Síntese e caracterização do sulfato de acetato de celulose, obtido do bagaço de cana-de-açúcar, para aplicação como aditivo na construção civil

Abstract

The cellulose of sugarcane bagasse was chemically modified for producing cellulose sulfate acetate, which was tested as an additive in mortars of Portland cement (CPV ARI) in the civil construction. The material was produced by simultaneous acetylation and sulfonation, and besides cellulose sulfate acetate, two byproducts were generated, which presented different solubility in water. The obtained materials had been characterized by Infrared spectroscopy (IV), and revealed that only one of the derivatives showed the characteristic band of sulfate groups (807 cm-1) in the infrared spectrum, which was cellulose sulfate acetate. This material was then characterized by determination of the degree of substitution of acetyl groups by chemical route (DSacetyl), determination of the degree of substitution of sulfate groups (DSsulf) by Elemental Analysis, Nuclear Magnetic Resonance (13C-NMR), X-ray Diffraction, determination of reduced viscosity and Thermogravimetric Analysis (TGA). The results have shown that the cellulose derivative showed a DSacet of 2.7 and DSsulf of 0.063. Compared to the 13C-NMR spectrum of cellulose acetate (derivative that occurs only in the incorporation of acetyl groups), the presence of sulfate groups in the sample of cellulose sulfate acetate shifted the position of C6 peak for lower field in 13CNMR spectrum, due to not shield carbon caused by the incorporation of electronegative groups. According to the diffractogram obtained to the cellulose sulfate acetate, it appears that the sample sulfoacetylated presents an X-ray diffraction pattern mainly amorphous, mainly due to the presence of a pronounced halo at about 2θ = 22 °. By measuring the reduced viscosity of the solution of cellulose sulfate acetate, it was found that the presence of ionic sulfate groups in the sample is the causes to reduced viscosity increase to more dilute concentrations (below 1 mg/mL). In the synthesis of cellulose sulfate acetate is produced a polyelectrolyte that due to the presence of sulfonic groupsmay be able to act as an additive for mortars in the construction industry due to its high solubility in water. The evaluation of cellulose sulfoacetate as additive to mortars was based on results of fluidity, mechanical strength to compression of hardened mortar and potential resistance of adhesion strength. The best results were obtained for the polymer/cement ratio of 0.60% with which it was achieved an increase of 13.80% in consistency and 21.05% on the potential resistance of adhesion strength, while the strength to compression remained nearly constant compared to the reference without additive. Then, it was possible to synthesize the sulfate cellulose acetate obtained from sugarcane bagasse and apply it as additive for mortars in civil construction.