Gamma and ultraviolet radiation effects on hardness, elastic modulus and viscoelastic properties of polyurethane derived from castor oil (PU) were investigated by nanoindentation tests. Modifications on surface morphology, induced by radiation, were observed by atomic force microscopy. The polyurethane derivate from castor oil shows good resistance to gamma radiation, with only small changes in hardness, elastic modulus, viscoelastic properties and contact angle. The hardness of PU increases at the near surface region due to UVA radiation and decreases after UVC radiation. The contact angle for water drop decreases after UVC radiation, but not after gamma radiation, despite a significant increase in roughness. Such results are attributed to different responses from polyurethane to radiation energy. Increase in hardness due to UVA is attributed to a higher crosslinking at shallow depths, while a decrease in mechanical properties may be attributed to chain scission. These results are consistent with the modifications on viscoelastic properties. Shore D hardness did not show the same trend as observed by nanoindentation results. Hardness, viscoelastic properties and contact angle of castor oil polyurethane are more severely influenced by UVC radiation, while gamma radiation does not have a significant effect.

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.

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.

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.

Estudos termogravimétricos e calorimétricos exploratórios diferenciais de hexametilenoditiocarbamatos de níquel(II), cobre(II), zinco(II) e cádmio(II) foram realizados sob atmosferas dinâmicas de ar e nitrogênio, para avaliar as etapas e os produtos de decomposição térmica. Esses produtos, quando cristalinos, foram caracterizados por difratometria de raios X, sendo predominantemente constituídos por sulfetos e óxidos metálicos sob N2 e ar, respectivamente. Usando espectrofotometria na região do ultravioleta, também foram determinados o pKa = 3,6 ± 0,2 para o ácido hexametilenoditiocarbâmico em força iônica igual a 0,50 mol dm-3 (KCl) a 25,0 °C e os parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 2,21 x 10-2 s-1 e t½ lim = 156 s).

Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of nickel(II), copper(II), zinc(II) and cadmium(II) hexamethylenedithiocarbamates were performed under nitrogen and air atmospheres in order to investigate the steps and products of thermal decomposition. When obtained in a crystalline form, the decomposition products were identified by their X-ray diffraction patterns. Metal sulfides and oxides were the major residues under nitrogen and air atmospheres, respectively. Spectrophotometric measurements in the ultraviolet region were used to estimate the pKa = 3.6 ± 0.2 for the haxamethylenedithiocarbamic acid at 0.50 mol dm-3 ionic strength (KCl) at 25.0 °C and the kinetic parameters of decomposition at different pH values (k lim = 2.21 x 10-2 s-1 and t½ lim = 156 s).

The aim of this research is to study the biodegradation of a polyurethane derived from castor oil, which contains polyester segment in its molecular structure, thus becoming susceptible to the microorganisms attack. The biodegradation of polyurethane was tested in contact with microorganisms resulting from microbiological grease degrading agents, in appropriate liquid media, with a duration of 156 days. The study was done by using scanning electron microscopy (SEM), thermogravimetry (TG) and Fourier-transform infrared spectroscopy with accessory for attenuated total reflectance (FTIR-ATR). The results suggest that the degradation of polyurethane derived from castor oil occurs. TG curves are used in order to indicate the biodegradation, showing changes between the thermal behavior of the samples that were inoculated with microorganisms and control. In the FTIR-ATR spectra, there are detectable changes between the spectra of control and attacked specimens; this suggests that degradation occurs, with the decreased intensity of the absorption band at 1042 cm-1, corresponding to the esters links.

Estudos termogravimétricos e calorimétricos diferenciais de morfolinoditiocarbamatos de NH4+, Mn2+, Co2+, Ni2+ e Cu2+ 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 (NaClO4) à 25,0 °C e parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 0,14 ± 0,04 s-1 e t½ lim = 5,3 ± 1,2 s).

Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of NH4+, Mn2+, Co2+, Ni2+ e Cu2+ 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 (NaClO4) at 25.0 °C and kinetic parameters of decomposition at different pH values (k lim = 0.14 ± 0.04 s-1 e t½ lim = 5.3 ± 1.2 s).

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.

Estudos termogravimétricos e calorimétricos diferenciais para ditiocarbamatos de NH4+, Na+, Zn2+, Cd2+ e Pb2+, derivados de aminas cíclicas contendo nitrogênio como heteroátomos, foram realizados em atmosferas de ar e nitrogênio, para avaliar a influência da tensão angular dos anéis na decomposição térmica destes compostos, em relação à formação de tiocianatos metálicos como via de decomposição. Os intemediários formados foram caracterizados por difração de raios-X, tendo sido encontrados oxissulfatos de Zn2+, Cd2+ e Pb2+, sob atmosfera de ar, o que sugere a decomposição térmica nestas condições como via sintética para estes compostos. Os produtos de decomposição final obtidos foram sulfetos metálicos sob nitrogênio e óxidos dos metais de transição e sulfato de sódio sob ar. Entalpias de fusão são também descritas, com base nos resultados de DSC.

Thermogravimetric and Differential Scanning Calorimetric investigation of the thermal behaviour of NH4+, Na+, Zn2+, Cd2+ e Pb2+ dithiocarbamates obtained from cyclic amines, is described under nitrogen and air atmospheres in order to investigate the effect of a cyclic ring on the mechanism of decomposition. Intermediates were identified by X-ray Diffraction analysis. Zn2+, Cd2+ e Pb2+ oxysulphates were detected under air atmosphere suggesting the thermal decomposition under these conditions as an alternating synthetic route to prepare those compounds. The final decomposition products were the metallic sulphides under N2 atmosphere while transition metal oxides and sodium sulphate were obtained under air. Melting enthalpies are also reported from DSC data.

Neste trabalho apresenta-se um método espectrofotométrico, baseado em equipamentos com arranjo linear de diodos ("diode array"), para determinação de pKa dos ácidos ditiocarbâmicos derivados da pirrolidina (HPyr-I) e da piperidina (HPip-II). A elevada velocidade de leitura do equipamento, torna possível minimizar o problema da decomposição dos ditiocarbamatos, em meio ácido. Os valores de pKa obtidos foram 3.10(I) e 3.51(II), em I = 0.50 mol L-1 (NaClO4) à 25.0 °C, sendo consistentes com os mecanismos de decomposição ácida. Apresenta-se também uma discussão baseada na forma dos espectros obtidos em meio ácido e básico e sua relação com a ordem dos valores de pKa, a qual é inversa em relação a valores determinados anteriormente.

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.