Micro and nanocellulose in electrospinning processes

Cellulose is the most abundant biopolymer on earth. It can be obtained from a lot of plant resources and derived biomass: wood, plants (such as cotton, ramie, sisal, potato tubers, and sugar cane), sea animals (such as tunicates), algae, and bacteria. The interest in this material is given by the fact that it is renewable, sustainable, and biodegradable; these three characteristics are of great interest in recent years to replace materials deriving from fossil fuels. Cellulose is a linear long-chain polysaccharide made up of two anhydroglucose rings linked together with oxygen covalent bond as repeating unit. The structure of cellulose is hierarchical: cellulose molecules align to form microfibrils, which have both crystalline and non-crystalline regions that merge together, and the cellulose microfibrils themselves are aligned and bound together into macrofibrils (or fibril aggregates) by a matrix of hemicellulose and either pectin or lignin. The crystalline part of the cellulose fibrils can be extracted through chemical and mechanical treatments, resulting in cellulose nanocrystals. The excellent characteristics of micro and nano-cellulose fibers, such as their high elastic modulus, has created interest in using them as fillers in polymeric matrices to produce high-performance composites. Micro and nano-cellulose can be introduced as filler also in polymer fibers and fibrous membranes to enhance their properties. An interesting and versatile method to form polymer fibrous structures is the electrospinning. This technology uses electrical forces to produce fibers with nano- or microscale size from polymer solutions. During electrospinning, different parameters could be controlled: the viscosity of the solution, its concentration and surface tension, the voltage applied, the operating temperature and humidity, the geometry of the collector. These parameters influence the morphology of the fibers and their diameters. The obtained fibrous membranes find application in different fields, such as filtration, packaging, tissue engineering, drug delivery. Interestingly a large set of polymers, both natural and synthetic, can be processed by electrospinning. After describing cellulose and the electrospinning method, this work reports the state-of-the-art on the use of micro and nano-cellulose in the electrospinning process. Cellulose fillers have been introduced in different polymer systems (such as polyvinyl alcohol, polyethylene oxide and polycaprolactone) before electrospinning to improve the mechanical features of the obtained fibers and fibrous membranes. Moreover, in the last part of the thesis, a simple experimental work plan on the topic is proposed. In particular, the formation of bio-nano-composite fibrous membranes made of a chitosan matrix and cellulose crystals extracted from cane sugar bagasse as filler is presented. The proposed membranes are completely biodegradable, show good characteristics in terms of mechanical properties and could find application in the food packaging field.