3.1 Ground coal is commonly used as an inexpensive filler in rubber compounds as a direct or partial replacement for carbon black or as a diluent in the compound.

3.2 Ground coal is very compatible with most rubbers and is very easily mixed into the compound.

1.1 This classification covers the compounding material known as ground coal. It is generally used in rubber compounds as a filler.

1.2 There are three grades of ground coal based on particle size, ash, and moisture. The selected values for these properties are suitable for use in a rubber compound.