shore hardness
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Shore Hardness
Shore hardness is a measure of the resistance of
material to indentation by 3 spring-loaded indenter. The higher the number, the greater the resistance. The shore scleroscope measures hardness in terms
of the elasticity of the material. A diamond-tipped hammer in a graduated glass
tube is allowed to fall from a known height on the specimen to be tested, and the hardness number depends on the height to which the hammer rebounds; the harder the material, the higher the rebound
Introduction
Indenter
The Shore hardness is measured with an apparatus
known as a Durometer and consequently is also known as “Durometer hardness”.
The hardness value is determined by the penetration of the Durometer indenter foot into the sample.
Because of the resilience of rubbers and plastics, the hardness reading my change over time - so the indentation time is sometimes reported along with the hardness number.
The ASTM test number is ASTM D2240 while the analogous ISO test method is ISO 868.
Shore Test
The results obtained from this test are a useful
measure of relative resistance to indentation of various grades of polymers.
However, the Shore Durometer hardness test does not serve well as a predictor of other properties such as strength or resistance to scratches, abrasion, or wear, and should not be used alone for product design specifications.
Shore Test
Shore Scale is of two types:-
Shore A Shore D
The Shore A scale is used for “softer” rubbers while the Shore D scale is used for 'harder' ones.
Shore Scale
The shore A Hardness is the relative hardness
of elastic materials such as rubber or soft plastics can be determined with an instrument called a “Shore Durometer”.
If the indenter completely penetrates the sample, a reading of 0 is obtained, and if no penetration occurs, a reading of 100 results. The reading is dimensionless.
Shore A
The hardness testing of plastics is most
commonly measured by this test or Rockwell hardness test.
Both methods measure the resistance of the plastic toward indentation. Both scales provide an empirical hardness value that doesn't correlate to other properties or fundamental characteristics.
Shore Test Application
Shore Hardness is the preferred method for
rubbers/ elastomers. Shore Test is commonly carried out for
polymers such as:- Polyolefin Fluoropolymers Vinyls.
Shore Test Application
The Mohs scale of mineral hardness
characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material.
It was created in 1812 by the German geologist and mineralogist Friedrich Mohs
Mohs Scale
The Mohs scale of mineral hardness is based
on the ability of one natural sample of matter to scratch another.
The samples of matter used by Mohs are all minerals. Minerals are pure substances found in nature. Rocks are made up of one or more minerals.
As the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale.
Mohs Scale Arrangement
The hardness of a material is measured
against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material.
For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5.
Mohs Scale Arrangement
Mohs hardness Mineral Chemical formula Absolute hardness Image
1 Talc Mg3Si4O10(OH)2 1
2 Gypsum CaSO4·2H2O 3
3 Calcite CaCO3 9
4 Fluorite CaF2 21
5 Apatite Ca5(PO4)3(OH–,Cl–,F–) 48
Mohs hardness Mineral Chemical formula Absolute hardness Image
6Orthoclase Feldspar
KAlSi3O872
7 Quartz SiO2100
8 TopazAl2SiO4(OH–,F–)
2
200
9 Corundum Al2O3400
10 Diamond C 1600
The Mohs scale is a purely ordinal scale. For
example, corundum (9) is twice as hard as topaz (8), but diamond (10) is almost four times as hard as corundum.
Mohs scale Non-uniformity
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