Mechanical Properties and Supramolecular Structure of Oriented Polyimide Films Filled with Carbon Nanofibers

The effect of carbon nanofibers introduced into the polyimide matrix on the mechanical properties of initial nanocomposite films and nanocomposite films oriented by uniaxial drawing at various stages of polyimide synthesis is studied. It is demonstrated that the storage moduli of nanocomposite films are higher compared to initial polyimide films at equal draw ratios. The self-orientation ability of the studied samples drawn at the stage of a prepolymer (poly(amic acid)) during thermal imidization is revealed, and it is shown that this ability increases upon the introduction of carbon nanofibers into the polyimide matrix. It is found that the polyimide films with the highest rigidity of macromolecules among the studied structures exhibit the highest storage moduli owing to their high self-orientation ability. Using X-ray diffraction and electron microscopy, a change in the supramolecular structure of rigid-chain polyimide films upon their orientational drawing at various stages of synthesis is investigated.