How to choose shrink film? What is the quality identification standard of shrink film?
With the improvement of packaging technology at this stage, the requirements for various packaging materials are increasing. Shrink film is an essential packaging material for packaging. The quality of shrink film on the market is uneven at this stage. If you are not careful, you will buy inferior products. So how to choose shrink film? The following editor will introduce it to you.
In the normal working process of shrink packaging, the choice of shrink film material is very important. First of all, the film is required to have a certain shrinkage rate in the longitudinal and transverse directions, shrinkage rate = (L1-L2)/L1 * 100%, L1 is the original length, L2 is soaked in 120 glycerin for 1 ~ 2s, and cooled with water Shrink length. According to the heat recovery characteristics of shrink film, when the film is made of raw materials, it is pre-heated and stretched, and cooled to form a 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 the vertical and horizontal directions, and to have sufficient heat-sealing strength, tensile strength, impact strength, tear strength, appropriate moisture resistance and oil resistance, etc. There are many shrink films currently used, such as polyolefin heat shrinkable film (POF), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), followed by polyvinylidene chloride (PVDC), polyester ( PET), polystyrene (EPS), ethylene-vinyl acetate (EVA).
The strength, transparency and elongation of shrink film are superior to ordinary plastic films. Stretching at an appropriate temperature, the elongation of the film will increase to 1: 4 ~ 1: 7 before condensation, while the elongation of ordinary films is only 1: 2. Shrink film is divided into two types, one is biaxially stretched shrink film, and its longitudinal and transverse axial stretches are almost equal.
The national standard requires that the shrink film need to be tested for its thickness, tensile properties, thermal shrinkage rate, right-angle tearing properties and other physical tests. The national standard also points out the testing instruments needed for its physical indicators: CHY-U thickness gauge to test the thickness of the film; XLW-500N intelligent electronic tensile machine to test its tensile properties and right-angle tear properties; RSY-03 thermal The shrinkage tester tests its heat shrinkage. It is required to strictly follow the national standard indicators for testing.