Processing-driven alignment of carbon nanotubes and crystallization control in thermoplastic nanocomposites: In-situ structural and rheological analysis

This study investigates the coupled influence of shear-induced carbon nanotube (CNT) alignment and crystallization control in thermoplastic nanocomposites, providing real-time insight into processing–structure–property relationships. Using in-situ wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and rotational rheology, we track the evolution of CNT orientation and crystallization kinetics in a high-density polyethylene (HDPE) matrix under controlled shear. A critical shear threshold of ∼100 s −1 is identified, above which CNTs transition from a random to a highly aligned state, with the orientation factor increasing from 0.12 to 0.87. This alignment markedly accelerates crystallization, elevating the onset temperature by up to 8°C and reducing induction time by more than 50%. Aligned CNTs act as efficient nucleating agents and thermal pathways, generating anisotropic lamellar morphologies and enhanced thermal stability. The synergistic effects of CNT concentration and shear intensity yield a quantitative framework linking processing parameters, structural descriptors, and crystallization response. The methodology and correlations established here provide processing-embedded strategies to engineer thermoplastic nanocomposites with tunable thermal, mechanical, and structural performance, directly relevant to extrusion, fiber spinning, and additive manufacturing.