Revealing the structures and dynamics of isotactic polypropylene bound to carbon fibers

The addition of fillers affects the overall rheological and mechanical properties of polymers mainly due to the creation of the nanometer-size bound polymer layer (BPL) at the filler surface, at which the polymer has a different behavior than in the bulk. In spite of their importance, the development and optimization of the BPL interface is still based on empirical know-how strategies since the actual mechanism of reinforcement at the polymer/filler interface remain unresolved. Here we present the structures and dynamics of the BPL layer formed on carbon fiber (CF) surfaces. CF/isotactic polypropylene (iPP) nanocomposites play an integral role in a number of industrial applications. Based on a solvent-rinsing method, we successfully prepared the BPL on the CF from CF/iPP composites and characterized the in-situ structures and local segment dynamics of the BPL alone using small-angle neutron scattering and neutron backscattering, respectively. In addition, we mimicked the interface using iPP thin films deposited on carbon layer coated planar silicon substrates and the melting behavior of the BPL alone (after the solvent rinsing process) were investigated by using in-situ atomic force microscopy and grazing-incidence X-ray diffraction.