Aplicação de indentação instrumentada na caracterização mecânica de poliuretana derivada de óleo de mamona

Abstract

Resumo: Neste trabalho são investigadas as propriedades mecânicas de poliuretana derivada do óleo de mamona, utilizando a técnica de indentação instrumentada com penetradores de geometrias piramidal e esférica. Foi analisada a influência da forma do penetrador utilizado nos ensaios de indentação instrumentada para se obter valores das propriedades mecânicas de polímero derivado de óleo de mamona. Os penetradores utilizados são de pontas piramidais dos tipos Berkovich e canto de cubo e esférico de raio igual a 150 μm em um Nanoindenter XP TM com cargas aplicadas entre 1 e 200 mN. As penetrações variam de acordo com o formato do penetrador, sendo maiores para pontas agudas. A dureza e o módulo de elasticidade foram determinados, utilizando o método de Oliver e Pharr. Verificou-se que os valores medidos para a dureza são maiores para penetradores mais agudos. Os valores obtidos com a ponta piramidal Berkovich foram de 0,14 GPa para pequenas penetrações e 0,12 GPa para maiores penetrações. Já os valores obtidos com ponta canto de cubo foram 25 a 30% maiores. Isso está relacionado com os volumes das regiões que apresentam deformações plásticas elevadas, no caso de penetradores agudos comparados com os volumes das regiões que sofrem deformações viscoelásticas. A viscosidade aparente determinada, utilizando penetrador esférico em testes de força aplicada constante, é igual a (22 ± 2) × 10 12 Pa.s. Palavras-chave: Poliuretana, viscoelasticidade, indentação instrumentada, dureza, módulo de elasticidade. Instrumented Indentation Applied to The Mechanical Characterization of Polyurethane Derived From Castor OilAbstract: The mechanical properties of polyurethane derived from castor oil, obtained by instrumented indentation technique with pyramidal and spherical indenters are reported. The influence of the indenter shape on the values of mechanical properties of the polymer was investigated. The indentations were made with pyramidal Berkovich, cube corner and a spherical indenter with radius of 150 μm in a Nanoindenter XP TM . The applied loads varied between 1 and 200 mN. The penetration depth increases for acute indenters, being higher for the cube corner tip. The hardness and elastic modulus were determined using the method of Oliver and Pharr. It was found that the measured values for hardness are higher for more acute indenters. The hardness with the pyramidal Berkovich tip was 0.14 GPa for small penetrations and 0.12 GPa for higher penetration depths. The values obtained with a cube corner tip were 25 to 30% higher. This is related to the volumes of regions with high plastic deformation in the case of acute indenters compared to the volumes of regions that present viscoelastic deformation. The apparent viscosity determined using the spherical indenter, in tests with applied constant forces, is equal to (22 ± 2) × 10 12 Pa.s.

Polyurethane derived from castor oil reinforced with long cotton fibers: Static and dynamic testing of a novel eco-friendly composite material

“…Azevedo et al. 53 carried out the characterization of polyurethane derived from castor oil, one of the tests being the thermogravimetry test, finding two steps in the degradation process of polyurethane. The first one is from 300 ℃ to 400 ℃ with 65% of mass loss, which refers to the disruption of urethane bonds, while the second step is from 400 ℃ to 500 ℃ with 30% of mass loss, which refers to the decomposition of the ester linkages present in the polyol.…”

“…Then two more peaks are given at temperatures 410.72 C and 463.28 C. The second peak of the curve is found when there is 37.86% of the mass present in the composite, and the third peak is 27.12% of the mass present in the composite. Azevedo et al 53 carried out the characterization of polyurethane derived from da Costa et al…”

The influence of fiber size on the behavior of the araucaria pine nut shell/PU composite

“…Two distinct events can be observed for the PU, the first one occurring between 250°C and 350°C with a mass loss of 40%. In this temperature range, the urethane bonds are broken [25] . The second event takes place between 350°C and 500°C with a mass loss of 60%, and this is attributed to the decomposition of the ester bonds present in polyol [26] .…”

Flow-injection spectrophotometric determination of captopril in pharmaceutical formulations using a new solid-phase reactor containing AgSCN immobilized in a polyurethane resin

“…Another feature of the growing market demand is the use of polyols derived from vegetable oils (e.g. castor oil), a renewable source, and the simplicity of synthesis of derivatives, such as that used in the present study (Azevedo et al, 2009).…”