RESUMO O presente estudo contempla a aplicação de nanopartículas magnéticas de ferrita de manganês MnFe2O4 (NPM) modificadas com poliestireno sulfonado (PSS) na adsorção de íons de Pb (II) para fins de tratamento de água contaminada. A funcionalização da nanopartícula com o polímero objetivou aumentar a capacidade de adsorção e incluir a utilização de material reciclável em função da importância ambiental. Os adsorventes foram caracterizados por espectroscopia no infravermelho por transformada de Fourier, espectroscopia de energia dispersiva por raio X, difração de raios X, microscopia eletrônica de varredura, microscopia de força atômica, análise elementar, análise termogravimétrica, ponto de carga zero, área superficial e porosidade. O PSS representou 14% da massa das nanopartículas magnéticas de MnFe2O4 funcionalizadas com o poliestireno sulfonado (NPM-PSS) e o teor de grupos sulfônicos foi de 17,18%. Os modelos de isoterma de Freundlich e cinético de pseudossegunda ordem apresentaram maior acurácia pelos dados experimentais de adsorção dos íons Pb (II) pela NPM-PSS, cuja capacidade de adsorção das nanopartículas variou de 6,254 a 7,535 mg g−1.

ABSTRACT The present study contemplates the application of magnetic nanoparticles of manganese ferrite MnFe2O4 (NPM) modified with sulfonated polystyrene (PSS) in the adsorption of Pb(II) ions for the purpose of treating wastewater. The functionalization of the nanoparticle with the polymer aimed to increase the adsorption capacity and include the use of recyclable material due to its environmental importance. Adsorbents were characterized by Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, elemental analysis, thermogravimetric analysis, point of zero charge, surface area, and porosity. PSS represented around 14% of the mass of magnetic nanoparticles of MnFe2O4 functionalized with sulfonated polystyrene (NPM-PSS) and the content of sulfonic groups was 17.18%. The Freundlich isotherm and pseudo second order kinetic models showed greater accuracy by the experimental data of adsorption of Pb (II) ions by NPM-PSS, whose adsorption capacity of nanoparticles ranged from 6.254 to 7.535 mg g−1.

Abstract Cellulose nanocrystals (CNCs) can improve the mechanical properties of dental resins. However, there is a deficiency of information about the behavior of physical properties of resins after this addition. The purpose was to evaluate the characterization and physical properties of hard chairside reline material modified with CNCs (0.25%, 0.5%, 0.75% or, 1.0%). Addition of CNCs at 0.5%, 0.75% and 1% increased Vickers hardness; 0.75% decrease surface free energy; 0.75% and 1% showed similar to control on the surface roughness. The simple and straightforward approach of adding CNCs, a renewable material, provides good potential for its future practical application as it has shown promise with increasing hardness. It means that the incorporation of CNCs into this denture reline resin could improve the abrasion resistance of this material, which is desirable in the long term.

Abstract This study evaluated the effects of three chemical pretreatments of biomass sorghum (BS): dilute alkaline (PTA1 and PTA2), dilute acid (PTB1 and PTB2) and alkaline hydrogen peroxide (PTC1 and PTC2) in the enzymatic hydrolysis and ethanol production. Among the six investigated conditions, the pretreatment with 7.36% H2O2 (PTC2) was the most efficient in the lignin removal and preservation of the polysaccharide fraction. After the enzymatic hydrolysis, increases in the glucose and xylose concentrations were observed in the pretreated BS hydrolysates, mainly in PTB1 and PTC1. All the hydrolysates obtained low concentrations of inhibitors. In the alcoholic fermentations with Pichia stiptis, the greatest ethanol yield was obtained in PTB1 hydrolysate (3.84 g L-1), corresponding to 16.15% of yield. The highest ethanol yield in PTB1 hydrolysate can be justified by the maximum concentration of xylose obtained in this hydrolysate, demonstrating the potential of P. stiptis in the fermentation of pentose to ethanol. The results indicated that biomass sorghum is an alternative lignocellulose source with potential for the production of second generation ethanol, opening up prospects for additional studies.

Abstract In the present study, catalytic activity of dense, porous, electrospun membranes of polysulfone (PSF) and polysulfone with sulfonated polystyrene (PSF_PSS) have been evaluated in reactions of esterification of oleic acid with methanol, in times that varied from 10 to 480 minutes. Conversion to biodiesel has been confirmed by FTIR and quantified through gas chromatography. The results showed the catalysts used were effective in the esterification reaction studied and the PSF_PSS electrospun membrane has presented the best conversion to methyl oleate, reaching 70.5% in a 10-minute reaction and 95.8% in a 240-minute reaction, when methanol:oleic acid molar ratio of 10:1, 5% of catalyst and temperature of 100 °C were used. Considering the performance of solid catalysts described in literature, mainly related to reaction times and conversion of the process, this study reveals a promising feasibility of using electrospun membranes of PSF_PSS for developing a heterogeneous acid catalyst aimed to biodiesel synthesis.

Vegetable fibres have been shown to be promising as reinforcement in composites because they are abundant, renewable, and low cost. However, the fibre-matrix interaction can be damaged by dimensional variation of vegetable fibres, due to moisture variations. The alkaline medium of cementitious matrix is aggressive to natural fibres, compromising their durability. The aim of this study was to modify sisal fibres (Agave sisalana) by esterification with acyl chlorides to improve their stability and compatibility with the cementitious matrix in order to optimize the performance and durability of composites. The esterified fibres were characterized by moisture absorption, tensile tests, Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) and the composites by bending tests and SEM. The results showed that esterification changed both the morphology and physical properties of sisal fibres. The composite produced using esterified fibres with octanoyl chloride maintained the properties of 28 to 90 days of age, which represented an improvement in the fibre stability compared to natural fibre composite.

Flaxseed gum (FG)-based films were developed with the addition of glycerol as a plasticizer and glutaraldehyde as a crosslinking agent. HCl was added to improve crosslinking and decrease the hydrophilicity of the matrix. Different cellulose nanocrystal (CN) amounts were used as reinforcements in the optimum FG formulation. The crosslinking process at pH 3.5 led to a lower solubility of FG in water (from 100% to 53%) and an increase in thermal stability (from 160 ºC to 209 ºC). FTIR analysis confirmed a reduction in the -OH band due to crosslinking between the hydroxyl groups of FG. A diffuse diffraction pattern was observed for all FG films. The addition of 4% w/w of CN contributed to reduction of water solubility (from 53% to 20.8%) and absorption (from 21.9% to 6.8%). Finally, an improvement was observed in the tensile mechanical properties in the nanocomposites, showing satisfactory results for the proposed formulations, mainly with 8% w/w of CN added to the matrix. Overall, this study demonstrated that FG/CN nanocomposites are promising materials to be use as a sustainable biopolymer for application as bioplastics.

Resumo Este trabalho apresenta estudo da esterificação de fibras de bucha vegetal (Luffa cilyndrica) para verificar o desempenho delas na matriz cimentícia. As reações de esterificação foram realizadas com os agentes modificadores cloreto de octanoíla, cloreto de lauroíla e cloreto de estearoil, usando tolueno como solvente e piridina como catalisador. As fibras foram caracterizadas por ensaios de tração direta, microscopia eletrônica de varredura (MEV) e absorção de umidade. Foram produzidos compósitos com as fibras sem tratamento e tratadas com cloreto de octanoíla, tendo estas apresentado os melhores resultados, com redução de 65% na absorção de umidade, 40% na resistência à tração, e aumento de 67% no módulo de elasticidade. Os resultados do ensaio de flexão dos compósitos indicaram que a tenacidade da ordem de 0,70 kJ/m2 não se alterou significativamente e que houve aumento de cerca de 20% no módulo de ruptura (6,64 MPa) e no módulo de elasticidade (15,10 GPa) dos compósitos reforçados com as fibras modificadas em relação aos reforçados com as fibras sem tratamento. As melhores propriedades mecânicas do compósito com as fibras tratadas indicam que o tratamento proposto pode ter melhorado o desempenho das fibras vegetais como reforço da matriz cimentícia.

Abstract This paper discusses the esterification of sponge gourd fibres (Luffa cilyndrica) to reinforce the cementitious matrix. The esterification reactions were performed with the modifying agents octanoyl chloride, lauroyl chloride and stearoyl chloride, using toluene as solvent and pyridine as catalyst. The fibres were characterised through tensile tests, scanning electron microscopy (SEM) and moisture absorption. Composites were produced with untreated and treated fibres with octanoyl chloride, which yielded the best results, with a 65% reduction in moisture absorption, 40% in tensile strength and 67% increase in the elasticity modulus. The results of the composites bending test indicated that a toughness of 0.70 kJ/m2 did not change significantly and there was an increase of about 20% in the rupture modulus (6.64 MPa) and the elasticity modulus (15.10 GPa) of the composites reinforced with treated fibres compared with those reinforced with untreated fibres. The best mechanical properties of the composites with treated fibres indicate that the proposed treatment may have improved the performance of sponge gourd fibres as a reinforcement of the cementitious matrix.

Abstract This study evaluated the effects of the incorporation of a new additive to asphalt cement oil (CAP). A polyol product was obtained through the oxypropylation reaction of sugarcane bagasse. This polyol was polymerised with pyromellitic anhydride in order to obtain a polyester (BCP) to test its suitability in terms of the material properties to be applied as additives. FTIR spectra of the polymerised material (BCP) confirmed the occurrence of chemical modification due to the appearance of a new band at 1750 cm-1, characteristic of ester groups. The TGA data showed that the BCP product had higher thermal stability than the polyol. According to the softening point and elastic recovery tests, the incorporation of 11% and 16% w/w BCP in conventional CAP met the specifications of regulatory standards.

Bacterial cellulose produced from Gluconacetobacter xilinus was used to produce cellulose nanocrystals by sulfuric acid hydrolysis. Hydrolysis was performed with 64% sulfuric acid at 50 ºC with the hydrolysis time ranging between 5 and 90 min. The production of nanocrystals was observed to have size distributions that were dependent on hydrolysis times up to 10 min, after which time the suspensions showed distributions closer in size. Results from thermal analysis and X-ray diffraction showed that the amorphous cellulose was removed, leaving only the crystalline portion. Self-supported films were formed from the suspension of nanocrystals and had iridescence characteristics. The films were characterized by microscopy measures and specular reflectance.

In this work, the effects of incorporating cellulose nanocrystals from soy hulls (WSH30) on the mechanical, thermal, and barrier properties of methylcellulose (MC) nanocomposites were evaluated. MC/WSH30 nanocomposite films with different filler levels (2, 4, 6, 8, and 10%) were prepared by casting. Compared to neat MC film, improvements in the mechanical and barrier properties were observed, while thermal stability was retained. The improved mechanical properties of nanocomposites prepared may be attributed to mechanical percolation of WSH30, formation of a continuous network of WSH30 linked by hydrogen interactions and a close association between filler and matrix.

Methylcellulose was produced from the fibers of Mangifera indica L. Ubá mango seeds. MCD and MCI methylcellulose samples were made by heterogeneous methylation, using dimethyl sulfate and iodomethane as alkylating agents, respectively. The materials produced were characterized for their thermal properties (DSC and TGA), crystallinity (XRD) and Degree of Substitution (DS) in the chemical route. The cellulose derivatives were employed as mortar additive in order to improve mortar workability and adhesion to the substrate. These properties were evaluated by means of the consistency index (CI) and bond tensile strength (TS) tests. The methylcellulose (MCD and MCI) samples had CI increased by 27.75 and 71.54% and TS increased by 23.33 and 29.78%, respectively, in comparison to the reference sample. Therefore, the polymers can be used to produce adhesive mortars.