Controlling Drying to Regulate Green Strength for Enhanced Mechanical Properties of NR/GO/CB Composites

Natural rubber (NR) exhibits excellent mechanical properties and processability, but its molecular structure is highly sensitive to thermo-oxidative environments. Particularly during the drying stage, radical-induced oxidation could promote thermo-oxidative degradation, leading to a significant decline in both green strength and the mechanical properties of vulcanized rubber. To address this issue, the effects of drying temperature (40°C–80°C) on the microstructure and green strength of natural rubber/graphene oxide (NR/GO) raw rubber were systematically investigated through experiments and molecular dynamics (MD) simulations. Subsequently, the mechanical properties of the corresponding natural rubber/graphene oxide/carbon black (NR/GO/CB) vulcanizates were evaluated to elucidate the relationship among the drying process, raw rubber structure, and vulcanization performance. The results indicated that lower drying temperatures (40°C) produced higher green strength in raw rubber (4.8 MPa). By better preserving structural stability and the effective chain-entanglement network, low-temperature drying favored strain-induced crystallization and more effective stress transfer during stretching, enhancing the tensile strength of the NR/GO/CB composites by approximately 8%. Furthermore, the better-preserved molecular and interfacial structure facilitated the formation of a more stable filler–rubber network, reducing heat build-up by approximately 40%. These combined effects collectively improved the mechanical properties of the NR/GO/CB composites. MD simulations further indicated that elevated temperatures increased oxygen mobility and NR-chain mobility, providing molecular-level trends consistent with the experimentally observed intensification of thermo-oxidative degradation. This study established a processing-structure–property framework and provided a feasible drying strategy for the industrial production of high-green-strength NR/GO/CB composites with improved mechanical performance. Highlights Elucidate the structural changes of raw rubber during the drying process. Establish the structure–property relationship of raw and vulcanized rubber. Regulate the green strength of NR/GO through the drying process.