Chapter 5 - Characterization of Cellulose Nanofiber From Various Tropical Plant Resources

Abstract

Cellulose nanofiber (CNF) is an emerging nanomaterial which has gained attention from researchers and industries due to its versatility and potential applications in various fields. As a tropical country, Malaysia has various plant resources which can be used for CNF production. In this chapter, the potential of CNF production from three different tropical plant resources is evaluated: Napier grass, Kenaf core, and Eucalyptus cellulose pulp. Napier grass and Kenaf core were pretreated for cellulose extraction, while Eucalyptus pulp (obtained from a pulp and paper company in Thailand) was used as is. The pretreatment of Napier grass and Kenaf core was conducted using 50wt% totally chlorine-free (TCF) solvent and 6wt% KOH with the aim of removing lignin and hemicellulose, respectively. Cellulose samples obtained from treated Napier grass and Kenaf core and untreated Eucalyptus pulp were then soaked in distilled water for 3 days prior to nanofibrillation by a wet disk mill (WDM). Fourier transform infrared (FTIR) analysis demonstrated that the lignin and hemicellulose in Napier grass and Kenaf core were completely removed after the pretreatment process. Furthermore, no structural changes occurred to CNF after WDM compared to the nonfibrillated sample, as shown by the FTIR spectra. In terms of size reduction, field-emission scanning electron microscopy micrographs exhibited the formation of CNF with diameter sizes less than 100nm for all samples after the cellulose samples were ground for five cycles using a WDM. There was slight reduction in crystallinity index (CrI, %) and thermal stability after WDM. Meanwhile for Eucalyptus pulp, CNF with diameter size less than 100nm was only formed after 10th cycle of WDM. The productivity of CNF from Eucalyptus pulp was also lower (1.43kgh−1) compared to Napier grass and Kenaf core (1.58 and 1.54kgh−1, respectively). This can be explained by the complex structure of cellulose from woody Eucalyptus compared to the nonwoody Napier grass and Kenaf core. Overall, this research shows that CNF can be produced from tropical woody and nonwoody plant resources using a WDM and the characteristics of the CNF produced at the end of the milling process were similar for all plant sources.