Volta Redonda, Brazil
Volta Redonda, Brazil

Time filter

Source Type

Mulinari D.R.,UniFOA | Cruz T.G.,São Paulo State University | Cioffi M.O.H.,São Paulo State University | Voorwald H.J.C.,São Paulo State University | And 2 more authors.
Carbohydrate Research | Year: 2010

Surface modification of natural fibers has been made using different methods. In this paper, cellulose fibers from sugarcane bagasse were bleached and modified by zirconium oxychloride in situ. The chemically modified cellulose fibers were compared to those of bleached ones. Cellulose fibers were modified with ZrO2·nH2O nanoparticles through the use of zirconium oxychloride in acidic medium in the presence of cellulose fibers using urea as the precipitating agent. The spatial distribution characterization of hydrous zirconium oxide on cellulose fibers was carried out by combining both processing and image analyses obtained by SEM and statistical methodologies. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TG) were also used to characterize the nanocomposite. Results indicated that ZrO2·nH2O nanoparticles of about 30-80 nm diameter deposited on cellulose fibers were heterogeneously dispersed. © 2010 Elsevier Ltd. All rights reserved.


Pereira P.H.F.,São Paulo State University | Voorwald H.C.J.,São Paulo State University | Cioffi M.O.H.,São Paulo State University | Mulinari D.R.,UniFOA | And 2 more authors.
BioResources | Year: 2011

Cellulose fibers were isolated from sugarcane bagasse in three stages. Initially sugarcane bagasse was subjected to a pre-treatment process with hydrolyzed acid to eliminate hemicellulose. Whole cellulosic fibers thus obtained were then subjected to a two-stage delignification process and finally to a bleaching process. The chemical structure of the resulting cellulose fibers was studied by Fourier Transform Infrared (FTIR) spectroscopy. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the effects of hydrolysis, delignification, and bleaching on the structure of the fibers. Two different thermal analysis techniques were used to study the bleaching cellulose fibers. These techniques confirmed that cellulose fibers were isolated from sugarcane bagasse. A future goal is to use these fibers as reinforcement elements in composites, organic-inorganic hybrid, and membranes for nanofiltration.


Mulinari D.R.,UniFoa | Baptista C.A.R.P.,University of Sao Paulo | Souza J.V.C.,UniFoa | Voorwald H.J.C.,São Paulo State University
Procedia Engineering | Year: 2011

Actually, studies about the utilization of natural fibers as reinforcement in polymeric composites are increasing due to the improvements that fibers can provide to the product. In this work, chemical modification of the coconut fibers by alkaline treatment was studied in order to use them as reinforcement in polyester resin. Coconut fibers were modified during 1 hour with sodium hydroxide solution 1% wt/v. The modified fibers were evaluated by scanning electron microscopy, X-ray diffractometry, thermal analysis and Fourier Transform infrared spectroscopy. The composites were prepared by compression molding technique using 10% wt of fibers. The mechanical properties were evaluated by tensile and fatigue tests. The surfaces of the fractured specimens were examined in order to assess the fracture mechanisms. Results presented a decrease in fatigue life of composites when applied greater tension, due to bonding interfacial, which was not adequate. © 2011 Published by Elsevier Ltd.


Cerqueira E.F.,UniFoa | Baptista C.A.R.P.,University of Sao Paulo | Mulinari D.R.,UniFoa
Procedia Engineering | Year: 2011

Recently the interest in composite materials reinforced with natural fibers has considerably increased due to the new environmental legislation as well as consumer pressure that forced manufacturing industries to search substitutes for the conventional materials, e.g. glass fibers. This way, the objective of paper was evaluate the effect of chemical modification on mechanical properties of sugarcane bagasse fiber/PP composites. Fibers were pretreated with 10% sulfuric acid solution, followed by delignification with 1% sodium hydroxide solution. These fibers were mixed with the polypropylene in a thermokinetic mixer, and compositions with 5 to 20 wt% of fibers were obtained. The mechanical properties were evaluated by means of tensile, 3-point bending and impact tests. In addition, fracture analysis via SEM (secondary electrons mode) was performed. Results showed improve the tensile, flexural and impact strength of the composites in comparison to the polymer pure. © 2011 Published by Elsevier Ltd.


Dos Santos C.,UniFOA | Dos Santos C.,State University of Rio de Janeiro | Habibe A.F.,UFF EEIMVR | Rodrigues D.,University of Sao Paulo | And 3 more authors.
Materials Science Forum | Year: 2014

In this study, the effect of ball/powder ratios for grinding particles of a dental alloy consisting of 66%Co-28%Cr-6%Mo was investigated. Metal powders were obtained from SPEX mill, with tungsten carbide balls, setting the milling time to 60 minutes, 50% of volume of grinding vessel filled with powder and argon inert atmosphere. The ball/powder ratio was varied between 4:1, 6:1, 8:1, 10:1.The powders were characterized by XRD indicating Co as only crystalline phase present, which indicates that Cr and Mo enter into solid solution with the matrix Co. Measurement of crystallite size conducted using the Scherrer equation indicate the crystallite size about 10 to 6nm, due to the increase of the ball/powder ratio of 4:1 to 10:1. The morphology of the milled powders were analyzed by scanning electron microscopy (SEM) and indicate that the agglomerates created by the grinding process must have average sizes varying between 100μm and 200μm with the modification of the ball/powder. © (2014) Trans Tech Publications, Switzerland.


PubMed | Unifoa and University of Sao Paulo
Type: Journal Article | Journal: Revista do Colegio Brasileiro de Cirurgioes | Year: 2014

to evaluate the role of fibrillar extracellular matrix components in the pathogenesis of inguinal hernias.samples of the transverse fascia and of the anterior sheath of the rectus abdominis muscle were collected from 40 men aged between 20 and 60 years with type II and IIIA Nyhus inguinal hernia and from 10 fresh male cadavers (controls) without hernia in the same age range. The staining technique was immunohistochemistry for collagen I, collagen III and elastic fibers; quantification of fibrillar components was performed with an image analysis processing software.no statistically significant differences were found in the amount of elastic fibers, collagen I and collagen III, and the ratio of collagen I / III among patients with inguinal hernia when compared with subjects without hernia.the amount of fibrillar extracellular matrix components did not change in patients with and without inguinal hernia.


Melo-Silva C.L.,Federal University of Fluminense | Melo-Silva T.C.F.,Federal University of Fluminense | Carvalho C.F.,Federal University of Fluminense | Sudre J.P.S.,Federal University of Juiz de fora | And 3 more authors.
Materials Science Forum | Year: 2015

The aim of the study was to evaluate the difference in the surface of dental ceramics, the basis of lithium disilicate, varying the concentration and time of application of the acid. Samples of IPS e. max Press (Ivoclar) were divided into: G1-control; G2 hydrofluoric acid 10% - 20 sec; G3 hydrofluoric acid 10% - 40 sec; G4 hydrofluoric acid 5% - 20 sec G5 and hydrofluoric acid 5% - 40 sec. The samples were analyzed under SEM (Carl Zeiss) confocal microscope and (Carl Zeiss). The qualitative morphologic analysis showed that 40 seconds of conditioning promoted the dissolution of the vitreous component and the ceramic crystal display for the two concentrations. Hydrofluoric acid 10% showed higher values of roughness. One can conclude that conditioning for 40 seconds is more effective than the 20 seconds for the two concentrations hydrofluoric acid and 10% promoted a higher surface roughness in the ceramic. © (2015) Trans Tech Publications, Switzerland.


Martins G.A.,UniFOA | Pereira P.H.F.,São Paulo State University | Mulinari D.R.,UniFOA
BioResources | Year: 2013

Chemical modification of natural fibres has been carried out using different methods for such purposes as reinforcement in polymer matrices and heavy metals adsorption. In this work, palm fibres were modified by zirconium oxychloride in situ. The palm fibres that had been chemically modified were compared to those in nature using fibres that passed through 20 and 40 mesh screens to evaluate the influence of particle size on modification. Palm fibres were modified with ZrO2.nH2O nanoparticles through the use of zirconium oxychloride in an acidic medium in the presence of palm fibres using ammonium solution (1:3) as the precipitating agent. Scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectrophotometry (FTIR), and atomic emission spectrometry with inductively coupled plasma (ICP-AES) were used to characterize the hybrid materials. Results indicated that the particle size of the palm fibres influenced in the modification, because the fibres with smaller particle size had a greater deposition of inorganic material. The ICP technique revealed an increase of 21% nanoparticles ZrO2.nH2O deposited on fibres (40 mesh) when compared to fibres (20 mesh). The diameter of nanoparticles ZrO2.nH2O deposited on fibres was about 50 to 220 nm, as observed by SEM.


Souza P.S.,UniFoa | Rodrigues E.F.,UniFoa | Preta J.M.C.,UniFoa | Goulart S.A.S.,UniFoa | Mulinari D.R.,UniFoa
Procedia Engineering | Year: 2011

The use of natural fibers as reinforcement for thermoplastics has generated much interest due to the low cost, low density, high specific properties characteristics. In this work the mechanical properties of high density polyethylene/textile fibers residues composites were studied. Effect of pretreatment with sulfuric acid on textile fibers to prepare composites was made to provide an improvement in mechanical properties of these materials. This treatment on fibers was evaluated by X-ray diffraction technique. Composites were produced in a thermokinetic mixer in the following composition: 5 and 10 wt% fibers. After mixing the samples were injection molding according to ASTM D-638 specification. Specimens were tested in tensile mode and composite fractures surface were analyzed in a scanning electron microscopy. Also was studied moisture absorption. Results showed that HDPE/textile fibers residue presents good mechanical performance compared with high-density polyethylene. © 2011 Published by Elsevier Ltd.


Rodrigues E.F.,UniFoa | Maia T.F.,UniFoa | Mulinari D.R.,UniFoa
Procedia Engineering | Year: 2011

In the present work, chemical modification of the sugarcane bagasse fibers by estherification through anhydride system was studied to use as reinforcement in polyester matrix. Sugarcane bagasse fibers were estherified during 5 hours with acetic anhydride, toluene, acetic acid and percloric acid. The modification the fibers were evaluated by techniques scanning electron microscope (SEM) and X-ray diffractometry (XRD). Furthermore, fibers were mixed with the polyester resin and compression molding, in which fibers were responsible for 5 wt% in the composition. After that, the composite was left to cure at room temperature for 24 hours and machined into specimens of according to ASTM D-3039 specification. Tensile tests were carried out using EMIC machine according to ASTM D3039. Results relieved that composites presented better mechanical strength when compared to pure polymer, which exhibited an increase de 71.5% compared to the pure polymer. © 2011 Published by Elsevier Ltd.

Loading UniFOA collaborators
Loading UniFOA collaborators