Evaluation of grinding efficiency for the preparation of cellulose nanofibril treated by electron beam irradiation

Abstract

This study investigated the effect of electron beam irradiation on the grinding efficiency of softwood and hardwood bleached kraft pulp (SwBKP and HwBKP, respectively) for the preparation of cellulose nanofibrils (CNFs). The pulps were irradiated with a 50 kGy electron beam and subsequently refined, followed by micro-grinding. During the micro-grinding, the grinding efficiency was evaluated by measuring the required number and the time of grinding. The fiber widths of the CNFs were measured by transmission electron microscopy and their properties, including low-shear viscosity, particle size, crystallinity, were also analyzed. When the electron beam irradiated the BKPs, the number and the time of grinding decreased significantly. The effect of electron beam irradiation on the grinding efficiency was greater for SwBKP than for HwBKP. All of the CNFs showed fiber widths smaller than 100 nm, indicating that they were ground to nano-scale by the irradiation and the micro-grinding. The viscosity increased, and the particle size and the crystallinity of the CNFs decreased as the number of micro-grindings increased. However, the differences in particle size and crystallinity between irradiated and non-irradiated CNFs were not statistically significant. Therefore, electron beam irradiation is concluded to improve the grinding efficiency of BKPs for the preparation of CNFs.