Interfacial Crystallization of Poly(L‐Lactic Acid) Induced by Carbon Nanotubes in Single Fiber Composites

The incorporation of nanofillers into biodegradable polymers is an effective approach to improve the physical properties and mechanical performance for various practical applications. In particular, the interfacial microstructure between the polymer and nanofillers plays a critical role in determining the macroscopic properties of the resulting polymer nanocomposite. In this work, we report carbon nanotube (CNT) induced interfacial transcrystallization of poly(L‐lactic acid) (PLLA) in the single‐fiber composite. The dynamic process of PLLA transcrystallization around the single CNT fiber is investigated under isothermal crystallization in the temperature range from 124°C to 136°C using in situ polarized optical microscopy. Transcrystallization kinetics are analyzed based on polymer heterogeneous nucleation and crystallization theories. The interfacial free energy difference parameter (Δσ/σ = 0.057) and the fold surface free energy (σ e = 5.82 × 10 −2 J/m 2 ) are calculated to assess the nucleation ability and crystallization barrier, respectively. Atomic force microscope (AFM) analysis reveals radially aligned edge‐on lamellar crystals adjacent to the CNT fiber. Alternative transformation from the edge‐on lamellar orientation to a flat‐on orientation results in a banded transcrystalline texture. A proposed mechanism is presented that lamellar twisting during the crystal growth is attributed to the banded transcrystals.