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

NBR, CR, CSM 44

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)