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Rubber hardness estimation


NR, low SBR, CIIR 40

Oil filled (25phr) SBR 31

High temperature SBR 37

Oil filled (37.5phr) SBR 26

IIR 35


Acrylonitrile content of more than 40% NBR 46

On the basis of the rubber compound, an increase of 1 per a filler or softener,following changes its hardness value:

FEF, HAF, EPC +0.5

ISAF +2.5

SAF, fumed silica +2.5

SRF +0.33

Aqueous silica based +0.4

Thermal black or hard clay +0.25

Calcium carbonate +0.167

Surface treated calcium carbonate +0.142

Mineral rubber -0.2

Lipid plasticizer -0.67

Aliphatic oil and naphthenic oil -0.5

Aromatic oil -0.588

To estimate the hardness = rubber hardness + packing (or softener dosage *Change of hardness value)