ABSTRACT
The anthracite coal ground to 325 meshes, is ideally suited for low-cost hard rubber battery cases and covers having excellent dielectric properties. Also, the mold costs for the large battery cases in plastic are much higher than for standard hard rubber molds. Many of the hard rubber molds are used for low production items, and injection mold costs would not be economically feasible. The amount of sulfur used in a hard rubber battery container formula will vary from 12 to 30% on 100 parts of polymer. The amount of bound styrene in the polymer used and the compound viscosity will have significant bearing on the percentage of sulfur used. The vibration resistance of the hard rubber cases is much higher because of the heavier wall thicknesses. The batteries hold up longer in service than batteries with thin-walled thermoplastic cases.
