 times higher than that of ordinary film. It is used as the outer material of composite film, and the composite film has good moisture resistance, transparency, strength, stiffness and printing property, suitable for dry food. In addition, polypropylene can also be made into heat shrink film for food shrinkage packaging.
Polypropylene hollow products with good transparency, mechanical properties and gas barrier, are widely used in the field of food packaging. Polypropylene also has good high temperature resistance, is widely used in microwave heating plastic lunch box.
Polystyrene is a colorless, transparent and non-toxic packaging plastic for food. Polystyrene is easy to process and can be formed by conventional extrusion and injection molding. Polystyrene is widely used in the field of food packaging, such as plastic covers, boxes, cups, plates and so on. Polystyrene can be made into food boxes, bowls, trays and so on after it is foamed. Among them, foamed PS food boxes have caused great controversy, but at present most of the take-out box materials have become polypropylene or degradable materials. Polystyrene foamed plastic food boxes are more and more rare.
PET's most famous packaging products in the field of food are various beverage bottles, such as mineral water bottles. This is because PET can be made into colorless and transparent products, which have excellent barrier to water, gas, etc, and excellent weather resistance. PET can also be used to make transparent films for packaging greasy foods, or to make biaxially stretched heat shrinkage films; and used as heat-shrink packaging of meat or as a base material to make composite film for cooked food packaging and so on.
Polycarbonate is an amorphous, colorless and transparent plastic. It has good heat resistance and can be widely used under 120 ℃. Polycarbonate can be made into pots, bottles, cans and other high transparent food contact products. It has good toughness, durable and anti-fall, can withstand 100 ℃ high temperature sterilization treatment. Polycarbonate is also widely used in water cups. It has high transparency, beautiful appearance, light weight, impact resistance, not easy to deform, and very durable. However, due to the problem of bisphenol A, the application of polycarbonate in food industry has been controversial. It is generally believed that when using polycarbonate water cups, it is not appropriate to use them for hot water.
Polycarbonate can also be made into thin film by flow casting. This kind of film has strong oil resistance and can be used to make cooking food packaging bag by using its advantages of low permeability, water absorption and moisture absorption. Because of its good heat resistance, high strength, good fragrance performance, it can also be widely used in the manufacture of curry powder containers, pudding, fish chowder and other vacuum molding packaging.
Polyvinylidene chloride has the advantages of good flammability, corrosion resistance, air tightness, high barrier, etc. It is mainly used as casing for sausage or meat, cookies, vegetables and fruits and other food preservation packaging. The casing for sausage is the main application form of polyvinylidene chloride in the field of food packaging. PVDC has excellent barrier properties. It can preserve the moisture and original fragrance of food and prolong the shelf life of food. It is a kind of excellent food packaging material.
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