Phase transformation and mechanical properties of halloysite nanotubes‐modified isotactic polypropylene filaments

Abstract

ABSTRACT Phase transformation and mechanical properties of isotactic polypropylene (iPP) with well‐distributed 0.3, 0.8, and 1.2 wt % halloysite nanotubes (HNTs) are studied. The spatial distribution of HNTs in the iPP matrix is analyzed using transmission electron microscopy and found to be homogeneously dispersed. Phase transformation from molten to solid states is characterized by polarized optical microscopy under an isothermal condition at different temperatures and differential scanning calorimetric in cooling and heating at different rates. Average size of spherulites, the degree of undercooling and total solidification time of iPP decrease as the amount of HNTs increases, suggesting HNTs act as nucleation sites for iPP. More interestingly, the wide‐angle X‐ray diffraction analysis only showed the formation of the α‐form iPP crystallites for the extruded filament, while kinetics results indicating the existence of β‐form crystals. These results together demonstrated the presence of HNTs leads to heterogeneous phase distribution which enhances the mechanical strength of the iPP filaments without reducing their ability for elongation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44714.