he hardness of plastic products refers to the ability of the surface of the product to resist mechanical pressure. The size of this ability is related to the tensile strength and elastic modulus of the measured plastic. Commonly used detection method, according to the different shape of the test head can be divided into Shore hardness, Brinell hardness and Rockwell hardness.
(1) Shore hardness test test method Shore hardness test using Shore hardness tester, the instrument uses the standard spring pressure, pressure head for the conical, indenter plane φ0.8mm.
The test sequence is as follows.
① according to the instructions, with the hardness of standard parts debugging pressure, together with the standard value.
② the imprint head on the smooth plate or glass plate, verify the hardness value of 100.
③ the sample flat on the smooth metal plate, for the pressure head to exert (1 ± 0.01) kg load, pressure 30s, then the record value is Shore hardness value.
⑵ Brinell hardness test method Brinell hardness test with a standard diameter (φ2.5mm, φ5mm or φ10mm) surface smooth and have a certain hardness of the round ball for the indenter. When the pressure is measured, the indenter is pressed on the specimen, and the load is applied to the indenter evenly (the load is shown in Table 1), the pressure time is 1min, the indentation depth after the steel ball pressure specimen is measured after unloading, You can calculate the Brinell hardness (MPa) of the sample.
Testing of hardness of plastic products
Where HB - Brinell hardness, MPa;
P - pressure load, N;
D - ball diameter, mm;
h - the depth of the indentation after the ball is pressed, mm.
Table 1 sample load size
Hardness range (HB) Sample thickness / mm Ball diameter / mm Load / kg
> 36> 6 5 250
20 ~ 36> 6 5 125
8 ~ 20 6 ~ 10 5 62.5
⑶ test test precautions
① before the test sample in the standard temperature environment, the storage time of not less than 16h.
② test test indenter 1min time after unloading indentation depth measured.
③ detection test when the number of indentation center distance of not less than 25mm.
④ The load accuracy of the pressure head is ± 1%.
⑤ detection of indentation depth of the instrument accuracy of 0.01mm.
⑥ sample thickness uniform, smooth surface.
⑦ Shore hardness test specimen thickness should be not less than 6mm.
⑧ a number of sample indentation, calculated after taking the average hardness of the sample.
⑷ Rockwell hardness test Rockwell hardness test used in metal heat treatment after the hardness of the metal surface hardness of the higher detection. Test with the standard pressure head (ball or cone angle 120 ° diamond cone), the first test force, and then add the main test force, and then return to the initial test force. The surface hardness HR of the specimen was calculated by the difference of the depth difference between the pressing head and the specimen under the two test forces.
Testing of hardness of plastic products
Where HR - Rockwell hardness value;
e - After unloading the main test force, the indentation is deep under the initial test force, mm;
c - calculate the constant, take 0.002mm.
With different pressure head and the main test force with, available HRA, HRB and HRC Rockwell hardness scale.