Crystallization and morphological and crystal structures of PP in an in situ microfibrillar composite of modified PA66 with PP

An in situ-profiled microfibril-reinforced composite of modified polyamide 66 (mPA66) with polypropylene (PP) was prepared using a non-conventional compatibilization technique. The scanning electron microscope morphological observations showed in situ-generated, profiled microfibrils with a non-uniform diameter distribution and very rough surfaces with many pits and knots. The pits and knots were confirmed by the compatibilizer diffusion determined by the energy dispersive spectrum analysis. The presence of the PA66-profiled microfibrils shows the significant nucleation ability of the PP crystallization. Differential scanning calorimetry observations illustrated that the profiled microfibrils can accelerate the crystallization rate and increase the crystallization temperature. Obvious transcrystallization layers were observed through a polarized optical microscope. The β-crystalline phase of PP and larger, long period lamellar stacks were identified by small and wide-angle X-ray scattering measurements, respectively. These observations were very different from those of the simply blended samples of PP/PA66 in the presence or absence of the compatibilizer. Thus, the profiled microfibrils and improved interface adhesion may account for the powerful influence of PP on the crystallization and crystal structure.