Preservative film is a kind of plastic packaging products, which is mainly used in heating microwave food, preserving refrigerator food, fresh and cooked food packaging and other occasions. According to the different materials, the preservative film can be divided into the following types, which are suitable for different occasions.
The first film is polyethylene (PE),which is usually a mixture of similar polymers of ethylene. As the most common plastic in use today, it is primarily used for food packaging (fruits, vegetables and semi-finished cooked food sold in supermarkets).
The second is PVC, which can also be used in food packaging, but it has certain harm to the health. It is also used in making bottles, non-food packaging, food-covering sheets, and cards (such as bank or membership cards)
The last one is polyvinylidene chloride (PVDC) - a homopolymer of vinylidene chloride, which is mainly used for the packaging of cooked food, ham and other products.
Among the three kinds of fresh-keeping films, PE and PVDC are health and can be used safely, while PVC is harmful to human body because it contains carcinogens. Therefore, PE is the first choice when choosing fresh-keeping film. In general, the more higher the barrier property of the material is, the better the preservation of fresh food is.
Gas Permeability Coefficient (P), also known as Gas Permeability, is the volume of gas passed through unit thickness and area of the sample in unit time under constant temperature and unit pressure. GPT-201B Gas Permeability Tester is based on the differential pressure method and is professionally applicable to the determination of gas transmission rate as well as solubility coefficient, diffusion coefficient and permeability coefficient of plastic films, composite films, high barrier materials, sheeting, metal foils, rubber, tires and permeable membranes.
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