(1) Test principle
The principle of the pendulum impact test is to make the hemispherical impact head impact and pass through the plastic film at a certain speed, and measure the energy consumed by the impact head as the evaluation of the pendulum impact energy of the plastic film. The test equipment used in the pendulum impact test is a pendulum film impact Tester, as shown in Figure 3-31.
Figure 3-31 Principle of pendulum film impact testing machine
1-sample support; 2,5-sample; 3-swing arm; 4-pendulum; 6-frame
For example, XBM-3 film impact testing machine is suitable for measuring the impact toughness of non-metallic materials such as plastics and rubber, and its main technical parameters are as follows.
①Maximum impact energy: 3J .
②Maximum swing radius: 320mm.
③Impact swing angle: 90°.
④ Sample jaw diameter: 89, 60, 50.
⑤ Punch size: 25.4, 12.7.
⑥Sample size: 100mm×100mm. ⑦ Dial graduation: 0.025J.
(2) Sample making and processing
Cut the sample evenly in the width direction of the film with acceptable appearance. The overall size of the sample is 100mm × 100mm or the diameter is 100mm. The number of samples in each group is 10. All samples should be conditioned for at least 4 hours in an environment with a temperature of (23±2)°C and a relative humidity of 45% to 55%, and the test should be carried out in this environment.
(3) Test method
The test is carried out according to the national standard GB 8809 "Pendulum impact resistance test method of plastic film". The specific test steps are as follows.
① Measure the thickness of the sample according to the national standard GB 6672, measure a point in the center of each sample, and take the arithmetic mean of the test results of 10 samples.
② Select the impact head so that the reading is within the range of 10% to 90% of the full scale.
③ Calibrate the instrument according to the requirements of the pendulum film impact testing machine.
④ Put the sample flatly into the holder and clamp it. There should be no wrinkles or excessive tension around the sample, and the impacted surfaces of the 10 samples should be consistent.
⑤ Turn the pointer to the maximum scale, quickly release the hook of the pendulum, make the pendulum impact the sample, and record the reading.
The test results are expressed as the arithmetic mean of 10 samples, accurate to 0.02J, and the standard deviation is reported. The calculation method of the standard deviation of the test results is:
In the formula, S - standard deviation;
Xi—measured value of a single sample;
x - the arithmetic mean of the test results;
n— the number of test values.
