Dependence of microstructures and melt behaviour of polypropylene/fullerene C60 nanocomposites on in situ interfacial reaction

Polypropylene (PP)/fullerene C-60 nanocomposites, in which the interfacial reaction between two components was in situ mediated by peroxide, were prepared by a melt mixing method. Structural characterization showed that the interfacial reaction strongly affected the microstructures of PP/C-60 nanocomposites at different scales, such as improving the dispersion state of C-60 nanoparticles and forming long chain branched structures in which C-60 acts as a branching point. This was ascribed to the ability of C-60 (as a reactive nanoparticle) for preferentially trapping carbon-centred macroradicals of PP to in situ form long chain branched structures of PP on the surface of C-60 during melt mixing. As a result, the shear-responsive sensitivity of the nanocomposite melts in low shear frequency regions was dramatically enhanced compared to parent PP and the nanocomposites without interfacial reaction. The nanocomposites also showed high melt strength. In addition, the transition from the melt state to solid state (crystallization process) occurred at higher temperature after the interfacial reaction between PP and C-60 took place.