Castor-oil biobased foam: the effect of the composition on the physical and mechanical properties via a statistical mixture design.

PU foams are versatile materials that find applications in a wide range of products, from upholstery to packaging and construction. These foams consist primarily of two components, polyol and prepolymer, and their concentrations play a crucial role in determining their physical and mechanical properties. A second-order mixture design approach is used in this work to identify the significant components and their contributions on the physical-mechanical properties of biodegradable castor oil-based foams. The experimental design includes three components: two types of polyols and one prepolymer. These components are varied in nine distinct conditions to evaluate their effects on properties such as expansion rate, bulk density, compressive strength, and tensile strength. The Scheffé's quadratic model coefficients exhibit R-squared values higher than 0.84 in most cases. Chemical analysis using infrared spectroscopy confirms the successful formation of the urethane bond during the manufacturing process. The biobased foams developed in this work have densities ranging between 61 and 100 kg m-3, compressive modulus of 11-15 MPa and compressive strength between 273 and 429 kPa. The tensile modulus varies between 3.2 and 4.9 MPa, with a tensile strength in the range of 370-500 kPa. These results highlight the potential of biodegradable castor oil-based foams as promising alternative materials to traditional synthetic foams.

Residual Mechanical Properties and Durability of High-Strength Concrete with Polypropylene Fibers in High Temperatures.

Investigations into the fire resistance of high-strength concrete (HSC) is extremely important to optimize structural design in construction engineering. This work describes the influence of polypropylene fibers on the mechanical properties and durability of HSC at high temperatures (25, 100, 200, 400, 600 and 800 °C). HSC specimens with 2 kg/m3 composed of polypropylene fibers are tested in a temperature range of 25 to 800 °C, followed by microstructural analysis. In addition, a statistical analysis is designed to identify the effect of factors, namely temperature and polypropylene fibers, and their interactions on mechanical properties and water absorption, electrical resistivity, mass loss and ultrasonic velocity. Most of the properties are improved by the incorporation of fibers, obtaining highly predictable regression models. However, the polypropylene fibers reduce compressive strength but improve the residual mechanical properties up to 400 °C.

Painéis de partículas de madeira leucena e resina poliuretana derivada de óleo de mamona / Particleboard manufactured with leucena wood and polyurethane resin castor oil based

O presente trabalho objetivou avaliar as características físico mecânicas de chapas aglomeradas com partículas de leucena (Leucaena leucocephala) e resina poliuretana derivada de óleo de mamona, sendo investigados o módulo de resistência à flexão (MOR), adesão interna (AI), densidade aparente (d ap) e teor de umidade (u m). Os experimentos foram desenvolvidos com base nos procedimentos metodológicos da norma brasileira ABNT NBR 14810:2002. As chapas foram confeccionadas com pressão de compactação de 4MPa, temperatura de 90°C, partículas com 5% de teor de umidade e adição de 10% de resina poliuretana monocomponente e bicomponente derivadas de óleo de mamona. Os resultados obtidos demonstraram que as densidades aparentes obtidas foram superiores às recomendadas pela norma brasileira, sendo os painéis confeccionados com resina bicomponente 22,67% superiores ao limite superior estabelecido pela normatização técnica brasileira. Os painéis confeccionados com resina poliuretana monocomponente apresentaram os maiores valores para o teor de umidade. O módulo de resistência à flexão dos painéis fabricados com resina bicomponente mostrou ser 43,7% superior ao valor definido pela norma. A adesão interna dos painéis fabricados com resina monocomponente foi 2,5 vezes superior ao valor estipulado pela norma. Do intervalo de confiança entre médias para as resinas mono e bicomponente, apenas a adesão interna e densidade apresentaram equivalência estatística. Os coeficientes de determinação obtidos das regressões entre a adesão interna e densidade para ambas as resinas validaram o modelo de ajuste linear, sendo possível estimar a adesão interna com o conhecimento da densidade aparente das chapas.

This research aimed to test particleboard with leucena (Leucaena leucocephala) wood particles and polyurethane resin castor oil based. The response variables are: modulus of rupture (MOR), internal adhesion (AI), apparent density (d ap) and wood moisture content (u m). The experiments were developed based on the methodological procedures of the ABNT NBR 14810:2002 standard. The particleboards were manufactured by hot-pressing at 4MPa and 90°C, using timber particles with 5% of moisture content and 10% of monocomponent and bicomponent polyurethane resin. The higher moisture content was achieved when the monocomponent polyurethane resin was used. The bicomponent polyurethane resin provided a percent increase of 43.7% and 22.7% on the modulus of rupture and apparent density, respectively, when compared to the standard limit. The internal adhesion of the panels manufactured with monocomponent resin was 2.45 times higher than the standard limit. The confidence interval between means revealed that the internal adhesion and apparent density exhibited statistical equivalence. A good correlation between the internal adhesion and apparent density was found, for this reason it was possible to estimate the internal adhesion of the panels based on the apparent density data.

Metodologia para o cálculo dos módulos de elasticidade longitudinal e transversal em vigas de madeira de dimensões estruturais / Methodology used to determine the shear and longitudinal modulus of elasticity in timber beams

Este trabalhou objetiva apresentar uma metodologia analítica para o cálculo dos módulos de elasticidade longitudinal (E) e transversal (G) em vigas de madeira de dimensões estruturais, segundo o emprego das teorias de vigas de Euler Bernoulli e Timoshenko, sendo utilizado o ensaio de flexão estática a três pontos. As madeiras testadas foram o Pinus elliottii e a Corymbia citriodora. Os resultados encontrados relevaram ser o módulo de elasticidade longitudinal 18,70 vezes superior ao módulo transversal do Pinus elliottii e 21,2 superior ao módulo transversal do Corymbia citriodora, sendo estes compatíveis quando comparada a relação entre E e G estabelecida pela norma Brasileira ABNT NBR 7190:1997 (Projeto de Estruturas de Madeira), que define ser o módulo de elasticidade longitudinal vinte vezes superior ao transversal.

This paper proposed a test method to obtain the shear (G) and longitudinal (E) modulus of elasticity in timber beams with structural dimensions, based on the static three-points bending tests and the Euler Bernoulli and Timoshenko beams theories. The woods tested were the Corymbia citriodora and Pinus elliottii. The results revealed that the longitudinal modulus of elasticity of Pinus elliottii is 18.70 greater than the shear modulus, and 21.16 greater than the shear modulus of Corymbia citriodora, being consistent this results when compared to the proposed by the Brazilian standard ABNT NBR 7190:1997 (Design of Wood Structures), being the longitudinal modulus of elasticity twenty times greater than the shear modulus.