Cellulosic nanofibrils from eucalyptus, acacia and pine fibers

The strong, environment-friendly and abundantly available cellulose nanofibril (CNF) is a very interesting building block for various types of material. To facilitate the industrial use of the fibrils, their liberation from the wood fiber wall needs to be improved particularly since the process requires a substantial amount of mechanical energy. In this work, the influence of wood species on fiber wall disintegration has been studied. Fibers from eucalyptus, acacia and pine were enzymatically treated and then mechanically fibrillated by an earlier reported process. The nanofibril yield, evaluated by centrifugation, was then compared to the charge density, wood polymer composition and cellulose DP of the original fibers. The results indicate that the CNF yield of the process increases with the increase of charge density of the fibers. It was also found that the charge density of the CNFs was higher than that of the original fibers. In the case of films produced from uncentrifuged dispersions, the results indicated improved mechanical properties with increasing CNF yield. Eucalyptus, with the highest yield, showed the highest Young's modulus and the highest stress at break of the investigated pulps, whereas the acacia showed the greatest strain at break. However, in the case of the films produced from fibrils after centrifugation, the same trend could not be observed. In this case, the pine showed the highest Young's modulus. The transparency of the films was however, as expected, greater as a result of the centrifugation procedure for all the investigated pulps.