It has been shown that at semi crystalline polymers with devitrificated amorphous phase consideration as natural hybrid nanocomposites their anomalous high reinforcement degree is realized at the expense of crystallites partial recrystallization (mechanical disordering), that means crystalline phase participation in these polymers elastic properties formation. It is obvious, that the proposed mechanism is inapplicable for the description of polymer nano composites with inorganic nano fillers.