The present invention provides composite materials that contain formaldehyde-free aqueous binder compositions comprising defatted soy flour of no greater than 43 micron mesh particle size and polymer particles of at least one emulsion (co)polymer. Preferably, the defatted soy flour is present as an aqueous dispersion, or is in denatured form. Also provided are methods of making and using composite materials containing the formaldehyde-free binder compositions.