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RUBBER HARDNESS

Elastomeric materials are usually measured with either a Shore A Scale Durometer or an IRHDdead load system. These tests are designed for use with samples approx 6mm thick, and a

surface area sufficient to permit at least 3 test points 5mm apart, 13mm from any edge.

Microhardness testers, Shore "A" Micro (M), or IRHD Micro (M), are utilised to measuresamples which are too small for testing with macro instruments.Shore

The Shore type instrument is a spring loaded indentation device, in which values are obtainedas a function of the viscoelastic property of the material. The truncated cone indentor, extends0.098inch (2.5mm)) and is pressed onto the sample against an 822g spring. Each 0.001 inch ofdeflection of the indentor is shown as 1 degree Shore (A), therefore, the harder the material, themore the deflection, the higher the number.

Materials reading below 10 degrees and above 90 degrees can be tested using Shore O & Dscales respectively. The scales "OO" is designed to read materials less than 10 Shore "O".Scales "B" & "C" are intermediate scales and the specifications are hybrids of the "A" & "D".

The microhardness tester reading Shore "A" Micro is basically a combination of "OO" Springand "D" Indentor (set at 0.050inch (1.25mm)). The instrument is comparative and is suppliedwith a set of reference blocks which enable calibration to the macro "A" value. IRHD

The IRHD (International Rubber Hardness Degrees) instrument has a spherical indentor whichindents the sample under a minor and major Load. The differential indentation depth ismeasured and tabulated to read directly in "IRHD" degrees. The displacement/IRHD degrees

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conversion table is published in ISO 48 : 1994. The standard shows three different combinationsof Ball & Loadings, (N) Normal, (H) High and (L) Low.Aplications

Material Instrument ExamplesSoft rubber,sponge rubber,skinned urethane foam,cork

Shore 0 & 00 Pad printers, fruit, tissues, automotive trim

Medium hard rubber,flexible polyurethane,soft polymers,felts

Shore A,Shore "A" Micro (M),IRHD,IRHD Micro (M)

General rubber parts, tyres, rollers, piano felts,sealants, seals, O-Rings

Medium hard rubber,polyurethane,plastics

Shore CAutomotive trim,hard rubber rollers

Hard rubber,rigid polyurethane,thermo plastics,epoxy resin

Shore D

Potting compounds,general plastic parts,vinyl flooring, brake pads,calendar rolls

Standards

BS 903-A26:1995, ISO 48:1994Physical testing of rubber. Method for determination of hardness(hardness between 10 IRHD and 100 IRHD)

BS 903-A57:1997, ISO 7619:1997Physical testing of rubber. Determination of indentation hardness bymeans of pocket hardness meters

BS EN ISO 868:1998 Plastics and ebonite. Determination of indentation hardness by meansof a a durometer (Shore hardness)

ASTM D1415-88(1999) Standard Test Method for Rubber Property-International Hardness

ASTM D2240-02 Standard Test Method for Rubber PropertyDurometer Hardness

DIN 53505Prfung von Kautschuk, Elastomeren und Kunststoffen; Hrteprfungnach Shore A und Shore D

DIN 53519-1Prfung von Elastomeren; Bestimmung der Kugeldruckhrte vonWeichgummi, Internationaler Gummihrtegrad (IRHD); Hrteprfungan Normproben

DIN 53519-2Prfung von Elastomeren; Bestimmung der Kugeldruckhrte vonWeichgummi, Internationaler Gummihrtegrad (IRHD); Hrteprfung

an Proben geringer