With the improvement of packaging technology, the requirements for various packaging materials are increasing day by day. Shrink film as a necessary packaging material, the quality of shrink film on the market at this stage is uneven, not careful will buy inferior products, so how to choose shrink film? The following Xiaobian will introduce to you.

In the normal process of shrink packaging, the choice of shrink film material is very important. First, the film is required to have a certain shrinkage rate in both longitudinal and transverse, shrinkage rate =(L1-L2)/L1 * 100%, L1 is the original length, L2 is the shrinkage length after soaking in 120 glycerol for 1 ~ 2s and cooling with water. According to the shrink-film property of heat recovery, when the film is made from raw materials, it is pre-heated and stretched, cooled to form a shrink-film, and when this film is reheated, it will shrink and return to its original state.

Therefore, the film is required to have a shrinkage rate of about 50% in the vertical and horizontal directions, and has sufficient heat sealing strength, tensile strength, impact strength, tear strength, appropriate moisture resistance and oil resistance. At present, many shrink films are used, such as polyolefin heat shrink film (POF), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), followed by polyvinylidene ethylene (PVDC), polyester (PET), polystyrene (EPS), vinyl acetate copolymer (EVA).

The strength, transparency and elongation of shrink film are better than that of ordinary plastic film. When stretched at the appropriate temperature, the elongation of the film will be increased to 1: 4 ~ 1: 7 before condensation, while the elongation of the ordinary film is only 1: 2. Shrink film is divided into two kinds, one is bidirectional stretch film, its longitudinal and transverse axial stretch is almost equal.

The national standard requires the shrinkage film to be tested for its thickness, tensile property, thermal shrinkage rate, right Angle tearing property and other physical tests. The national standard also points out that the physical indicators need to be used in the testing instrument: CHY-U thickness tester to test the thickness of the film; XLW-500N intelligent electronic tension machine to test the tensile property and right Angle tearing property; RSY-03 thermal shrinkage tester was used to test its thermal shrinkage rate. Requirements should be strictly in accordance with the national standard index detection.