Excellent toughness, crystal morphology and crystallization mechanism of transcrystallization of polypropylene induced by layered interface

The performances of isotactic polypropylene (iPP) have always been related to its crystal morphology and structure. In this work, β ‐transcrystallization ( β ‐TC) was obtained by constructing iPP and β ‐nucleated iPP ( β ‐iPP) multilayered structures. By changing the number of layers, the β ‐TC content in layered samples was controlled. During the isothermal crystallization at 130°C, the β ‐nucleating agents induced β ‐spherulites in β ‐iPP layers, then the β ‐nucleus at the interface induced the formation of β ‐TC which grew vertical to the interface in iPP layers. Compared with traditional blending sample which had only β ‐spherulites, the crystallization rate, and Avrami exponent of β ‐crystal in layered samples decreased with increasing of the β ‐TC content due to the longer induction nucleation time and two‐dimensional heterogeneous growth mode of β ‐TC during isothermal crystallization at 130°C. Similarly, the crystallization rate of β ‐crystals decreased with the increase of β ‐TC content during nonisothermal crystallization. In addition, the layered sample with high content of β ‐TC showed good toughness, due to the special morphology of β ‐TC. This study provided a method to fabricate β ‐TC during melt processing, and promoting the application of iPP materials with high‐content of β ‐TC. POLYM. ENG. SCI., 58:1791–1799, 2018. © 2017 Society of Plastics Engineers