By utilizing the process of this invention, the adhesion between polymeric reinforcements and rubber compositions can be greatly improved. This invention more specifically discloses a process for preparing a rubber article containing a polymeric reinforcement which comprises: (1) plasma treating the polymeric reinforcement in a manner whereby reactive groups containing Zerewitinoff active hydrogen atoms are bonded to the surface thereof; (2) incorporating the polymeric reinforcement having Zerewitinoff active hydrogen atoms bonded to the surface thereof into an uncured rubber composition, wherein said rubber composition has pendant blocked isocyanate groups bound thereto; and (3) curing the uncured rubber into the desired shape for the rubber article at an elevated temperature sufficient to deblock the isocyanate groups bonded to the uncured rubber allowing for the isocyanate groups to react with the Zerewitinoff active hydrogen atoms bonded to the surface of the polymeric reinforcement.