Hybrid fillers of lignin and carbon black for lowering of viscoelastic loss in rubber compounds

- In hybrid fillers, lignin molecules form coating layers on carbon black particles.
- Coating layer formation is promoted by π-π interactions between lignin and carbon black.
- Lignin in hybrid fillers assumes the shape and size of carbon black aggregates.
- Hybrid fillers are found responsible for reduction of filler networking of CB in rubber compounds.
- A reduction in filler networking leads to reduction of viscoelastic loss in rubber compounds.

This study investigates novel hybrid fillers for lowering of viscoelastic dissipation in rubber compounds by exploiting non-covalent interactions between lignin and carbon black (CB). Lignin is naturally occurring three-dimensional amorphous polymer consisting of phenyl propane units with hydroxyl, methoxy, and carbonyl substitutions and is capable of producing non-covalent interactions via π-π stacking with CB particles. The hybrid fillers are obtained by precipitating lignin from solutions onto carbon black particles. The fractal nature similar to CB particles and the presence of lignin coating layers on CB particles are confirmed by electron microscopy images. The coating layers are promoted by strong π-π interactions as revealed from Raman spectroscopy and 1H spin-lattice relaxation data and supported by a drop in zeta potential values. The hybrid fillers show much less networking than CB and reduce the viscoelastic dissipation in model rubber compounds by as much as 10% in comparison to the compounds of only CB.

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