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Overview of flexible packaging inspection and control technology (II)

III. The measurement of friction coefficient of flexible plastic packaging materials

can control and adjust the opening of packaging bags, packaging speed of packaging machines and other production quality process indicators. The friction coefficient test is suitable for non viscous plastic films and thin sheets with a thickness of less than 0.2

test methods are discussed as follows

1 sample and its preparation

1.1 sample size

1.1.1 two 8cm are generally required for each measurement × 20cm sample

1.1.2 if the sample is thick or rigid, and double-sided tape must be used to fix it to the slider, the size of one sample shall be the same as the bottom size of the slider (60 mm × 63mm)

2.2 cutting of sample

the sample shall be cut evenly in the whole width or circumference of the sample (in case of pipe film)

2.3 face and direction of the sample

if the friction properties of the front and back sides of the sample or different directions are different, the test shall be carried out separately. In general, the length direction (i.e. test direction) of the specimen shall be parallel to the longitudinal direction (machining direction) of the specimen

2.4 requirements for samples and test surfaces

2.4.1 the samples shall be flat, free of wrinkles and scars that may change the friction properties. The edge of the specimen shall be smooth

2.4.2 the test surface of the sample shall be free of dust, fingerprints and any foreign substances that may change the surface properties

2.5 number of samples, at least three pairs of samples shall be measured for each test. If higher test accuracy is required, the number of samples can be increased

3 condition adjustment of samples and standard environment for test

condition adjustment of samples shall be conducted for at least 16h under the standard environment with temperature of 23 ± 21 ° C and relative humidity of 45%-55%. Then the test shall be carried out under the same environment

4 test steps (equipment: electronic tensile machine ldm-100, Beijing landmark)

4.1 determination of film (sheet) to film (sheet)

4.1.1 the test surface of a sample shall be upward and smoothly fixed on the horizontal test bench. The length direction of the specimen and the test bench shall be parallel

4.1.2 place the test surface of another sample downward, wrap the slider, and fix the sample on the front and upper surfaces of the slider with adhesive tape

4.1.3 if the specimen is thick or rigid, which may produce bending moment and uneven pressure distribution, the 63mm specified in 1.1.2 shall be used × 63mm specimen. Fix the sample with double-sided tape between the bottom of the slider and the non test surface of the sample

4.1.4 computer: it is used to collect and analyze data. 4 place the slider fixed with the sample in the center of the first sample without impact, and make the test direction of the two samples parallel to the sliding direction, and the force measuring system is just not under force

then start the test

after the two samples are kept in contact for 15s, the two samples move relatively, and the first peak of the force is the static friction FS

the average value of the force within 6cm of the relative movement of the two samples (excluding the static friction) is the dynamic friction FD. This process is automatically controlled

4.1.5 during the test, if the force value oscillates after the static friction, the dynamic friction cannot be measured. At this time, the spring between the sliding block and the load sensor shall be canceled, and the dynamic friction shall be measured separately. Due to inertia error, this measurement is not applicable to static friction

4.1.6 when the friction coefficient of the measured object is less than 0.006, it is recommended to use the 500g slider configured by Beijing landmaker equipment for accuracy

5 test results show that

5.1 static friction coefficient

static friction coefficient is calculated by equation (2):

equation: μ S - static friction coefficient

fs - static friction, N

fp -- normal force, n

5.2 dynamic friction coefficient

dynamic friction coefficient is calculated by equation (3), where: μ D - dynamic friction coefficient

fd - dynamic friction, N

fp - normal force, n

5.3 friction coefficient instrument connection software, print the test report as follows

of which the net profit attributable to the shareholders of the parent company is 65.1 million yuan standard deviation δ S3. The machine cannot work without the voltage, and the dynamic standard deviation δ D represents the confidence of static and dynamic friction coefficient respectively,

us confidence = (1- δ s) × 10%

ud confidence = (1- δ d) × 100%

effectively judge the accuracy of the test data of this group, and it must be ensured that two tests at the same time with us and UD above are meaningful

in the composite flexible packaging industry, it is generally required that the dynamic and static friction coefficient of the inner bag is small and 0 The monthly export volume is maintained at about 800000 tons. For manufacturers of film packaging materials, the friction coefficient can be controlled by testing the opening agent, smoothing agent, type and content in the resin to meet the user's requirements

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