Abstract: Peeling force is to evaluate the composite film peeling performance indicators, the size of the value reflects the composition of the composite film monolayer membrane composite fastness. Low peeling force of composite film materials, after making the contents of the bag packaging is prone to delamination phenomenon, resulting in composite film impact resistance, puncture resistance and other physical and mechanical properties and barrier properties decline, affecting the appearance and quality of the product. In this paper, we use the GBH-2 electronic tensile testing machine independently developed by Guangzhou Standard International to carry out the peeling test of composite film for pickles packaging, introduce the test standard, test equipment, test process, etc., and effectively evaluate the anti-interlayer peeling performance of composite film for pickles packaging.

Pickled vegetables is a general term for a variety of vegetable products made from vegetables as the main raw materials and using different pickling techniques. According to the process and auxiliary materials, pickles can be divided into soy sauce, salt pickles, soy sauce pickles, sugar pickles, vinegar pickles, sweet and sour pickles, shrimp oil pickles, brine pickles, bad pickles and so on. Due to the unique aroma of sweet and crispy pickles, or salty and spicy pickles, and their nutritional value, they have won the favour of the masses and have become one of the most popular foodstuffs to accompany meals.

Bagging is a common packaging form of pickles, the bag material is mainly plastic composite film, aluminium composite film, etc., generally using vacuum packaging form to prevent pickles rancidity. In the actual use of the process, some pickles finished packaging will appear composite film delamination phenomenon. If the adhesive used in the composite film and the ink used in the external printing of the package is of poor quality and not resistant to high temperature or acid or alkali, it is easy to cause the composite film to reduce the composite fastness of each single layer of the film and the composite film is prone to delamination after high-temperature sterilisation or contact with the acid or alkali components in pickles. On the other hand, if the composite film using the adhesive coating amount is too low or too thick, or uneven coating, will also cause the composite film between the layers of film composite fastness is poor, easy to occur delamination. Once the phenomenon of delamination occurs, the bag composite film impact resistance, puncture resistance and other physical and mechanical properties will decline, resulting in easy rupture of the bag, leakage; at the same time will also affect the composite film on the outside world of oxygen barrier properties, resulting in an increase in the amount of oxygen through the packaging contents are prone to deterioration, flavour, and seriously affect the appearance of the product and product quality. Therefore, the anti-interlayer peeling performance (composite fastness) of composite film is one of the important parameters for evaluating the quality of composite film. In this paper, we use the GBH-2 electronic tensile tester independently developed by GBPI to carry out the peeling test of composite film for pickles packaging.

1.Testing Standards

GB 8808-1988 Peel Test Method for Soft Composite Plastic Materials

2. Testing Instruments

This equipment is a mechanical performance testing machine developed and manufactured by Guangzhou Standard R&D team based on the requirements of GB, JIS, ASTM, DIN and other standards and market demands. The instrument adopts high-precision transducer, force measurement accuracy within ± 0.5 %FS; high-precision ball screw loading, loading smooth, long life of the test machine; professional software support, fully automatic operation, equipped with a colour touch screen, real-time display of the test curve data and can query the test report, the test is convenient; fixture application diversification, can be customized according to the customer's scenarios test requirements fixtures; and has a perfect At the same time, it has perfect limit protection, overload protection, automatic return to the emergency stop and other safety protection functions. Applicable to a variety of metal, non-metallic materials, such as tensile, peeling, heat sealing, tearing, puncture, compression, bending, shear and other tests, can also be used in the medical industry, syringe piston sliding, body tightness and other test verification.
3.Testing Principle
Fix the treated specimen between the two collets of the fixture, start the instrument to make the two collets do relative movement, the force sensor located in the movable collet collects the change of force value during the test, the displacement sensor built-in the machine collects the change of displacement, so as to calculate the specimen's performance indexes of tensile, tearing, peeling, deformation rate and so on.

4.Test samples
Sample of laminated film for pickle packaging provided by a customer.

1, specimen preparation:
(1) the use of sample cutter along the bag composite film, longitudinal and transverse, respectively, cut the width of 15.0mm, 200mm long specimen each of the 5, the composite film composite direction for the longitudinal direction.
(2) At one end of the specimen, along the length of the specimen will be composite layer and the substrate pre-peeled 50mm (the peeled part shall not have obvious damage).
2, open the equipment host switch and test software, click on the main interface of the specimen type settings, select [peeling], and then enter the parameter setting interface to set the parameters required for the peeling test, set the scale distance, test speed, specimen width and other parameters.
3、 Install the fixture on the tensile machine, clamp the two ends of the peeling part of the specimen on the upper and lower fixtures, so that the longitudinal axis of the peeling part of the specimen and the upper and lower fixture centre line coincides with the appropriate tightening and loosening of the specimen clamping schematic diagram is as follows:
Picture
4、 Click on the test start option, the specimen starts, the instrument automatically measures the force changes during the peeling process of the specimen, and automatically displays the test results after the test is finished.
5、 Replace the specimen, carry out the next test, after all the 5 specimens have been tested, export the test result report, the instrument automatically calculates the average peeling force of the specimen and displays it in the report.
5. Test results

The transverse peeling force of the laminated film for pickle packaging in this test was 5.57 N/15mm, 5.70 N/15mm, 5.60 N/15mm, 5.30 N/15mm and 5.55 N/15mm;
The mean value of 5 specimens was 5.54 N/15mm;
The longitudinal peeling forces were 5.83 N/15mm, 5.58 N/15mm, 5.76 N/15mm, 5.53 N/15mm, 5.76 N/15mm;
The average value of 5 specimens was 5.70 N/15mm.
6. Conclusion

Peeling force is one of the important physical and mechanical performance indexes for evaluating the quality of sauces packaging and other soft-plastic composite packaging.GBH-2 electronic tensile tester can easily realise the peeling test of composite film materials with high test accuracy, good data repeatability, simple operation, etc., and it can truly respond to the composite fastness of the composite film materials, providing reliable data support for the related enterprises. In addition to tensile, peeling, heat sealing, tearing, puncture, compression, bending, shear and other basic mechanical tests, the equipment can also be used for the mechanical properties of the pharmaceutical packaging materials (plastic, metal, pre-filled sealing class) test, a wide range of applications, superior performance, is a good choice for mechanical properties test.