Effect of tetra-needle-shaped zinc oxide whisker (T-ZnOw) on mechanical properties and crystallization behavior of isotactic polypropylene

Isotactic polypropylene (iPP) composites with unmodified and modified tetra-needle-shaped zinc oxide whisker (T-ZnOw) were prepared via melt blending in a twin-screw extruder. The mechanical properties, thermal properties, morphology and crystallization behavior were investigated. The mechanical properties of iPP with T-ZnOw modified by silane based coupling agent were much better than that of iPP with unmodified T-ZnOw. The reason was that the interfacial interaction between T-ZnOw and iPP matrix became stronger when T-ZnOw was modified by coupling agent. Besides, the addition of T-ZnOw improved thermal properties of iPP, including heat deflection temperature and thermal degradation temperature. Furthermore, wide angle X-ray diffraction (WAXD) results showed that T-ZnOw can be used as a novel β-nucleating agent, and the relative content of β-crystal was 0.38 when T-ZnOw content was 5 wt.%. iPP/T-ZnOw composites were found to exhibit higher crystallization temperature, smaller spherulites, and faster crystallization rate than those of pure iPP, indicating that T-ZnOw played a role of nucleating agent on the crystallization of iPP and could induce accelerated crystallization.