Search

Natural tannin-based foams are three-dimensional porous materials. Many different formulations have been investigated in order to reach foams with improved performance and increased commercial attractiveness. In this sense, each different tannin pH may impart different physical and thermochemical properties to the foams, which has not yet been fully elucidated. In the present study, seven rigid tannin foams (formaldehyde/sulfur-free) were produced using tannin extracts with variable pH values ( c.a. from 2.3 to 12.2). The most acidic tannin extracts (below 4.8) yielded tannin foams with the most lightweight (apparent density below 0.077 g.cm−3), homogeneous, and hydrophobic (water solubility below 23.5%) cellular-network architectures. Also, in most cases, the smaller the tannin pH, the higher the thermal stability of the foam. Further studies may address other technological requirements needed for thermal insulation applications.

Conhecer a durabilidade natural da madeira é importante na determinação dos locais de aplicação do material e na necessidade do uso de preservantes químicos. Por se tratar de espécies de rápido crescimento que podem atender as necessidades do mercado madeireiro, conhecer suas propriedades é relevante. O objetivo do presente trabalho foi determinar as propriedades mecânicas de três espécies de rápido crescimento submetidas a campo de apodrecimento. Para isso, 36 moirões (12 por espécie) de eucalipto, bracatinga e acácia-negra tiveram suas propriedades mecânicas em flexão estática determinadas em máquina universal de ensaios, antes e após exposição aos três diferentes ambientes de apodrecimento (campo aberto, floresta plantada e floresta nativa). De maneira geral, as madeiras apresentaram menor resistência mecânica quando expostas por maior período, consequência da degradação causada pelos fenômenos climáticos e por organismos xilófagos. Dentre as espécies estudadas, a Acácia-negra teve a maior resistência, ou seja, maior durabilidade natural, desempenhando valores maiores de MOE, MOR e TLP, do que o Eucalipto e a Bracatinga. No ambiente de campo aberto as madeiras apresentaram características mecânicas mais desejáveis do que nos locais de floresta nativa e plantada, decorrência dos fatores menos favoráveis ao desenvolvimento de organismos xilófagos. Dessa forma, a acácia-negra se destacou tanto em ambiente de campo como de floresta, podendo ser utilizada em situações que ocorre o seu contato com o solo. E, a exposição de madeiras em campo aberto é mais recomendada do que em locais de cobertura florestal.

Although wood is the main source for pulp and paper industry in Brazil, other renewable non-wood fibers could be key alternatives for papermaking. Thus, this study aimed to evaluate the properties of handsheets produced from a mixture of totora (Schoenoplectus californicus) (C.A. Mey.) and Eucalyptus spp. (eucalyptus) fibers. The pulps were refined in laboratory dybeater “PFI type,” varying the number of revolutions, in order to obtain refining curves in the range of 15° to 60° SR. The optical, physical, and mechanical properties of the papers produced were evaluated. The addition of totora fibers influenced refining process and paper properties. Moreover, the handsheets produced with the highest content of totora fibers showed low mechanical resistance. Totora is not suitable to be used as a single source of fibers, especially when good mechanical performance is required. However, when the fibers were mixed with eucalyptus, the mixture achieved reasonable resistance. Furthermore, higher opacity was obtained by the addition of totora (≥97%), which is interesting for the printing and writing segment.

Os fungos apodrecedores são agentes bióticos que, além da alteração de cor, causam deterioração e estão entre os maiores desvalorizadores de produtos à base de madeira. Nesse contexto, o trabalho teve como objetivo avaliar a perda de massa e a alteração da cor do cerne e do alburno da madeira de Maclura tinctoria (Tajuva), submetida a ensaio acelerado com os fungos Gloeophyllum trabeum (podridão parda) e Pycnoporus sanguineus (podridão branca). As amostras foram avaliadas quanto à resistência natural via análise da perda de massa após exposição a fungos apodrecedores. Com um colorímetro, através do sistema de medições Cielab, obteve-se as variáveis: luminosidade (L), coordenadas cromáticas (a* e b*), saturação (C), ângulo de tinta (h*) e calculado a variação total da cor (∆E*). O cerne de Maclura tinctoria apresentou elevada resistência aos fungos apodrecedores com perdas de massa de 1,52% para Pycnoporus sanguineus e de 0,96% para Gloeophyllum trabeum. O fungo Pycnoporus sanguineus deteriorou a madeira de alburno e cerne com maior intensidade e alterou a cor natural de branco-acinzentado/ amarelo para amarelo-claro. A variação total na cor da madeira foi considerável e com maior representatividade para o cerne.

The technological properties of wood are constituted by parameters, which after being analyzed, make it possible to define an appropriate use for this material. However, the deterioration of the wood due to the attack of termites, which find their food source in the chemical components, ends up altering these original technological characteristics, reducing their useful life and compromising their use. Thus, this study aimed to determine some technological properties of Pinus elliottii, as well as to evaluate the influence of deterioration caused by Nasutitermes termites in this wood. Specimens with dimensions of 20 x 20 x 150 mm (tangential x radial x longitudinal) were used as specimens. The physical properties evaluated were the basic density and linear shrinkage (tangential and radial contractions, and anisotropy coefficient), while the mechanical properties were represented through the Janka hardness test and compression parallel to the fibers. After 40 days of the biodeterioration test with Nasutitermes termites, changes in the equilibrium moisture content, retractability, water absorption rate and mechanical properties were evaluated. While the physical and mechanical properties evaluated showed values similar to those found in the literature, the deterioration caused by termites caused a reduction in hardness and parameters related to compression, increasing the dimensional instability of the wood, represented by the variation in the anisotropy coefficient. This made it possible to conclude that the biodeterioration resulting from the attack of termites directly affected the technological parameters of the wood, and consequently, its quality for the use in the purpose it could initially be destined.

Thermal treatments arise as an alternative to increase the physical and biological properties of wood, though they usually cause a reduction in mechanical strength. Therefore, the aim of th...

Aerogels are 3-D nanostructures of non-fluid colloidal interconnected porous networks consisting of loosely packed bonded particles that are expanded throughout their volume by gas and exhibit ultra-low density and high specific surface area. Cellulose-based aerogels can be obtained from hydrogels through a drying process, replacing the solvent (water) with air and keeping the pristine three-dimensional arrangement. In this work, hybrid cellulose-based aerogels were produced and their potential for use as dressings was assessed. Nanofibrilated cellulose (NFC) hydrogels were produced by a co-grinding process in a stone micronizer using a kraft cellulosic pulp and a phenolic extract from Maclura tinctoria (Tajuva) heartwood. NFC-based aerogels were produced by freeze followed by lyophilization, in a way that the Tajuva extract acted as a functionalizing agent. The obtained aerogels showed high porosity (ranging from 97% to 99%) and low density (ranging from 0.025 to 0.040 g·cm−3), as well a typical network and sheet-like structure with 100 to 300 μm pores, which yielded compressive strengths ranging from 60 to 340 kPa. The reached antibacterial and antioxidant activities, percentage of inhibitions and water uptakes suggest that the aerogels can be used as fluid absorbers. Additionally, the immobilization of the Tajuva extract indicates the potential for dentistry applications. The APC was funded by University of the Basque Country. CAPES (Coordination for the Improvement of Higher Education Personnel) for the doctoral scholarship of the first author.

Eucalyptus is one of the most fast-growing trees. Therefore, in the last decades it has been extensively planted and harvested so that nowadays Eucalyptus is one of the most popular trees of the planet. There are many genres of this plant and they are often treated as a large bunch of the same timber characterized by moderate mechanical and surface properties which hinder their usage for any sight application (e.g. flooring, cladding, ceiling). In this study four species of Eucalyptus: E. grandis, E. dunnii, E. cloeziana and E. tereticor-nis were undergone to densification through hydro-thermo-mechanical treatment (HTM) first and then to oil heat-treatment (OHT) in order to improve their mechanical properties and hydrophobicity. It was observed that low density species (E. grandis) reaches higher compression degrees while heavier species (E. tereticornis) reach densities over 800 kg/m³; however, HTM decrease the variability of the properties. Treatments at higher temperature (160 °C) involves higher compression degree, lower set-recovery and higher surface hydropho-bization, but also weaker mechanical properties. The hot oil post- treatment helps to contain the springback effect and to reduce the wettability of each specimen. Densified samples present similar surface hardness. The tailored application of the two treatments improves the properties of every Eucalyptus which can gain market also for nobler end-usages

Estudos que abordam os parâmetros tecnologicos da madeira de amplo uso, como Eucalyptus grandis, sao fundamentais, uma vez que seu uso e exploracao adequados dependem dessas caracteristicas. Atualmente, o implante dessa especie foi ampliado e o espacamento e um fator determinante. Portanto, o objetivo do presente estudo foi avaliar o espacamento das plantas e a variacao radial na flexao estatica da madeira de Eucalyptus grandis. Para a conducao do experimento, foram amostradas seis arvores para cada espacamento: 2,0 x 1,0 m, 3,0 x 1,0 e 0 x 1,5 m, totalizando 18 individuos aos sete anos de idade. Posteriormente, o primeiro registro de cada amostra foi seccionado em placas radiais e depois transformado em corpos de prova, identificados em intervalos regulares na direcao da casca da medula, com dimensoes de 2,5 x 2,5 x 41,0 cm, para realizar o teste de flexao estatica mecânica, seguindo as recomendacoes da ASTM D-143. Os resultados da resistencia mecânica mostraram uma variacao na direcao da casca da medula, onde os maiores valores de Modulo de Elasticidade (MOE), Modulo de Ruptura (MOR) e Tensao do Limite Proporcional (TPL) estavam proximos da casca. No entanto, o espacamento nao alterou o MOE, MOR e TLP do material submetido a flexao estatica. Assim, apenas a posicao radial influencia na qualidade da madeira. Os valores das propriedades mecânicas estudadas tiveram um aumento no sentido medula-casca, sendo mais acentuados na regiao proxima a casca. Palavras-chave: Propriedades tecnologicas; Propriedades mecânicas; Densidade populacional; Especies de crescimento rapido.

The present study aims to determine the moisture equilibrium of wood in the northern region of Rio Grande do Sul in different seasons, using data of relative humidity and temperature. Data were collected between the years 1990 and 2009, and were provided by EMBRAPA Trigo, Passo Fundo, Rio Grande do Sul. The estimate of the equilibrium moisture content was obtained through Simpson's equation (1971) using the theory of Hailwood and Horrobin. From this equation, the average equilibrium moisture content for each season (spring, summer, autumn and winter) was calculated, these seasons considered as treatments 1, 2, 3 and 4, respectively, and totaling 20 repetitions. Based on the results it was observed that the equilibrium moisture content varied over the seasons, with autumn having the highest average, equal to 15.6% and did not differ from winter, which has a moisture content of balance 15.5%. These levels, on the other hand, differ in relation to the spring and summer, corresponding to an equilibrium moisture content with average values of 14.1% and 14.7%, respectively.

O presente estudo teve como objetivo investigar a resistência ao intemperismo artificial de quatro revestimentos aplicados nas madeiras de duas espécies florestais. Para tal, foram utilizadas seis árvores de Eucalyptus grandis e três árvores de Tetrorchidium rubrivenium as quais foram desdobradas para confecção de 50 amostras para cada espécie, com dimensões de 5,0x7,0x1,0cm (largura, comprimento e espessura, respectivamente). A superfície das madeiras foi revestida com quatro acabamentos: polistein, verniz marítimo, tinta branca base óleo e tinta branca base água. As amostras sem revestimento e revestidas foram submetidas ao ensaio de envelhecimento acelerado durante 480 horas. A resistência ao intemperismo artificial foi avaliada por meio das modificações colorimétricas e morfológicas ao longo da exposição das madeiras e em função da molhabilidade superficial. Os principais resultados mostraram que a superfície das madeiras tendeu a tons opacos após exposição de 480 horas. Foi observado que os revestimentos não evitaram o aumento da molhabilidade superficial. Após todo o período de exposição, as madeiras não apresentaram modificações morfológicas tais como rachaduras e descascamento dos revestimentos, o que denota importante característica de proteção à madeira.Palavras-chave: Eucalyptus, canemaçu, modificação da superfície, envelhecimento acelerado, durabilidade da madeira. ARTIFICIAL WEATHERING OF FOUR COATINGS APPLIED ON WOODS OF TWO FOREST SPECIES ABSTRACT:The present study aimed to investigate the resistance to artificial weathering of four coatings applied on wood from two forest species. Six trees of Eucalyptus grandis and three trees of Tetrorchidium rubrivenium were cut to produce 50 wood samples for each species with dimensions of 5.0x7.0x1.0 cm (width, length and thickness, respectively). Wood surface was coated with four finishing products: polistein, marine varnish, oil-based white paint and water-based white paint. The uncoated and coated wood samples were subjected to accelerated aging test for 480h. The artificial weathering resistance was evaluated by color changes and surface wettability. The main results showed the coated woods tend to opaque tones after the exposure for 480h. The coatings did not avoid the increase of the surface wettability. After the exposure, both woods did not present morphological changes, such as cracks and peeling into the coatings, which represent relevant characteristics for wood protection.Keywords: Eucalyptus, canemaçu, surface modification, accelerated aging, wood durability. DOI

O presente trabalho tem o objetivo de descrever, microscopicamente, o lenho de Maytenus cassineformis Reissek, arvoreta nativa no Rio Grande do Sul. A descrição do lenho foi realizada com base nas normas da Associação Internacional de Anatomistas da Madeira (IAWA). Foram observados: vasos predominantemente solitários e em porosidade difusa; parênquima axial ausente; tecido radial heterogêneo; e fibras septadas e não-septadas. Os caracteres anatômicos são compatíveis com referências da literatura para Celastraceae, com pequenas divergências a nível de gênero.