Natural rubber biocomposites reinforced with cellulose nanocrystals/lignin hybrid fillers

Abstract In this study, a novel hybrid system containing lignin and cellulose nanocrystals (CNC) is developed to reinforce natural rubber (NR) and produce high‐performance biocomposites. Firstly, the effect of lignin content in lignin/NR biocomposites is investigated. Despite lignin's advantages as an inexpensive biopolymer, its addition to NR results in longer cure time, reduced tensile strength and increased loss factor (tan δ); that is, lignin addition has a negligible reinforcing effect compared to conventional fillers, such as carbon black (CB). On the other hand, adding only 7.5 parts per hundred rubber (phr) of CNC to lignin/NR compounds decreased the curing time (14%) and loss factor (55% at 10% strain), while increasing the bound rubber content (37%), modulus at 100% strain (101%) and tensile strength (36%). CNC/lignin/NR bionanocomposites exhibited comparable mechanical properties and even better dynamical mechanical properties (53% lower loss factor at 10% strain) than conventional composites reinforced with CB. The optimum lignin content in the NR composite was 40 phr, while the percolation threshold for CNC was around 7 phr.