Abstract: A staged feeding process for preparing a composition by mixing at least a first polymer and a second, dissimilar polymer forms a final composition comprising a uniform, small-particle dispersion of the first polymer in a matrix of the second polymer. Preferably, the first polymer has a melt viscosity greater than the second polymer. The process comprises the steps of feeding the first polymer in a first feed stage and feeding all of the second polymer as a melt at least two feed stages to mix the first and second polymers. Alternatively, the process may comprise feeding the first polymer in a first feed stage and feeding all of the second polymer in at least two feed stages subsequent to the first feed stage. In either case, this mixing initiates a chemical reaction between the first and second polymers.