Kinetic stabilility of the well-exfoliated state in polypropylene-clay nanocomposites made by solid-state shear pulverization

Analysis by electron microscopy, x-ray diffraction/scattering and DSC has revealed that well-exfoliated states can be achieved in polypropylene (PP)-clay nanocomposites using a novel non-equilibrium processing method called solid-state shear pulverization (SSSP). Such well-exfoliated states cannot be achieved in PP/clay nanocomposites by melt processing. Nanocomposites made via SSSP have been found by x-ray and DSC analysis to remain well-exfoliated after 1.5 to 2 hr of annealing in the melt state of PP. Thus, even if a well-exfoliated state is not thermodynamically favored, it is kinetically stable over long times in the melt state.