This study looks at the effects of imposed confinement on morphology related properties in vapor grown carbon nanofibers (VGCF)-polypropylene nanocomposite melt-mixed extruded filaments. Different levels of imposed confinement are achieved through varying the content of the VGCF and the dimensions of the nanocomposite filaments. The resulting molecular confinement is apparent through a sharp increase (termed the inversion point) in a number of properties at low filament diameters, which is associated with a formation of a 'shish-kebab' structure and a transition from a skin/core morphology to an axially oriented lamellar structure. This formation of a highly orientated lateral lamellar structure as the monofilaments’ diameter is decreased, which is responsible for an abrupt jump in the mechanical properties, is facilitated markedly by the nanofibers. The experimental results show that two factors - either or both – might potentially be active, namely, the effects of the nanofibers on nucleation and orientated crystallization and on confinement at inter-overlapping nanofiber regions. The argument for confinement is that it appears to generate a sharp property change as a function of diameter, possibly indicating that a specific molecular dimension is attained, e.g., the radios of gyration of the polymer chain.
