1. Moisture resistance: it is the property of blocking the penetration of water vapor. When the film molecules do not contain hydrophilic hydroxyl and carboxyl groups, it is considered to have good moisture resistance. The moisture resistance changes greatly with the temperature. The moisture resistance of the film is suitable for all meat products packaging. If the product moisture penetrates from the inside of the packaging film in the form of water vapor, or the product absorbs the water vapor from the outside, the flavor, organization and content of the product will also change, especially for the packaging of dry sausages with little moisture and quantitative meat products to prevent natural loss.
2. Oxygen resistance: it is the property of isolating oxygen transmission. Not only oxygen, but also other gases. The amount of gas passing through the plastic film has no headlines with the molecular size of the gas. Usually, it is carried out in two steps. At first, the gas is dissolved in the molecules of the film, and then infiltrated through diffusion. The oxygen resistance of the film is applicable to the packaging of all meat products except raw meat. Especially in vacuum packaging and inflatable packaging. Due to the role of oxygen, hemoglobin is changed into high iron heme, causing product discoloration, promoting fat oxidation and the proliferation of aerobic microorganisms. Therefore, preventing the product from contacting with oxygen is very important for maintaining product quality and improving preservation.
3. Shading: this property has a great impact on vacuum packaged sliced meat products, colored meat mouth and smoked meat products. The transparent film has no effect of shielding ultraviolet rays. Although HDPE has some shading, the film is opaque. There are many methods to prevent ultraviolet transmission, one of which is to use the nature of light to block light. This method uses printing ink to absorb or reflect light, or uses Satin processing roller to mechanically extrude concave convex patterns on the film surface to reflect light.
4. Cold resistance: at low temperature, the film will not become brittle and can still maintain its strength and impact resistance. Some low-temperature meat products must be stored and sold under low temperature conditions, while some meat products must be stored under frozen conditions. Therefore, the packaging film of the product must be able to withstand low temperature, and the low-temperature resistance of the packaging film also affects the sealing strength.
5. Heat resistance: it refers to the property of high softening point and no deformation even after heating. Since the product expands during heating, the heat-resistant strength of the film must be guaranteed.
6. Impact resistance: this property is applicable to all kinds of packaging. The impact resistance of packaging materials can be ensured by the balance of tensile strength, tensile strength and impact.
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