Unveiling the Impact of Cellulose Nanofiber on the Mechanical Properties and Strain‐Induced Crystallization Mechanism of <scp>ENR</scp> Nanocomposites

ABSTRACT Understanding strain‐induced crystallization (SIC) is essential for developing high‐performance elastomers. In this study, epoxidized natural rubber (ENR) nanocomposites with 1–5 phr unmodified cellulose nanofibers (CNFs) were prepared via latex mixing and peroxide crosslinking. The objective was to investigate the influence of CNF loading on the SIC and reinforcement of ENR. The results revealed that nanofibers remained well‐dispersed at the nanoscale throughout the ENR, regardless of the loading amount. This allowed effective interfacial interaction between the CNFs and ENR, which accelerated the SIC during stretching. The strengthening mechanisms of the CNF/ENR nanocomposites were clearly different between low (1–2 phr) and high (3–5 phr) CNF amounts. At low CNF amounts, the CNF‐ENR interaction was mainly hydrogen bonding, moderately improving SIC and mechanical properties. At higher amounts, both hydrogen bonding and the additional mutual entanglement between CNFs and ENR contributed to significant improvements in SIC and mechanical properties. The strength of ENR with 3 and 5 phr CNF increased by about 40% and 75%, respectively. Our results demonstrate that using interfacial interactions and nanofiber orientation is an effective way to create strong, flexible, and eco‐friendly elastomers with minimal filler. These findings provide insight into the structure–property relationships for next‐generation rubber materials.