Study on mechanical and electrical properties of cellulose nanofibrils/graphene-modified natural rubber

Abstract

Abstract To improve the mechanical and electrical properties of natural rubber (NR), we used cellulose nanofibrils (CNF) as biotemplates, dispersing conductive graphene composites at 10% and 7.5% and coated graphenes (GNS) between natural rubber molecules on the CNF surface by solution blending. The conductive CNF-GNS/NR nanocomposite material was prepared by dispersing and overlapping CNF and GNS in NR to form a three-dimensional multi-layered network structure composite. The product was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile testing, and conductivity testing. Results show that the combination of GNS and CNF did not clearly change the GNS chain, did not destroy the GNS structure, and maintained GNS conductivity. When 10% GNS was added, the draw ratio of the CNF-GNS/NR composite was 208%, 56% higher than that of pure NR. The tensile strength increased by 340% compared with pure NR and was 79% higher than that of CNS without CNF. The percolation threshold of CNF-GNS/NR was between 5 and 7.5 phr, lower than the 7.5–10 phr permeation threshold of GNS-NR. When 7.5% GNS was added, the conductivity of CNF-GNS/NR was 3.80 × 10−2 S/m. Compared to the conductivity of 1.25 × 10−6 S/m GNS-NR, the improvement was approximately 4 orders of magnitude. The percolation threshold of CNF-GNS/NR composites was significantly lower than that of composites without CNF. Thus, the addition of CNF can reduce the percolation threshold of composites. Using CNF as a biological template to construct a multi-level three-dimensional conductive network in NR can improve the conductive properties of NR composites substantially.