Materials based on raw materials deriving from renewable sources

Abstract

The topic of this project, the use of renewable raw materials from diverse processes, has attracted worldwide interest. This issue has assumed even greater importance in recent years due to large expansion that can be envisioned for biorefineries that produce bioethanol. It may be expected that diverse lignocellulosic fibers will be grown to a greater extent than currently, particularly in Brazil due to the availability of both, land and water. The projects currently under development, which will continue in the proposed project, have considered lignocellulosic fibers obtained from plants with short growth cycles that are abundant in the country. In recent decades, great efforts have been made toward the development of polymer materials from lignin, with the goal of finding new alternatives to products originating from petrochemicals. Currently, the use of lignin assumes a greater significance due to the fact that it is a byproduct of biorefineries that produce bioethanol from the cellulose found in lignocellulosic fibers. The presence of phenolic aromatic rings enables their use as macromonomers in the preparation of phenolic polymers, and the presence of hydroxyl groups (in this case both in the lignin and cellulose) allows their use in the preparation of polyurethanes, which is being developed by the proponent and is part of this proposal. In addition to the benefit of using renewable raw materials, both in the preparation of the matrix (using lignin) and in reinforcement (using lignocellulosic fibers), it is expected that fiber-matrix adhesion will be favored due to the presence of similar functional groups in the matrix and fibers, which contain typical lignin structures. To further increase fiber-matrix compatibility (and therefore to intensify interaction at the fiber-matrix interface), fibers are also subjected to treatment in pursuit of adsorption of fiber-matrix compatibilizing agents (derived from natural sources). In addition, studies have been developed for the preparation of cellulose esters, considering esters with different chain lengths. With regard to applications, it is intended to use the cellulose esters to obtain films and biocomposites-type films that will be prepared from one of the solvent systems used in the synthesis of these esters, i.e., LiCl/DMAc. The biocomposites-type films will be prepared from mixed solutions of esters and cellulose so that the potentially possible supramolecular structures generated by the self-organization of cellulose chains in this medium act to reinforce the matrix of esters. Finally, continuous nanoscale fibers (for application in biocomposites) will be obtained via electrospinning using the major components of lignocellulosic fibers (cellulose and lignin), among other raw materials. The characterization of the raw materials and their derivatives, will occur via X ray Diffraction (XRD) Nuclear Magnetic Resonance (1H, 13C, 31P, NMR solution or solid, depending on the sample), thermal analysis [Thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC)], scanning electron microscopy (SEM) and transmission electron microscopy (TEM), impact and flexural strength (in the case of composites). Dynamic-mechanical thermal analysis (DMTA) can be highlighted as an important technique to be used in the characterization of composites, films and biocomposites-type films, for via this technique storage and loss moduli can be obtained, as well as tensile strength (in the case of films), thus generating important information about mechanical properties of materials. (AU)