Facultad Regional San Francisco
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Item Mechanistic insight into hydroxy‑methylation of hardwood kraft lignin(2024-09-24) Peralta, Micaela; Pajer, Nicolò; Crestini, Claudia; Nicolau, Verónica V.In view of developing upcycling strategies for hardwood Kraft lignin, hydroxymethylation of Eucalyptus Kraft lignin under alkaline conditions (pH 9 and 11) at different temperatures (50 °C and 70 °C) was studied in the present effort with the double objective of optimizing the reaction conditions and understanding the functionalization mechanism of C5 in either terminal or internal guaiacyl units during hydroxy-methylation. Formaldehyde consumption was estimated via titration of the oximated free formaldehyde; the hydroxy-methylation degree under the reaction was estimated by calculating the ratio in Condensed hydroxyl/Guaiacyl (Condensed OH/G-OH) via a new difference UV-spectroscopy. The reliability of the difference UV-method results for the analyses of the hydroxy-methylated lignins was statistically analysed and compared with that of vacuum-dried and sonicated samples. Hydroxy-methylated samples were then fully characterised by NMR (31P and HSQC) and GPC. The reaction temperature of 50 °C, pH 11, and period time of one hour resulted as the optimal conditions for the hydroxy-methylation, preventing the side-reactions leading to the formation of dimethylene-glycol addition products.The 31P and 1H–13C HSQC NMR revealed the absence of undesirable formaldehyde Cannizzaro by-products and the lack of hydroxymethyl groups in the aliphatic side chain under the studied conditions. GPC analyses, comparing two methodologies, revealed increases in molar mass of the hydroxy-methylated samples upon the formaldehyde addition. The selective hydroxy-methylation at the C5 guaiacyl site demonstrates that Eucalyptus Kraft lignin is as a promising candidate for resolproductionItem Supernucleation dominates lignin/poly(ethylene oxide) rystallization kinetics(2022-08) Taverna, María E.; Altorbaq, Abdullah S.; Kumar, Sanat K.; Olmedo-Martínez, Jorge L.; Busatto, Carlos Alberto; Zubitur, Manuela; Mugica, Agurtzane; Nicolau, Verónica V.; Estenoz, Diana; Müller, Alejandro J.The effect of lignin nanoparticles (LNPs) on the crystallization kinetics of poly(ethylene oxide) (PEO) is examined. Lignin from spruce and ionic isolation was used to prepare LNPs with a number-averaged diameter of 85 nm (with a relatively large polydispersity) by an ultrasonication method. PEO-based nanocomposites with four different LNP contents (5, 10, 15, and 20 wt %) were prepared and subject to isothermal and nonisothermal crystallization protocols in a series of experiments. Scanning electron microscopy (SEM) images showed welldispersed LNPs in the crystallized PEO matrix. The incorporation of LNPs exponentially increases nucleation density at moderate loadings, with this trend apparently saturating at higher loadings. However, the spherulitic growth rate decreases monotonically with LNP loading. This is attributed to the substantial PEO/LNP affinity, which impacts chain diffusion and induces supernucleation effect (with efficiencies in the order of 200%), but leads to slower growth rates. The overall crystallization kinetics, measured by the DSC, shows faster nanocomposite crystallization rates relative to the neat PEO at all LNP contents examined. This indicates that the supernucleation effect of LNPs dominates over the decrease in the growth rates, although its influence slightly decreases as the LNP content increases. The strong hydrogen-bonded interactions between the LNPs and the PEO are thus reminiscent of confinement effects found in polymer-grafted NP nanocomposites (e.g., PEO-g-SiO2/ PEO) in the brush-controlled regime.Item Development of a bio-based high pressure laminate (HPL) by partial replacement of phenol with hardwood kraft lignin: design, optimization and scaling-up(GEP-SLAP, 2022-05) Peralta, Micaela; Nicolau, Verónica V.This work involved the design, optimization and scaling-up of the Hx process of a eucalyptus KL for resol synthesis and HPL production. Variables such as pH, temperature, and order of conditioning of reagents were studied during the laboratory optimization of the Hx to favor dissolution and increase KL reactivity. Scaling-up was performed at Centro S.A., San Francisco, Córdoba, Argentina. The hydroxymethylated KL (HL) was employed for the substitution of 30 wt% P in resol synthesis. The lignin-phenol-formaldehyde (LPF) and conventional PF resins were characterized and employed for the industrial impregnation of Kraft-type paper and subsequent curing. Tensile and flexural tests of HPL were performed. Also, boiling water resistance test was performed.Item Determinación de grupos hidroxilo fenólicos reactivos en lignina Kraft de madera dura por titulación acuosa potenciométrica(AJEA- Actas de Jornadas y Eventos Académicos de UTN, 2023-12) Peralta, Micaela; Dobler, Santiago; Lesta, Mateo Ariel; Nicolau, Verónica V.Las ligninas Kraft son polímeros naturales polifenólicos de estructura compleja cuya baja reactividad puede sortearse mediante la activación por hidroximetilación con incorporación de grupos hidroximetilo reactivos necesarios en la fabricación de poliuretanos y adhesivos fenólicos. El trabajo experimental consistió en la optimización de una técnica potenciométrica para la determinación de grupos hidroxilo fenólicos y su monitoreo durante la funcionalización de una lignina de madera dura por hidroximetilación a temperaturas de 50 y 70 °C y pH 9 y 11. La optimización de la técnica potenciométrica permitió una reducción del 38 % en el tiempo de pretratamiento total de la muestra. La lignina hidroximetilada a pH 11 y 70 °C exhibió la mayor conversión (31 %) de grupos hidroxilo fenólicos.Item Superficies Sólidas a partir de Resinas Poliéster Insaturadas Modificadas con Aceite de Ricino Maleinizado: Biodegradación por el Ataque de Hongos Filamentosos(Universidad Tecnológica Nacional, 2017-03-30) Bernard, Mariana del Valle; Nicolau, Verónica V.; Estenoz, DianaDebido al impacto ambiental causado por el uso creciente de polímeros derivados del petróleo, existe un gran interés en el desarrollo de nuevos polímeros basados en fuentes renovables. Se busca diseñar materiales que exhiban buenas propiedades finales durante su uso y que presenten biodegradabilidad al final de su vida útil. En ese sentido, el aceite de ricino puede ser funcionalizado y empleado como sustituto parcial de resinas poliéster insaturadas en la producción superficies sólidas. El trabajo experimental involucro la síntesis y caracterización del aceite de ricino maleinizado, la degradación de los polímeros por hidrólisis química y enzimática de Aspergillus niger y Alternaria sp por un período de 230 días, y la caracterización de los polímeros (antes y después de la degradación) y de los compuestos de degradación por técnicas gravimétricas y GC-masa, respectivamente.Item Microparticles based on ionic and organosolv lignins for the controlled release of atrazine(Journal of Hazaourdos Materials, 2018-07-02) Taverna, María E.; Busatto, Carlos Alberto; Lescano, Maia Raquel; Nicolau, Verónica V.; Zalazar, Cristina; Meira, Gregorio; Estenoz, DianaLignins are natural polymers of the lignocellulosic biomass. Nowadays, there is a growing interest in developing value-added products based on lignins due to their renewability, low cost and abundance. In this work, lignin microspheres from organosolv and ionic isolation processes were prepared for the controlled release of atrazine. Microspheres were prepared by the solvent extraction/evaporation technique. The controlled release of atrazine from organosolv and ionic lignins microparticles was studied in water. Mobility experiments were performed in an agricultural soil from Argentina. The results showed that microparticles prepared using dichloromethane as the dispersed phase were spherical, while lignins dispersed in ethyl acetate produce irregular microparticles. Organosolv lignin microparticles presented higher encapsulation efficiency for all herbicide loads. About 98% and 95% of atrazine was released in 24 and 48h approximately from organosolv and ionic lignin microparticles, respectively. The release profiles of atrazine from both lignin microparticles were not affected by the herbicide load. Atrazine mobility experiments in soil showed that about 80% of free atrazine was leached in 37 days, while 65.0% and 59.7% of the herbicide was leached from ionic and organosolv lignin microparticles, respectively. Thus, atrazine-loaded microparticles could reduce leaching compared to a commercial formulation of free atrazine.Item Mechanical evaluation of laminates based on phenolic resins using lignins as partial substitutes for phenol(Bioresources, 2015-10-28) Taverna, María E.; Ollearo, Rocío; Morán, Juan; Nicolau, Verónica V.; Estenoz, Diana; Frontini, PatriciaReducing the consumption of phenol during synthesis of phenolic resins is of great technological and scientific interest because of its economic and environmental implications. In this work, the use of hydroxymethylated lignins as a partial replacement for phenol in resol phenol-formaldehyde resins used for the production of decorative laminates was experimentally studied. The work involved: i) the industrial synthesis of traditional and modified resols with 10%w/w of sodium lignosulfonate and kraft-type lignin; ii) the industrial impregnation of kraft-type paper with the produced resins; iii) the production of laminates on both laboratory and industrial scales; and iv) the measurement of their final properties. The mechanical performance of the laminates was evaluated via the determination of the Young modulus, bending strength, biaxial impact strength, and Mode-I interlaminar fracture toughness. The (modified and traditional) laminates exhibited statistically significant differences in mechanical properties. However, the partial lignin replacement did not produce effects that were detrimental effects to the overall performance of the decorative laminates.