A binder is applied to fibers to bind particles to the fibers. The fibers have hydrogen bonding functional groups. The particles have functional groups capable of forming a hydrogen bond or a coordinate covalent bond. The binder comprises binder molecules, the binder molecules having at least one functional group that is capable of forming a hydrogen bond or a coordinate covalent bond with the particles, and at least one functional group that is capable of forming a hydrogen bond with the fibers. A substantial portion of the particles that are adhered to the fibers are adhered in particulate form by hydrogen bonds or coordinate covalent bonds to the binder, and the binder is in turn adhered to the fibers by hydrogen bonds. Fibers containing particles bound by this method are easily densified.