Obtenção e caracterização de nanopartículas de lignina kraft e incorporação em aerogéis de nanofibrilas de celulose

Abstract

Lignin is a macromolecule located on the secondary wall of plants and is a natural source of aromatic compounds. It is obtained in large quantities as a co-product of the paper and cellulose industry, during the cooking of the wood to obtain the pulp. In Brazil, industrial Kraft lignin is obtained in large quantities from the Kraft pulping process. The advantages of lignin are related to its antimicrobial and antioxidant properties, UV protection capacity and as raw material in the preparation of various types of materials and inputs. Despite all these possibilities, millions of tons of lignin are still burned for power generation in the pulp and paper mills. Studies show that some of the properties of lignin can be improved or enhanced if this material is nanoparticulate. Thus, the use of lignin nanoparticles instead of the common material would bring numerous advantages such as increased surface area, improved amphiphilic character, better dispersion in water and greater antioxidant activity. Some methodologies have been studied in order to produce lignin nanoparticles in order to cause less environmental impacts. In this context, this study aimed to develop an environmentally friendly methodology for obtaining Kraft lignin nanoparticles and incorporating them into cellulose nanofibril aerogels. In the first part of this work, a literature review about lignin, nanoparticulate lignin and application in composites was carried out. The second part presents an article proposed for publication. The nanoparticles were obtained using a sonicator. The methodology used in the study was effective in obtaining spherical nanoparticles, with an average diameter of 190 nm, presenting regular size distribution and without altering the chemical structure of lignin. The nanoparticle suspension remained stable for up to four months. Aerogels prepared with 6% lignin nanoparticles and cellulose nanofibrils showed low density, high porosity and improved mechanical properties and thermal stability when compared with material without lignin nanoparticles in their composition.