Cellulose nanocrystal–reinforced biodegradable polyesters: a comprehensive review of mechanical, thermal, and barrier property enhancements toward industrial implementation

The pursuit of environmentally sustainable and high-performance polymeric materials has driven intensive research into cellulose nanocrystals (CNCs) as nanoscale reinforcements for biodegradable polyesters. CNCs, isolated from biomass resources, offer exceptional mechanical strength, high crystallinity, and intrinsic biodegradability, making them ideal candidates for enhancing the thermal, mechanical, and barrier properties of widely used biodegradable polyesters such as poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), and poly(hydroxyalkanoates) (PHAs). While numerous reviews have covered CNC surface modification and processing, a critical gap remains in understanding how specific incorporation routes translate into property enhancements and industrial feasibility. This review uniquely bridges the gap by correlating processing strategies, interfacial chemistry, and structure–property relationships to the resultant improvements in crystallization, modulus, and gas- and moisture-barrier performance. Particular emphasis is placed on application-driven design and processing scalability, offering comparative insights across different bio-polyester systems. By integrating perspective from materials chemistry, polymer engineering, and industrial implementation, this work provides a comprehensive framework for advancing CNC-reinforced biodegradable polyesters toward large-scale, sustainable applications in packaging, biomedical, and structural materials.