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Polímeros, Volume: 28, Número: 3, Publicado: 2018
  • Surface treated bagasse fiber ash on rheological, mechanical properties of PLA/BFA biocomposites Original Article

    Sitticharoen, Watcharin; Uthiyoung, Chet; Passadee, Nateechai; Wongprom, Chanokpol

    Resumo em Inglês:

    Abstract The use of silica based bagasse fiber ash (BFA) as a reinforcing filler in polylactic acid (PLA) biocomposites was examined. The effects of surface-treated BFA on the rheological, swelling behavior, and mechanical properties and water absorption of biocomposites were studied. BFA was treated using a silane coupling agent (Bis-[3-(triethoxysilyl)-propy]-tetrasulfide). Composites with BFA were varied from 5 to 25wt.%. The PLA/BFA composite melts were pseudoplastic non -Newtonion fluid and exhibited a shear thinning behavior. The viscosity of the surface-treated BFA biocomposites was higher than that of the untreated. The viscosity of the composites decreased with increasing BFA content and shear rate. The extrudate swell of the composites increased with increasing shear rate, whereas it decreased with increasing BFA content and die temperature. The extrudate swell tended to be suppressed when surface-treated BFA was used. Silane treated BFA composites showed improvement in their mechanical properties, and exhibited significantly reduced water absorption.
  • Water-uptake properties of a fish protein-based superabsorbent hydrogel chemically modified with ethanol Original Article

    Martins, Vilásia Guimarães; Costa, Jorge Alberto Vieira; Prentice, Carlos

    Resumo em Inglês:

    Abstract Hydrophilic polymers can form hydrogels, which are able to absorb and retain as much water as one hundred times their weight. Polymers based on natural products have been drawing attention since they are biocompatible, biodegradable and nontoxic. The aims of this study were to produce and to characterize a biopolymer with superabsorbent properties from fish protein isolates. Hydrogels were produced from protein isolates from Whitemouth croaker processing wastes chemically modified. The extension of change in lysine residues, kinetics in water-uptake capacity, pH effect, ionic strength over the absorption of water by hydrogels and the behavior of the biopolymer when subject to successive hydration and dehydrations were investigated. Results showed that acid modified protein without ethanol treatment reached a maximum absorption of 103.25 gwater/gdry gel, while the same sample modified with ethanol reached 216.05 gwater/gdry gel.
  • Characterization of additives in NR formulations by TLC-IR (UATR) Original Article

    Murakami, Lidia Mattos Silva; Azevedo, Joyce Baracho; Diniz, Milton Faria; Silva, Leandro Mattos; Dutra, Rita de Cássia Lazzarini

    Resumo em Inglês:

    Abstract It is a well-established fact that rubber accelerator is essential to provide solution in different sectors. However, there is a reversal process which can reduce the material performance. Sulfur accelerators donors and organic peroxides have been presented as a solution to the problem. The methodology development that can separate or characterize those components is a challenge and still allows gaps, explained by the application of conventional technique to reach this goal. This study aimed at contributing to the use of off-line coupling of thin layer chromatography (TLC)/infrared spectroscopy (IR) by Universal Attenuated Total Reflection (UATR) for analysis of N-cyclohexyl-2-benzotiazolsulfenamide (CBS), tetraethylthiuram disulfide (TMTD) and dicumyl peroxide (DCP), in natural poly-cis-isoprene (NR) formulations, containing naphthenic oil. The best results were obtained for the plasticizer and DCP, in formulations that had a greater proportion of these compounds. The separation of CBS and TMTD was made with less effectiveness, due to bands overlapping.
  • Effect of disinfection techniques on physical-mechanical properties of a microwave-activated acrylic resin Original Article

    Fortes, Carmen Beatriz Borges; Collares, Fabrício Mezzomo; Leitune, Vicente Castelo Branco; Schiroky, Priscila Raquel; Rodrigues, Stéfani Becker; Samuel, Susana Maria Werner; Petzhold, Cesar Liberato; Stefani, Valter

    Resumo em Inglês:

    Abstract The effects of disinfection by microwave irradiation and immersion in peracetic acid on the physical-mechanical properties of a microwave-activated acrylic resin were evaluated. Specimens of acrylic resin were divided into a control group (specimens not disinfected) and 2 test groups subjected to one disinfection method: microwave irradiation at 850 W for 1 minute or immersion in 50 mL of 0.2% peracetic acid for 5 minutes. Specimens were submitted to Knoop hardness, flexural strength, flexural modulus, Izod impact, water sorption and solubility, glass transition temperature, and degree of conversion tests. Microwave disinfection significantly increased the mean Knoop hardness, Izod impact strength, water sorption, water solubility and glass transition temperature, whereas the flexural properties remained unaffected. Microwave disinfection increased the degree of conversion. Peracetic acid disinfection showed no changes in any properties. Both disinfection techniques did not adversely affect the evaluated properties.
  • Synthesis of poly(ethyl methacrylate-co-methyl methacrylate) obtained via ATRP using ruthenium benzylidene complexes Original Article

    Afonso, Maria Beatriz Alves; Gonçalves, Lucas Gomes; Silva, Talita Teixeira; Sá, José Luiz Silva; Batista, Nouga Cardoso; Goi, Beatriz Eleutério; Carvalho Júnior, Valdemiro Pereira

    Resumo em Inglês:

    Abstract Atom-Transfer Radical Copolymerization (ATRP) of methyl methacrylate (MMA) and ethyl methacrylate (EMA) under different reaction conditions was conducted using Grubbs 1st ( 1) and 2nd (2) generation catalysts. Initially, the study focused on the reactivity of the catalysts in ATRP of EMA individually, then the syntheses of poly(MMA-co-EMA) were also conducted in different mixtures of monomers ([MMA]/[EMA] = 100/200 and [MMA]/[EMA] = 200/100). Conversion and semilogarithmic kinetic plots as a function of time were related to the different catalysts and reaction conditions. The values of Mn and PDI also changed when different catalysts were used in the presence of Al(OiPr)3, and more controlled polymerizations were achieved using 1. In the syntheses of poly(MMA)-co -(EMA), conversion of 60% was reached for both catalysts at different [MMA]/[EMA] ratios for 16 h; however, for shorter time, 4 h, better conversion values were obtained using 1 as catalyst for both [MMA]/[EMA] = 100/200 or 200/100.
  • Polystyrene and cornstarch anti-corrosive coatings on steel Original Article

    Souza, Cinthia de; Teixeira, Ricardo Luiz Perez; Lacerda, José Carlos de; Ferreira, Carla Regina; Teixeira, Cynthia Helena Bouças Soares; Signoretti, Valdir Tesch

    Resumo em Inglês:

    Abstract This work aims to evaluate the performance of anticorrosive thermoplastic coatings in cold rolled steel sheets. Two types of thermoplastic coatings were studied: polystyrene (PS) and cornstarch. These types of coatings are applied for protection against corrosion during transport and storage of steel plates after cold rolling until delivery to stamping or other processing. The good performance for these coatings is suitably standardized to ABNT NBR 5915-2: 2013 and ASTM A1008 / A1008M-2016. According to corrosion tests carried out in saline chamber, the coatings were satisfactory in different degrees of guarantee of corrosion protection on ASTM 1080 steel, in accordance with standards mentioned.
  • Chitosan and gum arabic nanoparticles for heavy metal adsorption Original Article

    Abreu, Flavia Oliveira Monteiro da Silva; Silva, Nilvan Alves da; Sipauba, Mateus de Sousa; Pires, Tamara Fernandes Marques; Bomfim, Tatiana Araújo; Monteiro Junior, Oyrton Azevedo de Castro; Forte, Maria Madalena de Camargo

    Resumo em Inglês:

    Abstract Chitosan (CT) is a polysaccharide with the ability to adsorb metals on its surface. In this work, CT-based nanoparticles (NPs) are produced by complex formation with gum arabic (GA) to increase their adsorbent potential for removal of heavy metals in aqueous medium. Adsorption efficiency is evaluated as a function of NP composition and polysaccharide concentration. NPs are sized from 250 to 375 nm at a zeta potential up to -25 mV, suggesting stability to adsorb metals. In particular, CTGA56 and CTGA80 NPs adsorbed a substantially higher amount of copper ions than pure CT. Adsorption kinetics studies showed that the reaction process followed a pseudo second-order model and the adsorption isotherm results fit a Langmuir model, highlighting the monolayer adsorption process with prominent adsorption capacity. These findings indicate the adsorbent potential of CTGA NPs and suggest that these particles can be used for removal of metal ions from contaminated water sources.
  • UATR and NIRA evaluation in the quantification of ATBC in NC blends Original Article

    Mello, Talita de Souza Dias; Diniz, Milton Faria; Dutra, Rita de Cássia Lazzarini

    Resumo em Inglês:

    Abstract The paint industry requires rapid and accurate methodologies of raw materials qualitiy controls. For example, the evaluation of the suitable ratio of binary mixtures of polymer/plasticizer such as nitrocellulose (NC)/acetyl tributyl citrate (ATBC) must be done, since this ratio is directly related to the performance of the final product. However, there is a small number of quantitative methodologies of such control in the literature. In this context, in this paper, the applicability of Infrared Fourier Transform Spectroscopy (FT-IR) techniques by using universal total attenuated reflection (UATR), in the middle infrared (MIR), and the reflectance analysis in the near infrared region (NIRA) is evaluated for the quantification of plasticizer ATBC in mixtures with NC. MIR and NIR methodologies presented good results such as: practicality of not requiring refined sample preparation, analysis time about 30 min and good accuracy, suitable data for using in the quality control laboratories of paint industry.
  • Polyurethane derived from Ricinus Communis as graft for bone defect treatments Original Article

    Sousa, Tatiana Peixoto Telles de; Costa, Maria Silvana Totti da; Guilherme, Renata; Orcini, Wilson; Holgado, Leandro de Andrade; Silveira, Elcia Maria Varize; Tavano, Orivaldo; Magdalena, Aroldo Geraldo; Catanzaro-Guimarães, Sérgio Augusto; Kinoshita, Angela

    Resumo em Inglês:

    Abstract This work evaluated polyurethane (Polyquil®) as a graft for treatment of bone defects. Bone defects of 1.5 × 0.5 cm were made in the calvaria of 16 rabbits. Eight animals had their defects treated with Polyurethane (Treated) and 8 of them had their defects filled with blood clot (Control). In the second experiment, segmental defects of 0.5 cm were performed at the zygomatic arch of 16 rabbits. Eight animals were treated by guided bone regeneration, using a latex membrane, associated to grafting of polyurethane while the others were not treated (Control). The bone tissue morphometry in the craniotomy experiment resulted in a higher bone volume in the Treated group at 60 days (p <0.05, t student test). Microscopic and radiographic images demonstrate the formation of a bone bridge in the segmental defect, 60 and 120 days after surgery in the Treated group, different from the Control group with incomplete healing.
  • Polyvinyl alcohol (PVA) molecular weight and extrusion temperature in starch/PVA biodegradable sheets Original Article

    Zanela, Juliano; Bilck, Ana Paula; Casagrande, Maira; Grossmann, Maria Victória Eiras; Yamashita, Fabio

    Resumo em Inglês:

    Abstract The aim of this work was to study the relationship of chain size of partially hydrolyzed PVA blended with starch in properties of biodegradable sheets produced by thermoplastic extrusion. It was also studied the effect of extrusion temperature profile to determine the better PVA chain size and temperature profile to produce biodegradable sheets through a factorial design. The processability and the mechanical, thermal, optical, and microstructural properties of the biodegradable sheets were adequate, indicating that PVA/cassava starch blends have potential to replace conventional non-biodegradable polymers. Tensile strength and Young’s modulus ranges from 1.0 to 2.6 and 3.0 to 6.9 MPa respectively, the elongation at break ranges from 42 to 421%. It was not possible to state a conclusive relationship between PVA molecular weight and the materials properties, but in general, PVA with medium molecular weight and high extrusion temperature profile promote an increase of mechanical properties of the sheets.
  • Molecular dynamics studies of amylose plasticized with Brazilian Cerrado oils: part I Original Article

    Silva, Felipe Azevedo Rios; Sales, Maria José Araújo; Paterno, Leonardo Giordano; Ghoul, Mohamed; Chebil, Latifa; Maia, Elaine Rose

    Resumo em Inglês:

    Abstract Biodegradable polymers have become part of the realm of polymer science with specially when associated to renewable sources. Unraveling the plasticizer effect of natural occurring fatty acids in the Brazilian Cerrado on amylose oligomers was aimed in this work in an aqueous environment. Since the interactions within a material are of extreme importance to its molecular behavior, the main focus was directed to the molecular interactions whether intra or intermolecular type. Molecular Mechanics and Dynamics were carried out to shed light on this issue. The simulation results suggest the fatty acids could perform as efficient plasticizers for more complex polysaccharides such as starch. It also highlights the importance the solvation on the system stabilization, thus contributing to a clearer understanding of the chemical interactions role on plasticization. Our results provide a basis for simulating more complex systems such as a clay-mineral which will culminate in the parameterization for mesoscale studies.
  • Review of fungal chitosan: past, present and perspectives in Brazil Review Article

    Batista, Anabelle Camarotti de Lima; Souza Neto, Francisco Ernesto de; Paiva, Weslley de Souza

    Resumo em Inglês:

    Abstract Fungal chitosan is a polymer that has been discussed and studied since 1859 in the world with great advances occurring over the years. Due to its global importance, this review aims to expose the history of the production and application of fungal chitosan in Brazil. Data collection was done at the Scielo, Sciencedirect and Pubmed databases, considering the period of the last 50 years. The inclusion criteria were articles on pure or associated chitosan and, in particular, fungal chitosan produced or applied by Brazilian research groups. At the end of the review, it was noticed a fungal chitosan very studied in different continents, and in Brazil is still used in specific and small groups. With the present work, it is expected that the diffusion of the studies will be accelerated and that potential research groups for fungal chitosan may grow through interaction with the existing ones.
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