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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 the study was to determine the brittleness of Eucalyptus wood submitted to freezing and heat treatments. Freezing occurred with green condition specimens and the heat treatment with samples in equilibrium moisture content (20°C and 65% RH). The static bending test was carried out on an EMIC® universal testing machine. The freezing showed slight changes in the mechanical properties of Eucalyptus wood, not differing from natural wood. The treatments with high temperatures caused significant losses in mechanical strength, evidenced by decreases in maximum load and increases in brittleness. In the combined treatments, there was no sum of effects. Therefore, heat treatments modify the mechanical properties of wood, increasing its brittleness and following the tendency that, as the temperature increases, the mechanical resistance decreases.

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:

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.

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.