NR 40-45 ShA rubber formulation

Can someone provide the formulation of a NR compound, with hardness= 40-45 ShA and 14 MPa Tensile strength? I need the compound with a high viscosity. Other compounds of this type, with low viscosity, originate a lot of dirt in our molds. And, I need a fast acceleration.


The formulation that follows should meet ASTM D2000 callout M4AA414 A13 B14. Quantities are given in phr.

  • SMR10 100.00
  • N330 1.00 (yes, just 1.00phr)
  • Whiting 50.00
  • Process oil 10.00
  • Zinc oxide 3.50
  • Stearic acid 1.00
  • Flectol H (TMQ) 1.00
  • Sulphur 1.50
  • MBTS 1.50
  • TMTD 0.15

Mooney viscosity = 60.
Curing test specimens at 150°C for 20mins should give you the following properties:
Tensile = 17.5MPa, EB = 660%, Shore A = 42°, Compression set (1 day at 70°C) = 11%.

Could the “dirt” be nothing more than mould fouling? This will always occur with ZnO/sulphur systems. The literature shows that most fouling is caused by a build up of zinc sulphide.

Above is a snippet.