Micro/nanofibrilas de celulose obtidas a partir da madeira de Erythrina poeppigiana

Abstract

Erythrina poeppigiana is a tree species used in agroforestry systems for the shade of Theobroma cacao crops. New cultivars and more advantageous production models, from an economic and environmental point of view, led to the abandonment of crops cultivated under the erythrin canopy, resulting in the supply of a large amount of Wood of the genus. Considering that Erythrina spp. wood does not have the characteristics recommended for traditional applications, this work proposed to evaluate the feasibility of using E. poeppigiana wood for the production of cellulose micro/nanofibril (CMF/CNF). Preliminarily, tests were carried out to determine the basic density and mechanical strength of the wood. Particles of E. poeppigiana wood were treated with sodium hydroxide (NaOH) and mechanically fibrillated to obtain CMF/CNF suspensions. Analyses were carried out to determine the chemical and physical composition of the particles before and after treatment. The natural and treated particles were submitted to morphological analysis to evaluate the effects of the alkaline treatment. Tests were performed to determine the solids content, viscosity, turbidity and stability of the suspensions, in addition to the analysis of the images obtained by ultra- high resolution scanning electron microscopy (MEV/UHR). With the suspensions, films were produced by the casting method, which were evaluated for their physical, optical, barrier and mechanical properties. To compare the results, tests were performed on samples of CMF/CNF films of unbleached cellulosic pulp of Eucalyptus sp. The Wood of E. poeppigiana presented a basic density of 0.299 g/cm 3 , being classified as low density. Regarding the mechanical properties of the wood, strength (MOR) and stiffness (MOE), the average in the static flexural tests was 43.11 MPa and 4.96 GPa, respectively. The analysis of the chemical composition proved the efficacy of the treatment used by showing the reduction in the percentage of ash and lignin. This efficacy was also observed in the images obtained by the scanning electron microscope (MEV), which showed the swelling of the fibers due to the modification suffered on their surface. The MEV-UHR images of E. poeppigiana suspensions proved the formation of CMF/CNF, with a predominance on the micrometric scale (60.22%), but also with a significant presence on the nanometric scale (39.88%). The suspensions of E. poeppigiana showed solids contents of 1.33%, viscosity of 707.00 cP and turbidity of 140.6 NTU. The films presented average values of thickness, grammage, bulk density, and porosity of 37.4 μm, 26.06 g/m 2 , 0.69 g/m 3 , and 54.92%, respectively. High oil resistance was found for kit 12 solution, with a water vapor transmission rate of 868.23 g/m 2 .day and water vapor permeability of 5.71 g.mm/dia.m 2 .kPa. The solubility in water was 6.74% and the contact angle and wettability obtained mean values of 71.59 o and 0.29 o /s, respectively. The film samples submitted to the tensile strength test obtained average values of 29.44 MPa and Young's Modulus of 3.28 GPa. The puncture resistance was 3.19 N mm - 1 . The results demonstrate that, despite the low density and mechanical strength, E. poeppigiana wood can be a viable alternative for the production of CMF/CNF.