Plasticizer-Dependent Vulcanization, Crosslinking, and Magneto-Viscoelasticity of Natural Rubber-Based Magnetorheological Elastomers

Adaptive vibration control under variable dynamic loading requires damping materials that combine structural stability, efficient energy dissipation, and field-tunable mechanical response. Here, natural-rubber-based magnetorheological elastomers containing coumarone resin (MRE-C), naphthenic oil (MRE-N), or paraffin (MRE-P) were systematically compared through microstructural characterization, dynamic viscoelastic testing, vulcanization kinetics, and equilibrium swelling. MRE-C exhibited pronounced strain-induced softening, whereas MRE-P showed a high relative dynamic sensitivity but limited absolute stiffness. MRE-N achieved the most favorable overall balance, with more continuous anisotropic particle-chain structures and the lowest Payne-effect amplitude (37.90%). At 5 A, its storage modulus increased by 25.8%, close to the 30.9% increase in MRE-P, while maintaining substantially higher absolute G′ and G″ and a nearly unchanged tan δ. MRE-N’s macroscopic advantage was associated with more favorable network formation, with 17.9% and 7.4% lower apparent activation energies and 7.2% and 18.1% higher apparent crosslink densities than MRE-C and MRE-P, respectively. Molecular simulations of representative sulfur bridges further indicated that monosulfidic bridges favored geometric constraint and structural recovery, whereas disulfidic bridges exhibited greater conformational adaptability. These results link plasticizer-dependent vulcanization and crosslinking state with macroscopic magneto-viscoelastic performance and identify naphthenic oil as the most effective of the investigated plasticizers for balancing stiffness, energy dissipation, and magnetic responsiveness.