Maria Alice Martins

Caracterização química e estrutural de fibra de sisal da variedade Agave sisalana

In recent years, the interest in the use of natural fibers in polymeric composite materials has increased significantly. In this work were investigated the structural, thermal, chemical, and physical properties of Brazilian sisal fiber from Agave sisalana variety. Our aim was to evaluate the quality and the performance of this fiber for industrial applications. Mechanical properties, chemical composition, X ray diffraction, and scanning electron microscopy (SEM) have been investigated with fibers along their length. The Brazilian sisal fibers studied have exhibited mechanical and thermal properties within the range reported in the literature and were suitable for use in polymeric composites.

Evaluation of reaction factors for deposition of silica (SiO2) nanoparticles on cellulose fibers

This study aimed to evaluate reaction conditions for deposition of SiO2 nanoparticles on the surface of cellulose fibers and their influence on moisture adsorption of the hybrid organic-inorganic material formed. SiO2 nanoparticle deposition was carried out with the sol-gel process testing four reaction times (2, 12, 18, and 24h) and three contents of the tetraethyl-orthosilicate (TEOS) precursor (1.9, 4.2 and 8.4g g(-1) of cellulose fiber). Modification time and TEOS content directly influence the amount of Si deposited on the fiber surface, nanoparticle diameter distribution, thermal stability, and resistance to moisture adsorption. There is a tendency of slight increase of nanoparticle size and the amount of Si deposited with increasing reaction time. SiO2 nanoparticles were bonded on the surface of the cellulose fibers and are able to improve thermal stability of the material, increasing onset degradation temperature. The moisture adsorption capacity of the modified cellulose fiber was reduced up to 50%.

Chemical treatment and characterization of soybean straw and soybean protein isolate/straw composite films

This work investigated changes in the chemical composition and structure of soybean straw (SS) treated with alkali (NaOH 5% and 17.5%) and bleached with hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl). Removal of the amorphous constituents increased the degree of crystallinity and the content of cellulose fibers particularly after reaction with high concentrations of alkali. Treatment with NaOH 17.5% contributed to the allomorph transition from cellulose I to II regardless of the bleaching agent, but H2O2 as bleaching agent promoted more effective delignification. This work also evaluated the potential use of treated and non-treated SS as reinforcement filler in soy protein isolate film (SPI). Films added with treated SS presented higher mechanical resistance, lower elongation at break, and lower solubility in water. Addition of non-treated SS did not affect the properties of the SPI film significantly. The low solubility and the reasonable water vapor permeability of the composite films make them suitable packaging materials for fresh fruit and vegetables.

Caracterização mecânica e térmica de compósitos de poli (cloreto de vinila) reforçados com fibras de sisal

Composites consisting of flexible polyvinyl chloride (PVC), plasticized with two different types of plasticizers and reinforced with sisal fibers, were processed on a two-roll mixing mill. Two plasticizers were used, a liquid plasticizer (polyester) and a permanent solid plasticizer (ethylene/ vinyl acetate/ carbon monoxide copolymer - Elvaloy ® ), to form two kinds of polymeric matrices. For each one of these matrices, the influence of plasticizers type, plasticizers content, size and quantity of sisal fibers in the composite properties has been studied. The fibers were washed with water at 80 °C during one hour. The composites with randomly distributed short fibers were characterized by mechanical analysis, scanning electron microscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). For each one of the polymeric matrices studied, the optimal size of sisal fiber was 6mm in order to have a better reinforcement, under the conditions investigated. The use of a solid plasticizer was feasible for PVC compositions and promoted a better fiber-matrix contact on the composites, increasing mechanical properties for plasticizer quantity over 40 phr, compared to the liquid plasticizer. Thermal analysis (TG and DSC) demonstrated that the replacement of the liquid by the solid plasticizer does not change the thermal behavior of the composites and unloaded polymeric matrices. For both matrices the elastic modulus is increased as the sisal fibers are added, when compared to unloaded matrices.

Biocomposite of cassava starch reinforced with cellulose pulp fibers modified with deposition of silica (SiO 2 ) nanoparticles

Eucalyptus pulp cellulose fibers were modified by the sol-gel process for SiO2 superficial deposition and used as reinforcement of thermoplastic starch (TPS). Cassava starch, glycerol, and water were added at the proportion of 60/26/14, respectively. For composites, 5% and 10% (by weight) of modified and unmodified pulp fibers were added before extrusion. The matrix and composites were submitted to thermal stability, tensile strength, moisture adsorption, and SEM analysis. Micrographs of the modified fibers revealed the presence of SiO2 nanoparticles on fiber surface. The addition of modified fibers improved tensile strength in 183% in relation to matrix, while moisture adsorption decreased 8.3%. Such improvements were even more effective with unmodified fibers addition. This result was mainly attributed to poor interaction between modified fibers and TPS matrix detected by SEM analysis.

Assessment of growth and yield performance of rubber tree clones of the IAC 500 series

The objective of this work was to evaluate the performance of 15 clones of the IAC 500 series of Hevea brasiliensis, developed at Instituto Agronomico (IAC), over a 12-year period, in the northwest region of Sao Paulo State, Brazil. The 15 new clones evaluated are primary clones obtained from selected ortets within half-sib progenies. The clone RRIM 600, of Malaysian origin, was used as the control. Dry rubber yield performance over a four-year period, mean girth at the tenth year, girth increment before and during tapping, thermal properties of the natural rubber produced and other characters of the laticiferous system were evaluated. Forty percent of the clones were superior in comparison to the control for yield. Clone IAC 500 recorded the highest yield (66.81 g per tree per tapping) over four years of tapping, followed by IAC 502 (62.37 g per tree per tapping), whereas the control recorded 48.71 g per tree per tapping. All selected clones were vigorous in growth. The natural rubber from this IAC clones showed thermal stability up to 300oC. No differences were observed in the thermal behavior of rubber among the IAC series and the RRIM 600 clones. The clones IAC 500, IAC 501, IAC 502, IAC 503 and IAC 506 are the more promising for small-scale plantations, due to growth and yield potential.

Using Commercial Enzymes to Produce Cellulose Nanofibers from Soybean Straw

This study used commercial enzymes to isolate cellulose nanofibrils (CN) and produce sugars from chemically pretreated soybean straw (SS) (stem, leaves, and pods) by alkali (NaOH 5 or 17.5% v/v at 90°C for 1źh or at 30°C for 15źh) and bleaching (NaClO2 3.3% or H2O2 4%) pretreatments. Depending on the pretreatment applied to the soybean straw, the yield of CN varied from 6.3 to 7.5źg of CN/100źg of SS regardless of the concentration of the alkaline solution (5 or 17.5%). The CN had diameter of 15źnm, measured over 300źnm in length, and had high electrical stability (zeta potentials ranged from ź20.8 to ź24.5). Given the XRD patterns, the crystallinity index (CrI) of CN ranged from 45 to 68%, depending on the chemical pretreatment the starting material was submitted to. CN obtained from SS treated with NaOH 17.5% and H2O2 (CrI = 45%) displayed better thermal stability probably because a lignin-cellulose complex emerged. The soluble fraction obtained in the first step of CN production contained a large amount of reducing sugars (11.2 to 30.4źg/100źg of SS). SS seems to be a new promising industrial source to produce CN via enzymatic-mechanical treatment, leading to large amounts of reducing sugars for use in bioenergy production.

Avaliação de clones de borracha natural crua por ensaios padrão e análise dinâmico-mecânica

Natural rubber (Hevea brasiliensis) from different clones (RRIM 600, IAN 873, GT 1, PB 235), a mixture made from these clones, and a commercial rubber, have been characterized by DMA, DSC, TGA, and standards methods (Wallace plasticity, PRI, Mooney viscosity, ash percentage, acetonic extract and nitrogen percentage). All the samples studied complied with standard specifications required for application in the rubber industry, and can be used in the rubber industry in blended or unblended forms. Among the clones, the best results of the standards methods were obtained from the RRIM 600 clone, and the blended form of the natural rubber increases its storage modulus.

Hydrophobic edible films made up of tomato cutin and pectin

Cutin is the biopolyester that protects the extracellular layer of terrestrial plants against dehydration and environmental stresses. In this work, cutin was extracted from tomato processing waste and cast into edible films having pectin as a binding agent. The influences of cutin/pectin ratio (50/50 and 25/75), film-forming suspension pH, and casting method on phase dispersion, water resistance and affinity, and thermal and mechanical properties of films were investigated. Dynamic light scattering and scanning electron microscopy revealed that cutin phase aggregation was reduced by simply increasing pH. The 50/50 films obtained by casting neutral-pH suspensions presented uniform cutin dispersion within the pectin matrix. Consequently, these films exhibited lower water uptake and solubility than their acidic counterparts. The cutin/pectin films developed here were shown to mimic tomato peel itself with respect to mechanical strength and thermal stability. Such behavior was found to be virtually independent of pH and casting method.

Characterization of açaí (E. oleracea) fruits and its processing residues

The aim of this work was to study the source of the acai residue for its possible commercial applications by characterizing the fruit (fresh and dry mass), and performing an anatomic study of the pericarp from which were identified the origin of the anthocyanins, and fatty acids, and fibers; also the vascular system, its fibers constituents and fibrils were characterized. It was concluded that anthocyanins were located on the epiderm and external parenchyma, and that solids retained on the sieve come from the sclerenchyma, and that the fatty acids come from the storage parenchyma. The vascular tissue was formed by the fibers around 20 mm length. The length distribution of the fibrils had a mean length of 580µm.