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IRHD Rubber Hardness Tester
Hardness is one of the most important properties which determine the suitability of any rubber component for its intended end use. Incorrect hardness may defeat the basic purpose for which the component is designed. Thus accurate and reliable determination of hardness is of extreme importance in rubber field.
Amongst the various means for the determination of rubber hardness the most important ones are the Durometer and the IRHD Hardness Tester. While the first uses the principle of indentation of a truncated cone in rubber under varying loads acting through a spring, the second method uses a fixed dead load acting on a hemispherical indenting tip. Whereas the first method suffers from the disadvantage of permanent set getting developed in the spring and thus affecting its accuracy, the second method, being based on dead load principle, is free from this problem.
The PROLIFIC IRHD Hardness Tester is a table model equipment suitable for reference testing of hardness of rubber or similar polymers in the laboratory. It consists of a plunger rod carrying a hardened hemispherical tip of the specified diameter at its lower end. The rod is located within a cylindrical guide and is constrained to move inside it. The base of the guide acts as the pressure foot surrounding the point of indentation. Under normal condition the pressure foot extends below the indenting tip, thus preventing it from getting damaged. An indenting load is positioned over the plunger rod without directly acting on it.
The test specimen having flat and parallel top and bottom faces is placed on a horizontal platform located below the indenting tip. The platform can be raised up by rotating a screwed wheel. This upward movement of the platform causes the test specimen to come in contact first with the pressure foot and later with the indenting tip under the specified contact load.
Depth of penetration of the indenting tip into the test specimen is determined with the help of a dial indicator fitted at the top of the pressure foot assembly. The contact between the dial indicator and the top of the plunger rod is made through an electrical arrangement to ensure that the weight of the stem of the dial indicator does not act on the test specimen. An electric buzzer is provided to give low intensity vibrations to the plunger rod to eliminate friction. The dial indicator gives the depth of indentation in units of 0.01 mm, which can be converted into IRHD hardness values with the help of a standard table provided with the equipment.
The tester is finished in grey hammertone stoving painting and bright chrome plating to give it a corrosion resistant finish. Three models of the tester are available to cover different ranges of hardness.
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TECHNICAL DATA
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STANDARD MODEL
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LOW STANDARD MODEL
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HIGH STANDARD MODEL
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Range of hardness
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30 to 85 IRHD
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10 to 35 IRHD
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10 to 35 IRHD
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Diameter of indentor tip
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2.50 mm
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5.00 mm
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1.00 mm
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Pressure foot
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20 mm OD
6 mm ID
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22 mm OD
10 mm ID
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20 mm OD
6 mm ID
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Force on pressure foot
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8.30 N
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8.30 N
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8.30 N
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Contact force
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0.30 N
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0.30 N
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0.30 N
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Indenting force
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5.40 N
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5.40 N
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5.40 N
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Electric supply
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230 volt single-phase AC
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RELATED STANDARDS
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IS 3400 (Part 2) - 1980
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Methods of Test for Vulcanized Rubber
Part 2 - Hardness
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ISO 48 - 1979
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Vulcanized Rubbers (30 to 85 IRHD)
Determination of Hardness
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ISO 1400 - 1975
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Vulcanized Rubbers of High Hardness (85 to 100 IRHD)
Determination of Hardness
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ISO 1818 - 1975
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Vulcanized Rubbers of Low Hardness (10 to 35 IRHD)
Determination of Hardness
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