Nonlinear viscoelastic behaviour of self-healing natural rubber/carbon black nanocomposites with ionic crosslinks

Elastomeric composites are widely used in dynamic mechanical applications owing to their excellent elasticity, resilience, and durability, while their nonlinear behavior under dynamic loading conditions is often unpredictable, due to the complexity of the network’s structures. Introducing reversible bonds to the polymer networks could be useful in dissipating local energy concentration and homogenising the polymer networks, so that reducing the nonlinearity and stabilising the dynamic mechanical responses. In this study, dynamic ionic bonds were introduced to natural rubber (NR)/carbon black (CB) nanocomposites by incorporating propenyl zinc methacrylate (pZnMA) complexes. The dynamic mechanical properties, nonlinearity analysis, and self-healing behavior were evaluated through Fourier-transform oscillatory rheology within strain amplitude (0.1 ∼ 500%) and stress decomposition (SD) analyses. The self-healing properties were evaluated by both mechanical testing and rheology analysis. The microstructural characteristics of the self-healable samples were evaluated using small- and wide-angle X-ray scattering (SAXS/WAXS). The pZnMA incorporated NR vulcanizates exhibited comparable mechanical properties to the control sample but had up to 89% self-healing efficiency. Nonlinear rheology demonstrated its lower energy dissipation and more stable viscoelastic responses. The 3 rd -order Chebyshev coefficients calculated from SD analysis highlighted strain stiffening with an earlier transition to shear thickening behaviour, as compared to the control sample, indicating the reconfigurable and adaptive nature of the dynamic ionic networks. The pZnMA ionic crosslink network provides a dynamic and recoverable intermediate structure with improved interfacial homogeneity and resistance to transient deformation. This research provides valuable insights into designing next-generation durable, self-healing elastomeric composites with enhanced mechanical performance and resilience. • Dynamic ionic crosslinks via pZnMA complexes enable self-healing of NR/CB nanocomposites. • Up to 89% recovery in tensile strength and elongation was achieved, while maintaining comparable mechanical properties to conventional sulfur-cured systems. • Lorentz-corrected SAXS/WAXS revealed suppressed microphase separation and enhanced interfacial homogeneity in the ionic-crosslinked networks. • Fourier-transform rheology (FT-LAOS) and stress decomposition (SD) analyses demonstrated reduced Payne effect, stable nonlinear viscoelasticity, and an early onset of strain stiffening in pZnMA systems.