Authors: A. Dufresne
Affilation: Grenoble Institute of Technology, France
Pages: 61 - 67
Keywords: polymer nanocomposite, nanoparticle
There has been an explosion of interest in the use of biomass as a source of renewable energy and materials. One focus of this activity has followed from the recognition that, by suitable chemical and mechanical treatments, it is possible to produce fibrous materials with one or two dimensions in the nanometer range from many naturally occurring sources of cellulose. The term nanocellulose is used to cover the range of materials derived from cellulose with at least one dimension in the nanometer range. Owing to its hierarchical structure and semicrystalline nature, nanoparticles can be extracted from naturally occuring cellulose using a top-down mechanically- or chemically-induced deconstructing strategy. Multiple mechanical shearing actions applied to cellulosic fibers release more or less individually the microfibrils. This material is usually called nanofibrillated cellulose (NFC). Production of NFC from wood pulp and various non-wood sources has been reported in the literature. The morphology of constitutive nanoparticles is generally characterized using microscopic techniques. Fig. 1a shows NFC obtained from Opuntia ficus-indica. NFC consists of both individual and aggregated nanofibrils made of alternating crystalline and amorphous cellulose domains. Although image analysis can provide information on fibril width, it is more difficult to determine the length because of entanglement and difficulties in identifying both ends of individual nanoparticles. Indeed, the observation scale for length and diameter are quite different. The width is generally in the range 3-100 nm depending on the source of cellulose, defibrillation process and pretreatment and the length is considered to be higher than 1 μm.