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Effects of surface modification of halloysite nanotubes on the morphology and the thermal and rheological properties of polypropylene/halloysite composites

Abstract Effects of unmodified halloysite nanotubes (HNTs) and hexadecyl trimethyl ammonnium bromide treated halloysite nanotubes (CTAB-HNTs) on the morphology as well as the thermal and rheological properties of the HNT-filled polypropylene (PP) composites were investigated. The composites were melt-blended with a novel vane mixer dominated by extensional deformation. Fourier transform infrared spectroscopy well demonstrated that ammonium molecules were successfully interacted with halloysite groups. Compared with unmodified HNTs, the modified HNTs had a better dispersion in the PP matrix. The degree of crystallinity increased with the introduction of HNTs into the PP matrix. Thermal analyses revealed that CTAB-HNTs can improve the composites’ thermal stability compared with unmodified HNTs. As for dynamic shear rheology, the PP/CTAB-HNT composites showed higher viscoelaticity than neat PP in most frequency regimes, and that the raw HNT/PP composites presented the opposite phenomenon. The relaxation time of PP melt and the availability of heterogeneous PP domains increased with the presence of CTAB-HNTs.