Synergistic enhancement and spherulite growth mechanism of PLA composites by multi-dimensional mineralized cellulose nanocrystals.

Cellulose nanocrystals (CNCs) are promising reinforcements for bio-based polylactic acid (PLA); however, their one-dimensional (1D) structure limits their effectiveness due to insufficient hydrogen bonding with PLA chains and inadequate promotion of spherulite formation, resulting in suboptimal dispersion. To address this issue, this study introduces a novel approach by creating mineralized cellulose nanocrystals (MCNC) with multi-dimensional morphologies through in-situ CaCO growth. Three variants of MCNC are incorporated into PLA, including the MCNC variant, which features a 3D cubic crystal structure that significantly enhances PLA spherulite growth by providing additional nucleation sites. This leads to accelerated crystallization rates and an optimized crystal structure, as evidenced by a 3.9 °C reduction in cold crystallization temperature and a 17.1 % increase in crystallinity compared to pure PLA. Furthermore, the rigidity of inorganic CaCO₃ and the toughness of CNC synergistically enhance the mechanical properties of PLA composites through stress dispersion mechanisms, including a 34.6 % increase in tensile strength and an 84.3 % improvement in elongation at break, along with enhanced water permeability and faster degradation rates. Overall, this study presents a novel and multi-dimensional reinforcement strategy to effectively addresses the constraints of traditional CNCs, offering comprehensive improvements that make PLA/MCNC a viable eco-friendly substitute for agricultural mulch films and sustainable packaging solutions.