A coarse-grained molecular dynamics study on the mechanical behavior of carbon black reinforced natural rubber composites

TZ Zhang and HY Guo and Q Li and FL Zeng, COMPUTATIONAL MATERIALS SCIENCE, 259, 114167 (2025).

DOI: 10.1016/j.commatsci.2025.114167

This study employs coarse-grained molecular dynamics (CGMD) to investigate mechanical reinforcement in carbon black (CB) filled natural rubber (NR) nanocomposites. Force fields were developed using the effective force coarse-graining (CB-CB) and iterative Boltzmann inversion (CB-NR/NR-NR) methods. Uniaxial tensile simulations revealed that introducing CB nanoparticles (NPs) significantly enhances the Young's modulus and tensile strength. Optimal reinforcement occurs at 20 & Aring; (medium size) at a filler loading of 40 phr (parts by weight per hundred parts of rubber), due to the synergistic mechanisms: improved CB dispersion, enhanced NP-NP energy dissipation, NP-induced NR chain alignment/crystallization, and NP-NR interface formation. On the other hand, smaller NPs increase stress distribution heterogeneity attributed to higher particle density, as evidenced by reduced von Mises stress. Furthermore, polymer-grafting onto CB NPs improves mechanical properties, with the net effect determined by grafting density (E). While the dispersion of CB NPs and bridging networks among CB, grafted chains, and the NR matrix improve with increasing E, the wrapping behavior of grafted chains around CB NPs emerges as the dominant mechanism inhibiting further mechanical improvement at higher E. Interfacial analysis (energy dissipation, volume fraction of micro-void, stress distribution) confirmed that grafting polymer enhances interfacial load transfer but excessive E induces chain wrapping that limits mechanical enhancement. In a word, the work deciphers the microstructure-performance relationships governing nanocomposite design, unraveling the intrinsic mechanism of nanoparticle size-dependent macroscopic mechanical properties, and demonstrating the dual role of interfacial architecture in reinforcement.

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