An idea to deform highly crystalline polymer particles with unentangled macromolecules into nanofibers by shearing via viscous media has been exploited in the paper. It has been shown that nanofibers can be generated during uniform shearing of solid polytetrafluoroethylene, PTFE, particles dispersed in a molten polymer. PTFE powder particles should be of high crystallinity with unentangled macromolecules and should consist crystals with melting temperature exceeding that of equilibrium melting temperature (332-336 degrees C). The larger the deformation ratios and shear rates, and the longer the shearing times the thinner and stronger PTFE nanofibers are obtained. Shearing during compounding results in generation of PTFE nanofibers and thus, forming all-polymer nanocomposite. Isotactic polypropylene, high density polyethylene, low density polyethylene and atactic polystyrene were used as polymer matrices for the generation of all-polymer nanocomposites during compounding with selected PTFE powders. The process is characterized by simplicity just by shearing the dispersed crystalline polymer inclusions in another molten polymer. (c) 2013 Elsevier Ltd. All rights reserved.