Source: Link Testing Instruments Co.,Ltd.
The friction coefficient is an important factor affecting the convenience of material use. Slippage, deviation, poor opening and other phenomena that occur during the use of packaging materials are all related to the inappropriate friction coefficient. Polyethylene shrink film is a common heat shrink film material. It is often used for the outer packaging of beer, beverages, wood, ceramics, electronic products, industrial products and other products. If the friction of the polyethylene shrink film is low, it will not interact with the above products. The sliding property is relatively large, and the product is prone to fall off. The obsolete 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 "Polyethylene Heat Shrinkable Film for Packaging" (2016 Implemented on November 1, 2019), the friction coefficient has been included in the examination of other properties of polyethylene shrink film. Although this standard does not make specific index requirements for the friction coefficient, it only stipulates that the supply and demand parties negotiate, but it does not require polyethylene shrinkage. Membranes put forward 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 methods and test equipment
GB/T 13519-2016 stipulates that the friction coefficient shall be tested in accordance with the requirements of GB 10006-1988 "Method for determination of friction coefficient of plastic films and sheets". GB10006 is suitable for non-adhesive plastic films and sheets with a thickness of less than 0.2mm on the surface of itself or other materials. Test of static friction coefficient and kinetic friction coefficient during sliding.
This test uses the LTCOF-05A friction coefficient meter to test the friction coefficient of the sample. This equipment is independently developed and produced by Link Testing Instruments Co.,Ltd.
Test principle: The friction coefficient is the ratio of the friction force between the 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 with a certain pressure, and the sample is tested at a set test speed. The friction coefficient of the sample can be obtained by the value of the tensile force when it slides relative to the friction surface.
Test samples and test procedure
Test sample:
The sample tested in this test is a polyethylene shrink film produced by a certain company, and the friction coefficient between the sample and glass is tested.
Test procedure:
(1) Cut three pieces of 8 cm × 20 cm samples from the polyethylene shrink film sample to be tested, and use the inner surface of the sample as the test surface. Do not touch the inner surface with your hands when cutting to ensure that the inner surface is not scratched, stained.
(2) Fix one of the specimens on the slider, with the outer surface in direct contact with the slider, and fix the glass plate for friction on the steel plate of the equipment. During the process of fixing the specimen and glass plate, do not touch the friction area with your hands.
(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 the test parameters such as test speed and test stroke, click the Start Test option, and the test starts.
(5) After the sample and the glass plate are in contact for 15 seconds, they start to move relative to each other. The equipment 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 two samples.
Test results and analysis
The friction coefficient of the polyethylene shrink film sample is the arithmetic average of the test results of the three samples. The static friction coefficient is 0.131 and the kinetic friction coefficient is 0.097.
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