Hybrid filler and coupling agent: Effect of partial replacement of carbon black with talc and silane on properties of natural rubber compound

This study investigates a sustainable hybrid-filler strategy for natural rubber (NR) compound by partially replacing petroleum-based carbon black (CB) with talc and introducing a silane coupling agent to mitigate interfacial incompatibility. Compounds containing CB, CB+talc and CB+talc+increasing silane were produced via two-stage mixing and characterized for morphology (dispersion/mapping), curing and flow behavior (differential scanning calorimetry DSC/moving die rheometer, MDR/Mooney), crosslink density (Flory–Rehner), physical–mechanical properties, dynamic performance (Payne effect/heat build-up/tension–fatigue), and thermal stability (aging/thermogravimetric analysis,TGA). Talc reduced the compound viscosity, offering processing benefits. The swelling test indicated that talc decreased crosslink density, but silane recovered it, forming covalent linkages. Tensile strength and elongation at break were improved without altering hardness. Dynamically, talc increased heat build-up, whereas silane inverted the trend and reduced the temperature rise gradually from 41.5 to 29.4 °C at 2 phr. Fatigue life was improved with talc (~10%), and further with silane (up to 36% at 2 phr), highlighting a favorable stiffness– fatigue balance with compatibilization. Overall, partial CB replacement by talc, in combination with silane, delivers meaningful sustainability gains with improved dynamic performance while preserving key mechanical properties of NR compounds.