AbstractSince silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound wil have poor dispersion of the filler and a poor cure characteristic. Improvement of properties of silica‐filled styrene‐butadiene rubber (SBR) compounds has been studied using emulsion SBR‐based acrylonitrile‐styrene‐butadiene rubber (NSBR). The silica dispersion is improved by adding NSBR to the compound. The bound rubber content increases with increase in the NSBR content. The scorch time and cure rate become faster as the NSBR content increases. The crosslink density also increases by increasing the NSBR content. The wear property is improved by adding the NSBR. Copyright © 2003 John Wiley & Sons, Ltd.