Lourival Marin Mendes

Utilização de eucaliptos e de madeiras nativas no armazenamento da aguardente de cana-de-açúcar

The aim of this work was to evaluate different species of Eucalyptus and of native wood to make barrels for storage of sugar cane spirit. It was studied the chemical, anatomical and physical properties of the woods and made physical-chemical analyses of the sugar cane spirit storage during twelve months. The barrels made with wood of Eucalyptus presented little permeabilidade to liquids and a low dimensional estability, provoking discard of great part of them. The chemical composition of the different Eucalyptus wood showed constant polissacarydes and lignina contents but differing among extractives levels, that were higher than the oak wood. The composition of the sugar cane spirit stored in these kind of wood showed pattern according to the Brazilian law, indicating their potential use as barrels for the storage of sugar cane spirit. The native wood, also showed low dimensional instability with no leaking, constant polyssacarydes and lignina contents and higher extractive levels than oak wood. The sugar cane spirit composition after storage was also according to the law.

ANÁLISE TERMOGRAVIMÉTRICA EM CLONES DE EUCALIPTO COMO SUBSÍDIO PARA A PRODUÇÃO DE CARVÃO VEGETAL

No Brasil, o uso da madeira, para geracao de energia, tem sido relacionado a producao de carvao, em decorrencia da demanda existente pelo produto junto ao setor siderurgico e, em sua grande maioria, sao especies do genero Eucalyptus. No entanto, em funcao das variacoes que ocorrem na qualidade da madeira do referido genero, faz-se necessario estuda-las, pois esse fato pode ocasionar consequencias negativas na qualidade e rendimento do carvao vegetal, as quais refletirao nas operacoes dos alto-fornos siderurgicos. O objetivo do presente trabalho foi estudar a qualidade da madeira de diferentes materiais geneticos de eucalipto para producao de carvao vegetal por meio da analise termogravimetrica. No estudo, considerou-se a resistencia a degradacao termica da madeira e as caracteristicas qualitativas e quantitativas do carvao. Pelos resultados, verificou-se que os maiores picos de degradacao termica ocorreram na faixa de temperatura compreendida entre 300 e 400oC; o material genetico um foi o que apresentou a menor perda de massa total e o tres foi o menos estavel, tendo esses apresentado, respectivamente, maior e menor rendimento gravimetrico em carvao vegetal; todos os materiais geneticos apresentaram, de modo satisfatorio, rendimento gravimetrico em carvao vegetal e qualidade dos mesmos.

How the chemical nature of Brazilian hardwoods affects nanofibrillation of cellulose fibers and film optical quality

A wide range of alternative cellulose fibers for the development of new green nanomaterials can be obtained from Brazil’s natural resources. The objective of the work is to evaluate the influence of the chemical composition of hardwoods on the nanofibrillation process and optical quality of nanofiber films. Wood wastes were selected from three native Amazonian species and from exotic planted Eucalyptus grandis species. Wood sawdust was submitted to chemical alkali and bleaching pretreatments. Nanofibers were produced from the bleached fibers after 10, 20, 30 and 40 passes through a Super Mass Colloider grinder, and films were produced by the casting method. Raw sawdust, alkali-treated fibers and bleached fibers were evaluated by the major chemical components, syringyl/guaiacyl ratio, Fourier transformed infrared spectroscopy, oxygen/carbon ratio and scanning electron microscopy. Morphological characteristics of nanofibers and films were analyzed by transmission and scanning electron microscopies. Optical parameters studied for the films were the opacity, total color difference and b value. The main challenge to delignification was attributed to the low syringyl/guaiacyl ratio. The different chemical natures of Amazonian and eucalyptus hardwoods greatly affected pretreatments and, consequently, the nanofibrillation and optical quality of the films. Consequences observed for highly purified cellulose starting fibers are: (1) lower diameters for individual nanofiber elements; (2) fewer opaque and colored films produced from nanofibers; (3) a tendency to stabilization of the nanofibrillation process after 20 passes through the grinder. For species whose chemical nature hindered cellulose purification, the increased number of passes through the grinder continuously decreased the opacity.

Efeito da incorporação de casca de café nas propriedades físico-mecânicas de painéis aglomerados de Eucalyptus urophylla S.T. Blake

The objective of this study was to evaluate the influence of the incorporation of Coffee husks in the production of particleboard with Eucalyptus urophylla S.T. Blake. The panels were produced incorporating 25%, 50%, and 75% of Coffee husks at three levels of resin phenol-formaldehyde (6, 9 and 12%) and 1% of paraffin. The nominal density of the panels was 0.7 g/cm3 and the cycle of pressing consisted in a pressure of 3.92 MPa under a temperature of 180°C for 8 minutes. By the results it was possible to observe that the physical properties of the particleboard have a linear relationship decreasing with the increase in the level of resin, and increasing with the increase in the percentage of coffee husks, showing higher values of water absorption and thickness swelling. The mechanical properties show a linear relationship growing with the increase of resin level, and decreasing with a reduction the percentage of coffee husk association. The way that the search was conducted, the incorporation of the Coffee husks harms the quality of the panels produced.

MICRO/NANOFIBRILAS CELULÓSICAS DE EUCALYPTUS EM FIBROCIMENTOS EXTRUDADOS

Uma forma alternativa para producao de fibrocimento e a extrusao, que permite entre muitas vantagens a producao de compositos cimenticios com geometrias diferenciadas e requer baixo investimento inicial para producao industrial. Nesse contexto,o objetivo desse trabalho foi obter micro/nanofibrilas celulosicas de Eucalyptus e avaliar o efeito da adicao de diferentes conteudos dessas micro/nanofibrilas nas propriedades fisico-mecânicas de fibrocimentos envelhecidos naturalmente e em ambiente climatizado. Micro/nanofibrilas celulosicas produzidas em desfibrilador mecânico foram caracterizadas quanto a sua morfologia. Compositos extrudados produzidos com 0,5% e 1,0% (em massa) de micro/nanofibrilas foram comparados com compositos sem micro/nanofibrilas. Compositos produzidos a partir das tres formulacoes foram submetidos aoenvelhecimento natural e em ambiente controlado para posterior caracterizacao por flexao estatica, vibracao flexural e propriedades fisicas. Nao houve diferenca significativa no modulo de ruptura (MOE), limite de proporcionalidade (LOP), e deformacao especifica total entre os compositos com reforco de 0,5 e 1,0% de micro/nanofibrilas e aqueles sem reforco. O modulo elastico estatico (MOE) aumentou, e a energia especifica diminuiu com 1,0% de micro/nanofibrilas. O modulo de elasticidade dinâmico (E) dos compositos aumentou com o incremento do conteudo de micro/nanofibrilas (1,0%) e do tempo de exposicao ao envelhecimento natural e controlado. O presente estudo indica que as propriedades fisicas (absorcao de agua - AA, porosidade aparente - PA e densidade aparente - DA) e mecânicas de fibrocimentos sao sensiveis a formulacao e que esse comportamento varia em funcao do tempo (135 dias). Essas informacoes devem ser consideradas uteis para o desenvolvimento de novos materiais reforcados com micro/nanofibrilas de celulose.

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.

Use of maize cob for production of particleboard

Os residuos agricolas sao materiais gerados em grande quantidade no Brasil, podendo se acumular no ambiente, gerando graves problemas. Um desses residuos que merecem destaque e o sabugo de milho. Uma das alternativas para o reaproveitamento do sabugo seria a producao de paineis aglomerados em mistura com madeira. Objetivou-se, neste trabalho, avaliar a viabilidade da utilizacao do sabugo de milho para a producao de paineis aglomerados. As porcentagens de sabugo de milho utilizadas foram de 0%, 25%, 50%, 75% e 100% associadas com particulas de madeira de Pinus oocarpa. Os paineis foram produzidos com 8% de ureia-formaldeido e 1% de parafina (base massa seca de particulas). Na prensagem dos paineis, foi utilizada pressao de 3,92 MPa e temperatura de 160o C por um periodo de 8 minutos. O aumento da substituicao da madeira de pinus pelo residuo sabugo de milho promoveu melhoras significativas para as propriedades de absorcao de agua, apos duas horas e inchamento em espessura, apos duas e vinte e quatro horas. As propriedades mecânicas apresentam relacao decrescente com a porcentagem de incorporacao de sabugo de milho.

Efeito da associação de bagaço de cana, do tipo e do teor de adesivo na produção de painéis aglomerados.

Este trabalho teve como objetivo avaliar o efeito da associacao de bagaco de cana, tipo e teor de adesivo nas propriedades fisico-mecânicas de paineis aglomerados com madeira de pinus spp. O delineamento experimental se constituiu de um esquema fatorial 3x2x3, sendo tres porcentagens de substituicao de madeira de pinus por bagaco de cana - 25, 50 e 75%; dois tipos de adesivos - fenol-formaldeido (FF) e ureia-formaldeido (UF); e tres teores de adesivo - 6, 9 e 12%. O ciclo de prensagem utilizado foi de pressao de 40 kgf/cm2, temperatura de 160°C para UF e de 180°C para FF, e por um tempo de 8 minutos. Mediante os resultados pode-se concluir que: 1) Para a porcentagem de associacao de bagaco de cana, nas propriedades em que foi observado efeito significativo, a tendencia foi de diminuicao da qualidade dos paineis a medida que se aumenta a quantidade de associacao de bagaco de cana; 2) O adesivo UF se mostrou estatisticamente igual ou superior a FF em todas as propriedades avaliadas; 3) Os teores de adesivo apresentaram efeito significativo para todas as propriedades analisadas, sendo que, com excecao da propriedade ligacao interna, em todas as outras propriedades o teor de 12% foi estatisticamente superior a 6%, e ainda igual ou superior a 9%.

Clones de Eucalyptus versus a produção de polpa celulósica.

The wood quality is defined by combining several intrinsic characteristics of the tree to its use. This research aimed to evaluate some of the wood characteristics of Eucalyptus clones and its performance in kraft pulping. Fifteen clones, 5.8 years-old were used, two trees from each clone, totaling thirty trees. The evaluated wood characteristics were: basic density, fiber dimensions (fiber length, wall thickness, lumen diameter) and chemical composition (cellulose, lignin, hemicelluloses, extractives and ash contents). Four samples were cooked at the laboratory for each tree, using different active alkali, to establish the delignification curve. These alkali loads were selected after exploratory cooking to obtain an eighteen kappa number at the medium point of the curve. In the cooking were appraised the screened, the pulp viscosity and consumed alkali. The yield results varied from 43.4 to 52.0%, the active alkali from 17.5 to 23.4%, the consumed alkali from 15.5 to 20.0% and the pulp viscosity from 19.9 to 61.4 cP.

Rationalizing the impact of aging on fiber–matrix interface and stability of cement-based composites submitted to carbonation at early ages

The objective of this work is to show the effect of carbonation at early stages on fiber–cement composites and impact on hydration, chemical and dimension stability. Carbonation increased the content of CaCO3 polymorphs and consumed Ca(OH)2 and other hydrated calcium phases. Micrographs and energy-dispersive spectrometry showed the CaCO3 formed is precipitated in the pore structure of the matrix, decreasing diffusion of Si, S, and Al during hydration. Therefore, a refining process of pore sizes is produced, and fiber–matrix interface in carbonated composites was improved, leading to volume stabilization of the composite, as indicated by lower drying shrinkage and lower porosity.