Fabrication of Hydrophobic Nanostarch With Moderate Radical‐Scavenging and Physical Barrier and Its Enhancement of the Aging Resistance of Natural Rubber

Anti‐aging agents are essential ingredients for high‐performance natural rubber (NR), extending its service life and broadening its applications. However, conventional anti‐aging agents suffer from several drawbacks, including volatilization, migration, and limited long‐term protection, which restrict their application in NR. Herein, we propose a scalable fabrication of nano‐starch with 81 nm mean diameter and molecular weight of 6.2 × 10 4 g/mol via enzymatic hydrolysis combined with high‐pressure homogenization. This sustainable and eco‐friendly anti‐aging agent exhibits moderate free‐radical scavenging activity and physical shielding effect, thereby enhancing the thermo‐oxidative aging resistance of NR. Subsequently, hydrophobic nano‐starch (Si7.5PMHNS) with 100 nm mean diameter was obtained through acid hydrolysis followed by efficient silane modification. The addition of 2.5 phr Si7.5PMHNS led to an elongation‐at‐break retention of 62.0% for NR/CB‐40/Si7.5PMHNS‐2.5 after 5 days at 100°C, corresponding to a relative increase of 24% compared with NR/CB‐40/6PPD‐1 (50.0%). Notably, enhanced interfacial compatibility and the absence of obvious voids were observed on the fracture surface of the rubber after thermo‐oxidative aging. This work presents a sustainable design strategy for starch‐based additives toward high‐performance, aging‐resistant NR composites, demonstrating that hydrophobic nano‐starch, as biomass‐derived anti‐aging agent, effectively elevates the aging resistance of NR while mitigating the environmental hazards associated with conventional anti‐aging agents.