Styrene-butadiene latexes were prepared in the absence of an emulsifier using a redox initiator Fe(NO3)(3)/H2O2. Their positive charge was supplied by comonomer N,N-diethyl aminoethyl methacrylate. At a given styrene-butadiene ratio (60/40) the particle size depends on the concentration of the comonomer and initiator. The latexes are stabilized by electrostatic repulsion, and remain positively charged and stable up to pH 8. At a higher pH, they acquire a negative charge and restabilize. The positively charged particles deposit readily on negatively charged fibers dispersed in water, thus covering the fiber surface. Upon dewatering and drying, the particles coalesce, and the fibers become covered by a polymeric film, which improves the interfiber bonding and, consequently, the mechanical properties of the fiber assembly. (C) 2000 John Wiley & Sons, Inc.