earticle

영어

Natural rubber (NR) based composites reinforced with cellulose nanofibers (CNFs) were prepared using CNFs with different degrees of fibrillation produced by mechanical fibrillation of softwood bleached kraft pulp, and the reinforcing effect of CNFs on NR was studied. The fiber diameter distributions and fiber morphologies of CNFs were estimated by differential centrifugal sedimentation and characterized. To clarify the reinforcing effect of CNFs, NR based composites were reinforced with low amounts of CNFs (5 phr). Although the low-fibrillated CNFs had a small reinforcing effect on NR, the pulling-out of medium-fibrillated CNFs was suppressed, and mechanical properties were improved as well as a decrease in the elongation at break. Meanwhile, the high-fibrillated CNFs improved the tensile strength without decreasing the elongation, although their initial moduli were lower than those of the medium-fibrillated CNFs. Field-emission scanning electron microscopy imaging of fractured surfaces of NR based composites indicated that the branching fibrillated structure of the medium-fibrillated CNFs affected high enhancement of the initial modulus, and the network formed by the high-fibrillated CNFs were involved in improvement of the tensile strength without compromising viscoelastic properties. It can be concluded that the mechanical properties of the NR reinforced with CNFs were determined by the morphologies of CNFs.