13 research outputs found
Caracterização anatômica da fibra de bambu (Bambusa vulgaris) visando sua utilização em compósitos poliméricos.
O desenvolvimento de materiais compósitos utilizando fibras vegetais como reforço é crescente e vêm conquistando novos segmentos de mercado, pois as fibras vegetais apresentam baixo custo, biodegradabilidade, menor densidade e boas propriedades mecânicas, físicas e térmicas adequadas às aplicações industriais. Este trabalho apresenta os resultados de recentes pesquisas sobre a fibra de Bambusa vulgaris realizadas no laboratório de anatomia da madeira da Universidade Federal de Lavras, onde foram avaliadas suas dimensões e relações entre elas, bem como o ângulo de micro fibrila. O principal objetivo deste estudo é mostrar que estes materiais não convencionais podem apresentar propriedades semelhantes e/ou superiores a outros materiais que tradicionalmente vem sendo empregados na produção de compósitos. Os resultados da pesquisa mostraram que os valores de ângulo de micro fibrila (11,54º), comprimento (2.299,47 μm), diâmetro da fibra (13,93 μm), diâmetro do lume (3,81 μm), relação comprimento/largura (172,53) e espessura da parede celular (5,06 μm) poderão maximizar as propriedades mecânicas dos compósitos onde forem utilizadas tornando-os mais resistentes e mais leves em comparação com outras fibras.The development of composite materials using vegetable fibers as reinforcement is increasing and comes conquering new market segments, because the vegetable fibers have low cost, biodegradability, lower density and good mechanical properties, physical and thermal suitable to industrial applications. This paper presents the results of recent research about the fiber of Bambusa vulgaris performed in the laboratory of wood anatomy of the Federal University of Lavras, where were evaluated their dimensions and relations between them, as well as the micro fibril angle. The main objective of this study is to show that these unconventional materials may have similar properties and/or superior to other materials that traditionally come being employed in the production of composite materials. The results of the research has shown that the values of angle of micro fibril angle (11.54º), length (2,299.47 μm), fiber diameter (13.93 μm), lumen diameter (3.81 μm), length/width ratio (172.53) and cell wall thickness (5.06 μm) will be able to maximize the mechanical properties of composites where they will be used becoming then stronger and lighter compared with other fibers
Pulpa de bambú tratada con NaOH y dianhídrido benzofenona tetracarboxílico como refuerzo de nuevos materiales poliméricos.
Bamboo admittedly and engineering material widely used for buildings in several countries. However, lack of good interfacial adhesion, low melting point, and poor resistance towards moisture make the use of natural fiber reinforced composites less attractive. The aim of this work was esterify the refined pulp of bamboo came from kraft industrial pulping, previously treated with sodium hydroxid and organic solvents for the production of less hydrophilic materials. In order to verify the occurrence of reaction, assays of spectroscopy in the region of IV, thermogravimetry, elementary analysis and water absorption were performed. After the reaction, the infrared spectra presented bands related to the ester and carboxylic acid groups, evidencing the exchange of OH groups for ester groups. This test also shows a decrease in the absorbance ratio due to the presence of ester group causing a reduction in the crystallinity index of the sample. These results were proven by the gain in the value of carbon content after the elementary analysis. In the water absorption test, the pulp modified with dianhydride showed the lowest level as compared to other samples. The thermogravimetric analysis also showed a decrease in initial temperature of pulp degradation, as well as decrease in the moisture, facts that proved the efficiency in the modification using dianhidrido BTDA.El objetivo de este trabajo fue esterificar pulpa refinada procedente de bambú industrial kraft, pre-tratados con hidróxido de sodio y disolventes orgánicos para producir materiales menos hidrofílicos. Con el fin de verificar la aparición de reacción de esterificación, espectroscopia infrarroja, análisis termogravimétrica, análisis elemental y absorción de agua fueron realizadas. Después de la reacción, el espectro infrarrojo mostró bandas relacionadas con los grupos éster y grupos de ácido carboxílico, que muestra el intercambio de grupos OH por grupos éster. Esta pruebla también mostró una proporción reducida de la absorbancia debido a la presencia del grupo éster causando una reducción en el índice de cristalinidad de la muestra. Estos resultados se corroboraron por un aumento en la cantidad
de contenido de carbono después del análisis elemental. En la prueba de absorción de agua, la pulpa modificada con dianhídrido mostro el nivel más bajo en comparación con otras muestras. El análisis termogravimétrica mostró también una reducción en la temperatura de inicio de la degradación de pulpa refinada, así como una disminución en el contenido de humedad, los eventos que demostraron La eficacia de la modificación utilizando BTDA dianhídrido
Dimensional stability of Bambusa vulgaris for the production of GLB and furniture.
The objective of this study was to determine
the dimensional stability of Bambusa vulgaris, analyzing
the technical viability of its use by industries of GLB
(glued laminated bamboo) and furniture. The variations
occurred in the dimensions of the specimens after immersion
in water and dried on a stove were investigated. The
assessment of quality was performed through the anisotropy
of shrinkage and swelling, volumetric shrinkage and
swelling, basic density and water absorption of 2-year-old
samples made in the form of slivers. The bamboo presented
lower values of shrinkage and swelling anisotropy for the
basal region. The mean total value of volumetric shrinkage
for the studied regions was stable, and was therefore
classified as medium shrinkage. Because the mean values
of basic density were lower than 0.5 g/cm3 in all the
regions, the species was classified as a light material. The
present study also showed that the increase of basic density
was related to a decrease on the rates of water absorption.
These results point to the great potential use of such species
on the sector of GLB and furniture
Dynamic mechanical behavior of vinylester matrix composites reinforced by Luffa cylindrica modified fibers.
Currently, there is a demand for new engineering
materials presenting a combination of strength, low
density, processing easiness, and reduced costs. In this context,
polymer matrix composites reinforced by natural fibers
have been studied in recent years due to their ecological and
economic advantages. Some fibers are still little explored in
literature despite presenting a great potential as reinforcement
like Luffa cylindrica. The present work aims at the preparation
and characterization of a vinylester thermoset matrix
composite material reinforced by fibers of the natural
L. cylindrica fruit after modification treatments. In this study,
extraction treatments in organic solvents, mercerization, and
a quite new esterification with BTDA dianhydrides were
used and the results showed that in all cases, the composite
materials reinforced by Luffa fibers have showed improvements
in mechanical and thermal properties compared to
the vinylester matrix. As an example, 50% tensile increase
was obtained for the composite reinforced by fibers esterified
with benzophenone tetracarboxylic dianhydride when
compared with thermoset matrix
Quantification of moisture contents in iron and manganese ores.
The moisture contents of several synthetic and natural goethite-bearing samples were determined by
the loss-of-mass method and by the Karl-Fischer titration. It was found that drying at 105°C did not
remove all the water from these samples, and that temperatures above 200°C would be required to completely
remove the adsorbed water. The multiple peaks observed in the TGA and DSC measurements are
not due to the dehydroxylation of goethite, but are due to the release of adsorbed water. The decomposition
of goethite into hematite occurs with the release of adsorbed water from room temperature up to
the onset of the main dehydroxylation peak. The dehydroxylation occurs in a broad range of temperatures
due to the existence of a particle-size distribution, surface hydroxyls and formation of a hematite coating.
The determination of all adsorbed water is best performed by adding the powdered sample into the Karl-
Fischer reaction vessel
Polymorphic screen and drug–excipient compatibility studies of the antichagasic benznidazole.
The purpose of this study was to investigate the
polymorphism and compatibility of benznidazole (BNZ), a
drug used in the treatment of Chagas disease. This drug
was subjected to a polymorphic screen using a number of
solvents and precipitation procedures to explore the possible
existence of different crystal structures of BNZ. The
compatibility of BNZ with selected pharmaceutical excipients
was evaluated in binary mixtures, in a ratio of 1:1
(w/w). These results were then analyzed with a variety of
techniques, including differential scanning calorimetry,
Fourier transform infrared spectroscopy, and X-ray powder
diffractometry. No polymorphic forms of BNZ were
detected despite some observed changes in the DSC profile.
The thermal data indicate interaction of the drug with excipients
hydroxyethylcellulose, polyethylene glycol, and
hydroxypropyl-b-cyclodextrin. Additional studies using
infrared spectroscopy confirm the incompatibility of BNZ
with only the polyethylene glycol. This excipient should
not be used in the development of solid dosage forms
containing BNZ
Influence of Moringa oleifera derivates in blends of PBAT/PLA with LDPE
Abstract There are few studies about Moringa oleifera derivates in polymer developments where vegetable oil was used as a plasticizer and a biodegrading agent. The polymerization of moringa oil (MO) was carried out assisted by microwaves without catalysts presence. There aren’t studies about the polymerization of MO using microwaves technology. Moringa’s oil and its polymer (PMO) were used as a biodegrading agent for mixtures of low density polyethylene (LDPE) with poly(butylene adipate-co-terephthalate)/poly(lactic acid) (PBAT/PLA). The mixtures producted films that were characterized and submitted to biodegradation analysis in order to discuss the influence of moringa components. Results showed that both moringa components improved thermal properties and reduced the crystalline phase of the mixture. The addition of PMO had improved the biodegradation capacity up to five times while MO had improved it up to three times. The results showed the greatest influence of moringa components on biodegradation of mixtures with cited polymers