Synthesis of cellulose esters for further use in the synthesis of polyurethanes

• Grant number: 19/00884-2
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): April 01, 2019
• Effective date (End): November 30, 2020
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal researcher: Elisabete Frollini
• Grantee: Claudia Santana Gonçalves Ferreira
• Home Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The use of lignocellulosic biomass as an input for the production of different materials meets the expectations regarding the use of renewable resources as raw materials for the production of new materials. Lignocellulosic fibers are mainly composed of cellulose, hemicelluloses, and lignin, with cellulose being the most abundant vegetal polymer in nature. In the present project will be synthesized (in homogeneous medium, using the solvent system Dimethylacetamide / Lithium chloride) and characterized, cellulose esters with relatively long chains (as butanoates and hexanoates) linked to the carbonyl of the ester group, from the reaction of microcrystalline cellulose with anhydrides.This cellulose was chosen because it has relatively short chains, which is suitable for the second part of the project, in which the esters will be used as reagents in polyurethane synthesis. The stoichiometry of the reaction will be adapted to obtain esters with a degree of substitution (DS) around 1.0. The cellulose will be characterized by infrared spectroscopy - Fourier transform (FTIR), average viscometric molar mass, Scanning Electron Microscopy , crystallinity (X ray diffraction). Characterization of the esters will correspond mainly to FTIR and Proton Nuclear Magnetic Resonance (1H NMR, for the determination of the DS of the esters).The second part of the project will consist of using different proportions of previously synthesized cellulose esters, which, having a DS around 1.0, will have around two non-acylated hydroxyls per glycosidic unit, and available to act as polyols in the synthesis of polyurethanes. The hydrocarbon chain bonded to the carbonyl group of the ester may act as an internal plasticizer of the films obtained from the synthesized polyurethanes. The castor oil (CO, whose main component is ricinoleic acid) will be used as an additional source of hydroxyl, and also to act as a dispersing agent of the cellulose esters in the reaction medium, because the reaction will occur in the absence of solvents.Also, a diisocyanate, initially the polymeric diphenylmethane diisocyanate (PMDI), will be used as the reagent. The reaction will initially take place in a stirred flask at room temperature, and from the observation of viscosity that allow the viscous medium to be spread in a glass plate, this will be done, which will allow film formation while continuing the reaction. The reaction will be monitored via FTIR, by decreasing the intensity, and later disappearance, of the band referring to the isocyanate group, which will be consumed during the reaction. Monosubstituted cellulose esters, with relatively long hydrocarbon chains bounded to the ester group, were selected as one of the reactants (polyol), aiming for these chains to act as an internal plasticizer of the prepared films.