Nanoscale shear and indentation measurements in transcrystalline alpha-isotactic polypropylene

The relation between the mechanical, properties and the lamellar morphology of the a-isotactic polypropylene transcrystalline interphase in a fiber co mposite was investigated by means of nanometric sheer and directional inden tation measurements, using scanning force microscopy. Measurements were per formed along directions parallel and perpendicular to the transcrystalline growth direction. a key finding is the inversion of the shear modulus aniso tropy ratio from 2.3 to 0.5 as the crystal grows away from the fiber. On th e basis of this finding, an improved view of the hierarchical lamellar and molecular order of the transcrystalline layer is proposed.