Sandra M. Luz

Integrated processes for use of pulps and lignins obtained from sugarcane bagasse and straw: a review of recent efforts in Brazil.

Sugarcane bagasse and straw can be converted into pulps, oils, controlled-release formulations, chelating agents, and composites. This article reviews bagasse and straw conversion efforts in Brazil. Laboratory-scale processes were developed aiming at the integral use of these biomass byproducts. Organosolv pulping and oxidation of lignin are the most promising processes for the rational use of sugarcane residues. Fungal pretreatment and spectroscopic characterization are also discussed.

Integrated Processes for Use of Pulps and Lignins Obtained from Sugarcane Bagasse and Straw

Sugarcane bagasse and straw can be converted into pulps, oils, controlled-release formulations, chelating agents, and composites. This article reviews bagasse and straw conversion efforts in Brazil. Laboratory-scale processes were developed aiming at the integral use of these biomass byproducts. Organosolv pulping and oxidation of lignin are the most promising processes for the rational use of sugarcane residues. Fungal pretreatment and spectroscopic characterization are also discussed.

Surface Treatment of Coconut Fiber and its Application in Composite Materials for Reinforcement of Polypropylene

This work describes the surface treatment of coconut fiber and its application in composite materials for reinforcement of polypropylene. Before testing coconut fiber in composite materials, its susceptibility to chemical treatment was characterized by exposure to the following: (1) hot water; (2) aqueous NaOH 2% (w/v); and (3) a sequence of chemical treatments in hot water, extran 20% (v/v), acetone/water 1:1 (v/v), and aqueous NaOH 10% (w/v).The efficiency of each treatment was evaluated by Fourier transform infrared spectrometry analysis, indicating a reduction in the C=O peak. Besides that the scanning electron microscope revealed that treatment changed the morphology of the fibers. Thermogravimetric analysis showed that the insertion of fibers into PP caused a decrease in the thermal stability and differential scanning calorimetry exhibited that crystallization of PP was favored in the presence of fibers.

Composites from Brazilian natural fibers with polypropylene: mechanical and thermal properties

Brazil has a well established ethanol production program based on sugarcane. Sugarcane bagasse and straw are the main by-products that may be used as reinforcement in natural fiber composites. Current work evaluated the influence of fiber insertion within a polypropylene (PP) matrix by tensile, TGA and DSC measurements. Thus, the mechanical properties, weight loss, degradation, melting and crystallization temperatures, heat of melting and crystallization and percentage of crystallinity were attained. Fiber insertion in the matrix improved the tensile modulus and changed the thermal stability of composites (intermediary between neat fibers and PP). The incorporation of natural fibers in PP promoted also apparent T c and ΔH c increases. As a conclusion, the fibers added to polypropylene increased the nucleating ability, accelerating the crystallization process, improving the mechanical properties and consequently the fiber/matrix interaction.

Eco-composite: the effects of the jute fiber treatments on the mechanical and environmental performance of the composite materials

In this study, untreated and treated jute fiber composites were investigated as candidates to replace glass fibers as reinforcement to produce structural composites with better environmental performance. The surface of the jute fibers was modified by drying and bleaching/drying treatments to improve the wetting behavior of the apolar polyester, improving the mechanical properties of the composites. The mechanical characterization of the composites was obtained according to the ASTM standards (D-3039/D-790) and dynamic mechanical analysis. The environmental characterization was obtained by life-cycle assessment method. The treatment characterization was obtained by horizontal attenuated total reflectance infrared spectroscopy and thermogravimetry. Finally, jute composites were compared with glass composites and results show that the jute fiber treatments imply a significant increase of the mechanical properties of the composites without damaging their environmental performances.

Microestrutura e propriedades mecânicas de compósitos de polipropileno reforçado com celulose de bagaço e palha de cana

Composites utilizing vegetable fibers as reinforcement have demonstrated attracted increasing interest ofcrescent advantages from the scientific and industrial communities. Sugarcane bagasse and straw are renewable materials and when used as reinforcement in thermoplastic matrix can give origin to composite materials with low cost, low density and interesting mechanical properties. This work aimed to evaluate the mechanical and morphological properties of polypropylene composites reinforced with cellulose from sugarcane bagasse and straw. The cellulose was obtained through NaOH/AQ pulping process at 170oC for 3.5 h. The composites reinforced with 20 and 30 % wt of fibers were preparated utilizing a Dryser mixer. After ground and injection molding, these materials were analyzed by tensile and flexural tests, optical microscopy (OM) and scanning electron microscopy (SEM). The tensile strength of composites reinforced with fibers (20 wt.%) was similar to that of pure polypropylene, however, it decreased with the increase increasing amount of reinforcement. The tensile and flexural elasticity moduli increased up to 79.4 and 81.7 %, respectively, due to the high modulus of the fibers inserted inside the polymeric matrix. The composite surface analysis by OM showed homogeneous distribution of fibers inside the matrix and variable length and shape of the fibers. The cellulosic fibers from straw were also smaller than those from bagasse. SEM analysis of fractured composites exhibited pullout displacement of the fiber in with respect to thematrix and a typical behavior of brittle fracture. Cellulosic fibers obtained from sugarcane bagasse and straw resulted in composites with similar mechanical and morphological properties and provided rigidity to thematrix.

Environmental and technical feasibility of cellulose nanocrystal manufacturing from sugarcane bagasse

The environmental and technical feasibility of cellulose nanocrystal production from sugarcane bagasse fibers was evaluated. First, the life cycle assessment (LCA) is presented as a methodology to investigate the most feasible form of obtainment. The environmental impacts regarding climate change and water footprint were evaluated considering a gate-to-gate process and a functional unit of 1kg. The inventory data encompassed sugarcane plantation and pretreatment, bleaching and hydrolysis for bagasse generation. The twelve scenarios for extracting nanocrystals that were investigated consisted of treatment with sodium hydroxide or sodium chlorite followed by sulfuric acid hydrolysis. All products and processes were characterized by their yield and X-ray diffraction. As a result, all scenarios showed that the pretreatment stage was the most important contributor to the environmental impact. The comparison among the scenarios showed that nanocrystals produced by processes V - NaClO2/NaOH/H2SO4/30min/1x and IX - NaClO2/NaOH/HNO3/H2SO4/30min/1x presented low water consumption and minimal contributions to climate change. Therefore, considering the LCA, yield and crystallinity, the best processes were V and IX sequences. Finally, these cellulose nanocrystals were evaluated by their chemical composition, morphology and thermal stability, exhibiting hemicellulose and lignin removal, nanometric dimensions from 8 to 12nm, high crystallinity and low thermal stability.

Thermal and chemical characterization of sugarcane bagasse cellulose/lignin-reinforced composites

The aim of this work was to obtain and evaluate the thermal properties of castor oil polyurethane composites reinforced with lignin and cellulose from sugarcane bagasse. Sugarcane bagasse was pretreated and then delignified; then, the cellulose and lignin were milled. To produce the polyurethane, the mass ratio between polyol (castor oil) and diisocyanate was set to 1.5:1.0. The matrix was reinforced with a range of cellulose and lignin concentrations. The cellulose and lignin obtained by this process were chemically characterized. The composites were analyzed through SEM micrographs of fractured surfaces and thermal analysis. The presence of lignin or cellulose fibers in the polyurethane matrix decreases the thermal stability compared with the neat matrix.

Evaluation of Castor Oil Polyurethane Reinforced with Lignin and Cellulose from Sugarcane Straw

The search for materials from renewable sources such as vegetable oil-based polymers, polyurethane based on castor oil represents a promising alternative in researches. Using castor oil polyurethane as matrix for composites reinforced with lignin and cellulose from sugarcane straw is in tune with economical and environmental interests. The objective of this work was the evaluation of the changes on the structure and thermal behavior of castor oil polyurethane composites reinforced with lignin and cellulose from sugarcane straw. The cellulose and lignin were extracted from the straw by acid hydrolysis and then they were milled. For the production of the polyurethane, the mass reason between polyol (castor oil) and diisocyanate was 1.5:1.0. Reinforcement of the matrix was done changing the concentration of cellulose and lignin. SEM micrographs of fractured surfaces of the obtained composites and thermal analysis (TGA) were done. No lignin could be seen in SEM micrographs, what suggests a blend material behavior. The addition of cellulose fibers (30%) and lignin (40%) to the polyurethane matrix has caused an increase of the stiffness in the resulting composite when compared with the pure matrix. Above these rates, stiffness decreases. The presence of lignin or cellulose fibers in polyurethane matrix seems to increase mechanical properties of the composite, and also introduce better thermal stability than the pure matrix. Its presence might also bring other significant synergetic properties to the final composite, what has currently been studied. At the same time, the blend behavior of Polyurethane-Lignin composites has been investigated.

Thermal Properties of Polypropylene Composites Reinforced with Different Vegetable Fibers

Components based on composites reinforced with vegetable fibers have awaked interest in various industrial fields. The thermal properties of fibers, matrix and composite define the temperature limits for application and processing of these materials. In this work, a thermal analyzer TGA was used to evaluate the degradation and thermal events of vegetable fibers (abaca, curaua, fique, sisal, cellulose and in natura fibers from sugarcane bagasse and straw), polypropylene (PP) and PP composites reinforced with 15 wt% fibers. Samples were studied by using 30 to 600°C at 5°C.min-1 flow rate under helium or air atmosphere. TG curves from fibers showed weight loss in multiple stages. Before the thermal degradation peak, the abaca composite was more thermally stable, followed by fique, curaua and sisal composites. Thermal stability of composites was inferior for neat PP; however, it had a significant increase for the fiber.