RT Dissertation/Thesis T1 Biotechnology applied to the modification of lignocellulosic materials : improvement of the surface properties and manufacturing of biocomposites for 3D printing T2 Biotecnología aplicada a la modificación de materiales lignocelulósicos : mejora de las propiedades superficiales y elaboración de biocomposites para impresión 3D A1 Martinez Filgueira, Daniel K1 3312.13 Tecnología de la Madera AB Wood and lignocellulosic fibers are renewable raw materials, with a high availability, a relatively low density and interesting physico-mechanical properties. These characteristics confer to lignocellulosic materials multiple industrial applications. From a chemical point of view, wood is mainly composed of cellulose, hemicellulose and lignin. Both cellulose and hemicellulose posses a high amount of hydroxyl groups which gives the lignocellulosic fibers a high hydrophilicity. This characteristic leads to a high affinity of the lignocellulosic fibers with water, which facilitates the attack of microorganisms such as fungi and bacteria. At the same time, the high hydrophilicity of the wood fibers causes problems of dimensional stability and hinders a good chemical compatibility between the fibers and hydrophobic materials such as plastics. Therefore, lignocellulosic materials must be modified in order to improve their chemical and biological properties.There are different chemical and physical treatments to modify lignocellulose fibers. However, most of these treatments involve the use oil-derived compounds and/or require large amounts of energy. A sustainable end eco-friendly alternative are biotechnological treatments. The laccase is a lignolytic enzyme that has the ability to oxidize, among others, phenolic substrates. This fact allows the functionalization of substrates such as lignin by the enzymatic grafting of compounds which provide certain chemical and biological properties. By this way, it is possible to modify the surface properties of wood fibers without using large amounts of energy and in a completely environmentally friendly way. The compounds that will be used to functionalize the fibers will be compounds of natural origin (condensed tannins from radiata pine bark) and synthetic ones (gallates).Given the physical properties, as well as its high availability and biodegradability, lignocellulosic fibers are used as a reinforcing material in the manufacturing of biocomposites. Biocomposites are materials composed of a matrix (usually polymers) reinforced with fibers of natural origin. This allows a substantial improvement of the mechanical properties and, at the same time, the mass of the biocomposite is reduced, which directly affects the production costs. However, the main problem biocomposites manufacturing is the poor chemical compatibility between the polymer matrix (hydrophobic) and the wood fibers (hydrophilic). Such low interfacial adhesion leads to structural failure zones within the biocomposite and has a remarkable effect in their mechanical properties. The hydrophobicization of the lignocellulosic fibers by means of the enzymatic grafting of gallates enables the improvement of the interfacial adhesion between the matrix and the fibers, which will have a direct impact in the improvement of mechanical properties and the reduction of the water absorption of the biocomposites.On the other hand, one of the most promising manufacturing systems is 3D printing, which allows the production of three-dimensional objects from biocomposite filaments. The possibility of designing complex structures, customizing the product and reducing time and material makes possible to produce objects for very specific applications (medical, aerospace, automotive, etc.). Therefore, 3D printing offers a new perspective for the valorization of lignocellulosic materials. LK http://hdl.handle.net/11093/1080 UL http://hdl.handle.net/11093/1080 LA eng NO Fondos FEDER | Ref. 09TMT012E DS Investigo RD 11-feb-2025