Source: Link Testing Instruments Co.,Ltd.
The coefficient of friction is an important factor affecting the convenience of use of materials. The phenomena of slipping, deviation, and poor opening of packaging materials during the use of packaging materials are all related to the inappropriate coefficient of friction. Polyethylene shrink film is a common heat-shrinkable film material. It is often used for the outer packaging of beer, beverages, wood, ceramics, electronic products, industrial products, etc. If the friction of polyethylene shrink film is low, the sliding property is relatively large, and the product is prone to fall off. The voided national standard for polyethylene shrink film GB/T 13519-1992 "Polyethylene heat shrinkable film" does not involve friction coefficient, and its replacement standard GB/T 13519-2016 "Packaging polyethylene heat shrinkable film" (2016 Implemented on November 1, 2011), the friction coefficient was included in the investigation of other properties of polyethylene shrink film. Although the standard did not make specific index requirements for the friction coefficient, it only stipulated that it should be negotiated between the supply and demand sides, but the polyethylene shrink film Membranes have higher requirements. Therefore, the detection and control of the friction coefficient of polyethylene shrink film is an effective way to improve its performance, and it is also a basic requirement of the standard.
Test method and test Instrument
GB/T 13519-2016 stipulates that the coefficient of friction shall be tested in accordance with the requirements of GB 10006-1988 "Methods for Determination of Coefficient of Friction of Plastic Films and Sheets". The test of the coefficient of static friction and the coefficient of dynamic friction when sliding.
This test uses the LTCOF-05A friction coefficient instrument to test the friction coefficient of the sample. This instrument is independently developed and produced by Link Testing Instruments Co., Ltd.
Test principle: The friction coefficient is the ratio of the friction force between two contact surfaces to the vertical force acting on one of the surfaces. In this test, a slider of a certain specification is applied to the sample to a certain pressure, and the test sample is tested at a set test speed. The friction coefficient of the sample can be obtained by the force value when sliding relative to the friction surface.
Test sample and test process
The sample tested in this test is a polyethylene shrink film produced by a certain company, and the coefficient of friction between the sample and glass is tested.
(1) Cut 3 samples of 8 cm × 20 cm from the polyethylene shrink film sample to be tested, and use the inner surface of the sample as the test surface. When cutting the sample, do not touch the inner surface with your hands to ensure that the inner surface does not Scratched, polluted.
(2) One of the samples is fixed on the slider, the outer surface is in direct contact with the slider, and the glass plate for friction is fixed on the steel plate of the instrument. During the process of fixing the sample and the glass plate, the friction area should not be touched by hand.
(3) Place the slider in the middle area of the glass plate without impact to ensure that the force measuring system is not stressed.
(4) Set test parameters such as test speed, test stroke, etc., click the option to start the test, and the test starts.
(5) After the sample is in contact with the flat sample surface for 15s, it starts to move relative to each other. The instrument automatically records the force value changes during the test and calculates the test results.
(6) Repeat the sample loading-click test process to test the dynamic and static friction coefficients of the remaining 2 samples.
Test Results and Analysis
The friction coefficient of the polyethylene shrink film sample is the arithmetic mean of the test results of three samples, the static friction coefficient is 0.131, and the dynamic friction coefficient is 0.097.
The coefficient of friction is an important factor affecting the packaging effect and performance of polyethylene shrink film, and the new version of GB/T 13519-2016 adds the detection requirements for the coefficient of friction of polyethylene shrink film. Judging from the test process of the friction coefficient between the polyethylene shrink film sample and the glass plate in this paper, the test is simple, the instrument is easy to operate, and can accurately reflect the friction coefficient of the polyethylene shrink film. The selected friction surface is different, and the friction coefficient measured by the same sample is different. Therefore, when testing the friction coefficient of polyethylene shrink film, the friction surface should be reasonably selected according to the different contact products. In addition, during the sample preparation process, the friction area of the sample should also be prevented from being polluted to ensure the accuracy of the test results.
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