Quality Standard Of PVC Heat Shrinkable Film

July 20, 2017

PVC heat shrinkable film has the potential for development in culture and education, electrical appliances, medicine, food and other fields. Besides being used directly for packaging, it can be used for printing after corona treatment. In recent years, domestic PVC heat shrinkable film production equipment and raw materials have been introduced. More than 10 production lines have been put into operation. Let's see the following introduces of the PVC heat shrinkable film quality standard by the 

manufacturer. 

 

First,the thermal shrinkage test


The contraction film system is designed with the principle of polymer molecular chain stretching and orientating, and is formed by the method of cold pressing and setting. The physical principle is: when the polymer in high elastic state, the tensile orientation, then the following polymer quenched to glass transition temperature, molecular

orientation is frozen, when the goods in the packaging process of the heating, the stress relaxation due to thermal motion of molecules and molecules restore with the
original state, shrinkage. This property allows the heat shrinkable film to be smoothly attached to the beverage bottles of various shapes and to ensure smoothness and wrinkle free. Therefore, it is very important to test and control the thermal shrinkage of thin films. The method of measuring shrinkage can be referred to the following steps:

Cutting uniformly along the width direction of the film with 3 pcs specimen of 100 mm * 100 mm square which an edge parallel to the film longitudinal, and drawing a 

symmetrical axis on the longitudinal and transverse directions of the specimen, marked with longitudinal and transverse directions.Every time pick up one pc and put into the framework with two metal mesh (two mesh free shrinkage distance between 1 ~ 3 mm, should not affect the sample,and quickly immerse in 120 + 2 DEG C medium 

shrinkaging freely,20 s out, immersed in the spare bath at room temperature,and removed it out after 5 s' cooling,stay with flat and measure the vertical and horizontal axis of symmetry in 30 mins.Accurate to 1 mm, and record measurement data. The shrinkage ratio of the contraction film is calculated according to formula (1), and the contraction ratio of the shrink film is calculated according to formula (2).

 

Second,mechanical performance test


The mechanical properties of films are another important property of shrink films. In the beverage production process, labeling speed must keep up with the high speed filling speed, otherwise it will directly restrict the production speed, influence enterprise profit space, and excellent mechanical properties is the security of high speed and high quality labeling. The specific steps of mechanical performance test of heat shrinkable film are as follows: draw gently with the 10# sampling knife on the clean and smooth part of the film, and obtain a 10mm wide and suitable length sample to be tested.The upper and lower ends of specimen are clamped on the LabthinkPC type intelligent electronic tensile
testing machine (XLW (L) -500N) or intelligent electronic tensile testing machine (XLW-500N) on the chuck, and ensure the sample and tensile force measuring system in a straight line. Then, select the tensile strength or elongation at break test, and select the test speed of 500 mm/min, press the test key to test. The test of tearing performance is carried out according to QB/T 1130. The mechanical properties of heat shrinkable film should meet the requirements of the following table.

 

Project target requirement
                                                                    The thickness≤0.060mm  thickness>0.060mm

Tensile strength (longitudinal and transverse) Mpa        = 12                  = 12

Elongation (longitudinal and transverse)%                        = 200               = 250

Tear strength (vertical and horizontal) KN/m                   = 40                 = 40

 

Third,coefficient of friction test


In the beverage industry, single bottle packaging after usually with a certain amount of the overall package packaging, there will be a certain number of products in a transparent shrink film packaging materials by heat sealing in the form of packaging, the friction coefficient should not therefore requires a shrink film is too small. Excessive friction coefficient can not give the bottle wall proper resistance, so that it may cause the beverage bottle to fall off, and at the same time bring the trouble of production and transportation. Therefore, the proper coefficient of friction is a performance index that must be controlled during the beverage production process.

 

The test method is that the sample to be adhered to a square slide block with a side length of 63mm, and required that the prepared sample is smooth and wrinkle free. If the friction coefficient test film on the film, in need of friction coefficient tester (LabthinkMXD-01) of the test area for 8 cm * 20 cm flat specimen, then the slide block is arranged on the fixture, according to the test button to test the speed of 100 + 10 mm/min. If only the friction coefficient of the film to metal is tested, the slide block can be placed on the fixture directly and tested by the test key. The results can be printed through an embedded micro printer, or stored and printed by professional software and
communications lines. 

 

In addition to the above test items, the heat shrinkable film should be tested for thickness, heat sealing strength and other indicators. The applicable national standards are GB 6672 and GB/T 2358, and the applicable testing instruments are Labthink CHY-C1 high-precision measuring instrument, HST-H2 heat sealing tester, RTD-R1 heat sealing gradiometer and so on.

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