Anisotropic nanoindentation of transcrystalline polypropylene by scanning force microscope using blade-like tips

A scanning force microscope was fitted with an elongated, blade-like tip, with which nanoindentations were performed in the transcrystalline isotactic polypropylene phase grown from the surface of high-modulus carbon fibers. The anisotropic Young’s modulus was evaluated by measuring the force–penetration curve of the indentation and the tip topography, as a function of the indentation depth. The modulus is 1.6–3 times higher when the longer axis of the indenting tip is perpendicular to the transcrystalline growth direction than when it is parallel to that direction. We discuss possible options for the lamellar arrangement in a transcrystalline isotactic polypropylene layer and, based on the present experimental data, propose a most likely model. © 1999 American Institute of Physics.