Characterization of solution-mixed polypropylene/clay nanocomposites without compatibilizers

A solution mixing technique along with three organically modified montmorillonites (O-MMTs, denoted 15A, 20A and 30B), respectively, were used to prepare polypropylene (PP)-based composites. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the O-MMTs were intercalated and/or partially exfoliated within the PP matrix to different extents. The PP/O-MMT nanocomposites were thus achieved without employing any compatibilizer. The 15A was noted to exhibit the best nano-scaled dispersion status among the O-MMTs used, which was attributed to its more organophilic characteristic. Differential scanning calorimetry (DSC) results indicated the O-MMTs improved the crystallization ability of PP slightly in the composites, whereas the melting temperature of PP hardly changed. Thermogravimetric analysis (TGA) confirmed the thermal stability enhancement of PP after adding the O-MMTs; the enhancement followed the order of PP/20A system > PP/15A system > PP/30B system. XRD results also revealed the existence of predominant α form PP crystals along with a minor amount of γ form crystals in the composites.