How to Choose Shrink Film? Standards for Identifying Shrink Film Quality.

2024-05-17 09:44:18 Zhejiang Zhongcheng Packing Material Co., Ltd Viewd 4
With the advancement of packaging technology, the requirements for various packaging materials are increasing. As an essential packaging material, shrink film has a wide range of qualities in the market, and one may inadvertently purchase inferior products. So, how should one choose shrink film? Below, we will introduce some tips.

During the normal operation of shrink packaging, the selection of shrink film material is crucial. Firstly, the film must have a certain shrinkage rate both longitudinally and transversely. The shrinkage rate is calculated as follows: shrinkage rate = (L1-L2)/L1 * 100%, where L1 is the original length, and L2 is the length after soaking in glycerin at 120°C for 1 to 2 seconds and cooled with water. Shrink film has the characteristic of thermal recovery. When the film is made from raw materials, it is preheated, stretched, and cooled to form the shrink film. When this film is reheated, it will shrink and return to its original shape.

Therefore, the film is required to have a shrinkage rate of about 50% in both vertical and horizontal directions, as well as sufficient heat sealing strength, tensile strength, impact strength, tear strength, appropriate moisture resistance, and oil resistance. There are many types of shrink films in use, such as Polyolefin (POF), Polyvinyl Chloride (PVC), Polyethylene (PE), Polypropylene (PP), followed by Polyvinylidene Chloride (PVDC), Polyester (PET), Polystyrene (EPS), Ethylene-Vinyl Acetate Copolymer (EVA).

The strength, transparency, and elongation of shrink film are superior to ordinary plastic films. When stretched at the appropriate temperature, the elongation of the film can increase to 1:4 to 1:7 before condensation, while the elongation of ordinary films is only 1:2. Shrink films are divided into two types, one is biaxially stretched shrink film, with almost equal axial stretching in the longitudinal and transverse directions.

National standards require shrink films to be tested for thickness, tensile properties, heat shrinkage rate, right-angle tear performance, and other physical properties. The corresponding testing instruments specified in the national standards include CHY-U Thickness Gauge for testing film thickness, XLW-500N Intelligent Electronic Tensile Testing Machine for testing tensile properties and right-angle tear performance, and RSY-03 Heat Shrinkage Tester for testing heat shrinkage rate. Strict compliance with national standard indicators is required for testing.

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