Transcrystalline Polypropylene-Based Honeycomb Structures Spontaneously Induced on Amphiphilic Cellulose Nanofibrils Prepared by Aqueous Counter Collisio

Cellulose nanofibrils prepared by aqueous counter collision method (= ACC-CNFs) favorably cover the surface of isotactic polypropylene (iPP) microspheres simply by mixing in the ACC-CNFs aqueous dispersion. Recently, the authors proposed that an impact-resistant composite material was successfully obtained from the iPP coated with ACC-CNFs via usual injection-molding process. This improved impact-tolerance appeared due to embedding of a three-dimensional framework of CNFs resembling a plant cell wall structure (=“plant cell wall”-mimicked frameworks) of ACC-CNFs that contribute to synergetic effects for the improvement in the mechanical properties. In this study, it is focused to elucidate crystallization of iPP on the ACC-CNFs scaffolds. Thermal analyses indicated that ACC-CNFs was likely to induce transcrystallization of α-form of iPP. Moreover, the crystallization was strongly influenced by ACC-CNFs with different cellulose sources. Microscopic observations demonstrated that the transcrystalline structure, which was similar to shish-kebab formation, involved honeycomb-like frameworks of ACC-CNFs. In addition, its crystalline growth of iPP was possibly conducted by accumulation of a two-dimensional crystalline disk.