The hardness value of rubber increases with Carbon Black filler content. Initially it is between 50-70 Shore A. But with increase in Carbon Black content the value is going beyond 90. I am following the ASTM Standard D2240. According to this the for values more than 90 it has to be shifted to shore B. My concern is which hardness measurement needs to be followed Shore A or Shore B?
Mohammed Ibrahim Kittur: In general, you should shift to Shore B (by the way, would the Shore C or even D scale not be more adequate?), even if not performing a standardised investigation. If you are worrying about being unable to compare between the two scales, there are numerous comparisons between Shore hardness scales available (e.g. https://www.minerelastomer.com/technical-data/tecspak-features/shore-shore-d-comparison/ ) facilitating comparison. You might also want to measure your samples that show slightly less than 90 Shore A hardness with the Shore B setup and compile a plot with two Y axes (i.e. Shore A and Shore B hardness vs. carbon black content).
I would recommend Shore D which is typicall for (hard) rubber materials and should allow you to get reliable values from one method for all samples. If the soft materials could not be measured with shore D a combination of A and D would be suitable as Tomasz Jarosz pointed out.
The measurements of hardness of rubber by shore A, which scale graduated up to 100. on the other hand hard plastics measured by shore D, that also graduated up to 100. The difference between apparatus of hardness shore A and D related to
shape of pin of apparatus, which is cylindrical in Shore A, meanwhile pointed
The mechanical properties of rubber may not be good at high hardness. I think preference should be thermoplastic.
Dear Mohammed Ibrahim Kittur,
For measuring the hardness of rigid rubber such as Ebonite, Shore D is recommended. If the harness of rigid rubber is more than 58 Shore D, the Durometer (Shore A) would not show the accurate hardness which is more than 100.
You can verify the following link (Durometer hardness conversion table may be useful). Moreover, in the attached file, Table 1would be useful.
https://www.j-flex.com/how-is-rubber-hardness-measured-what-does-shore-hardness-mean/
Please see the maximum values of various shore hardness sales. At 100 all scales show the same readings. Shore A shows clumsy readings above 90 for harder materials. So it is better to shift to ther suitable scales lije shore B, C or D.
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