Polymer nanocomposites reinforced with nanoparticles extracted from renewable resources A. Dufresne The International School of Paper, Print Media and Biomaterials (Pagora), Grenoble Institute of Technology (Grenoble INP), CS10065, 38402 Saint Martin d’Hères Cedex, France, alain.dufresne@pagora.grenoble-inp.fr ABSTRACT 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. Keywords: nanocellulose, nanocomposite, cellulose nanocrystal, nanofibrillated cellulose, starch nanocrystal 1 MECHANICAL SHEARING 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. This production route is normally connected to high energy consumptions associated with the fiber delamination. Therefore different pretreatments have been proposed to limit this high-energy input, e.g. mechanical cutting, acid hydrolysis, enzymatic treatment, and introduction of charged groups e.g. through carboxymethylation or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation. The morphology of constitutive nanoparticles is generally characterized using microscopic techniques. Figure 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. Figure 1: TEM from a dilute suspension of (a) NFC obtained after high-pressure mechanical treatment of opuntia ficus-indica fibers [1], and (b) CNC after acid hydrolysis of ramie fibers [2]. 2 ACID HYDROLYSIS A controlled strong acid hydrolysis treatment can be applied to cellulosic fibers allowing dissolution of amorphous domains and therefore longitudinal cutting of the microfibrils. The ensuing nanoparticles are generally called cellulose nanocrystals (CNCs). These nanoparticles occur as high aspect ratio rod-like nanocrystals, or (a) (b) NSTI-Nanotech 2014, www.nsti.org, ISBN 978-1-4822-5826-4 Vol. 1, 2014 61