Instrumented indentation applied to the mechanical characterization of polyurethane derived from castor oil

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.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.CNPqFAPES

Biodegradation of polyurethane derived from castor oil

The aim of this research was to study the biodegradation of a polymer derived from castor oil, which is a renewable, natural material that is a practical alternative for the replacement of traditional polyurethane foams. Due to its molecular structure, which contains polyester segments derived from vegetable oil, the polymeric surface is susceptible to microorganism attack. This study tested the biological degrading agent that was in contact with the microorganisms resulting from microbiological grease degrading agents, when foam was inoculated. Solid-media agar-plate tests were conducted for their potential to evaluate the biodegradation of polymeric particles by specific strains of microorganisms during 216 hours. The growth rate was defined. This technique provides a way of distinguishing the degradation abilities of microorganisms from the degradability of materials

The spectrophotometric determination of the pka of pyrrolidinedithiocarbamic and piperidinedithiocarbamic acids, based on diode array measurements

A spectrophotometric method, based on the use of a diode array spectrophotometer, is proposed in order to determine the pKa of pyrrolidinedithiocarbamic (HPyr-I) and piperidinodithiocarbamic (HPip-II) acids. The high speed of data acquisition of the equipment made it possible to minimize the problem of acid decomposition. The values obtained were 3.10(I) and 3.51(II) in I = 0.50 mol L-1 (NaClO4) at 25.0 °C, and are consistent with the acid decomposition mechanism. A discussion is presented based on the shape of the compound spectra in acidic and basic media and their relation to the order of the pKa values for I and II

Determination of toxic aluminum for wheat roots by potentiometry with fluorid ion selective electrode

Avaliou-se o método potenciométrico com o eletrodo seletivo de fluoreto (ESIF) para estimar as espécies tóxicas de Al às raízes do trigo em soluções pura e de solo e em solos ácidos tratados com doses de calcário. Comparou-se Al-ESIF com o método espectrofotométrico com a solução de ferron. O crescimento das raízes diminuiu exponencialmente com o aumento de Al-ESIF, cuja técnica detectou principalmente as espécies A13+, Al(OH)2+ e Al(OH)2+. A concentração de Al-ESIF nos solos sem calcário (pH 4,0) variou de 30 a 2100 x 10-6M e diminuiu com o aumento do pH até valores não detectáveis em pH > 5,6. Al-ferron foi superior ao Al-ESIF em todos os pH estudados. Os complexos de A1 em pH > 5,6 foram reativos com ferron, mas não com F-. -Al-ESIF apresentou a melhor estimativa das espécies tóxicas de Al às raízes do trigo.A potentiometric technique with fluoride ion selective electrode (FISE) was evaluated for its ability to estimate toxic Al species for wheat root growth in pure and soil solution, and in limed and unlimed treatments of selected acid soils. Al-FISE was compared with a spectrophotometric-ferron method. Root growth decreased exponentially with increasing Al-FISE. The dominant forms of Al-ESIF was estimated by Geochem as A13+, AlOH2+, and Al(OH)2+. Al--FISE concentration in unlimed soil solution ranged from 30 to 2100 x 10-6M and decreased with increasing soil pH. Al-ferron was greater than Al-FISE for all pH studied. Above pH 5.6 Al-FISE was undetectable but Al-ferron increased in soils high in dissolved organic carbon. Al complexes above pH 5.6 was reactive with ferron but not with F- ion. Al-FISE was better predictor of the toxic Al species for wheat root growth than Al-ferron

Projektaktivitäten des Aachener Competence Center-Elektronic Commerce

The study of Aloysia gratissima essential oil from leaves was obtained by hydrodistillation using a Clevenger type apparatus. The essential oil composition was analyzed by GC and GC/MS. The major compounds were identified representing 94.7% of the oil. The most abundant compounds were isopinocamphone (cis-3-pinanone) (25.4%), limonene (15.1%), and guaiol (12.7%).Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Estudo voltamétrico do complexo de cobre(II) com o ligante vermelho de alizarina S, adsorvido na superfície do eletrodo de grafite pirolítico Voltammetric study of complex of copper (II) with alizarin red S ligand, absorbed on surface of pyrolytic graphite electrode

<abstract language="eng">The alizarin red S (ARS) has been used as a spectrophotometric reagent of several metals for a long time. Now this alizarin has been used as modifier agent of electrodes, for voltammetric analyses. In this work cyclic voltammetry experiments was accomplished on closed circuit, with the objective of studying the voltammetric behavior of alizarin red S adsorbed and of its copper complex, on the surface of the pyrolytic graphite electrode. These studies showed that ARS strongly adsorbs on the surface of this electrode. This adsorption was used to immobilize ions copper(II) from the solution

Solution and solid state thermal stability of morpholine dithiocarbamates

Estudos termogravimétricos e calorimétricos diferenciais de morfolinoditiocarbamatos de NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ foram realizados em atmosferas de ar e nitrogênio, para avaliar a influência da presença do oxigênio como heteroátomo no anel da amina na decomposição térmica. Produtos de decomposicão térmica foram caracterizados através de difratogramas de raios X, sendo predominantemente formados por sulfetos metálicos, sob atmosfera dinâmica de nitrogênio e óxidos metálicos, sob ar. Usando espectrofotometria, também foram determinados o pKa = 3,56 para o ácido morfolinoditiocarbâmico em força iônica 0,50 mol dm -3 (NaClO 4 ) à 25,0 °C e parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 0,14 ± 0,04 s -1 e t ½ lim = 5,3 ± 1,2 s). Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ morpholinedithiocarbamates were performed under nitrogen and air atmospheres in order to investigate the effect, in the thermal decomposition, of the presence of an oxygen as the heteroatom in the amine ring. Decomposition products were identified by their X-ray diffraction patterns. Metal sulfites and oxides were the major residues under nitrogen and air atmospheres, respectively. Spectrophotometric measurements were used to estimate the pKa =3.56 for the morpholinedithiocarbamic acid at 0.50 mol dm -3 ionic strength (NaClO 4 ) at 25.0 °C and kinetic parameters of decomposition at different pH values (k lim = 0.14 ± 0.04 s -1 e t ½ lim = 5.3 ± 1.2 s)

Avaliação radiográfica da cobertura acetabular à cabeça femoral, após osteotomia tripla e aplicação de cunha sacroilíaca, em pelve de cadáveres de cães

Na tentativa de evitar algumas das dificuldades associadas à osteotomia pélvica tripla (OPT), foi desenvolvido experimentalmente o método de aplicação de cunha na junção sacroilíaca para aumentar a ventroversão acetabular. O objetivo deste estudo foi aplicar as técnicas de cunha sacroilíaca e OPT em cadáveres e avaliar radiograficamente a eficácia da ventroversão acetabular. Para tal, foram utilizados 10 cadáveres de cães, adultos, com 15-25 kg. em cada hemipelve direita foi realizada OPT com placas de 20° e 40°. Na hemipelve esquerda foram aplicadas cunhas nas articulações sacroilíacas de 20° e 40°. Avaliações radiográficas em projeções ventrodorsais foram realizadas para mensuração da cobertura acetabular à cabeça femoral nas duas técnicas. de acordo com os dados obtidos pode-se observar que não houve diferença entre a técnica de OPT e o uso de cunha sacroilíaca utilizando implantes de 20° e 40°, mas ocorreu diferença significativa (p<0,05) entre os cães antes e após a aplicação dos implantes de 20° e 40°, e também entre os que receberam implantes de 20° e os de 40°. A aplicação de cunha sacroilíaca produziu resultados semelhantes à OPT, e também se mostrou como de mais fácil aplicação.Attempting to avoid difficulties associated to triple pelvic osteotomy (TPO), the sacroiliac wedge method was experimentally developed to increase the acetabular ventroversion. The goal of this study was to apply the techniques of sacroiliac wedge and TPO to canine cadavers and radiographically evaluate the efficacy of acetabular ventroversion. Ten cadavers of adult dogs weighting 15-25 kg were used. To each right hemipelvis the technique of TPO with 20° and 40° plates was applied. In the left hemipelvis, 20° and 40º wedges in the sacroiliac joint were applied. Radiographic evaluations in standard projections were carried out for measurement of the acetabular covering of the head of the femur in the two techniques. There was no significant differences between TPO and the use of sacroiliac wedge using implants of 20° and 40°, however a significant difference (p<0,05) could be observed before and after application of the 20° and 40° implants, as well as between those that received 20° and of 40° implants. The application of sacroiliac wedge produced similar results of those observed in TPO, and it is more feasible.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP