Resumo em Inglês:

Abstract This work reports the spectroelectrochemical and electrical behavior of electropolymerized donor-acceptor like (D-A) copolymer films, based on 3,4-ethylenedioxythiophene (EDOT) and beta-substituted electron-acceptor thiophenes. Initially, the copolymer films were deposited on indium tin oxide substrates, which spectroelectrochemistry measurements were carried out with an UV-Vis spectrophotometer. Hence, it was possible to observe the electrochromic properties of these materials, visualizing the color changing towards different potentials applied. The experiments have shown that these D-A like copolymers presented good electrochromic properties, such as optical contrast, coloration efficiency, and switching times. Additionally, films prepared on a platinum working electrode were investigated by electrochemical impedance spectroscopy, which has shown the electrical behavior of those copolymers and their potential as candidates to capacitive devices building. Therefore, the combination of electron-donor EDOT with those electron-acceptor monomers is indeed a useful strategy to tailoring and fine-tuning the physicochemical properties of polythiophenes with innovative applications.

Resumo em Inglês:

Abstract Antistatic packaging is a very important sector since the electrostatic discharge of electronic devices can damage and/or disable these products. In addition, it is essential to dispose of this packaging correctly. In this work, the synergistic effect of the addition of lignin and carbon black on the development of antistatic and biodegradable packaging was verified. In this study, PLA was mixed with lignin and carbon black and the composites were prepared using a high-speed thermokinetic homogenizer where the melting of the PLA and the blend with fillers occurred by friction. The composites were characterized by Izod impact tests, scanning electron microscopy, thermal properties, electrical characterization and biodegradation tests in garden soil. The results show that lignin is a great option to accelerate the biodegradation of PLA in the garden soil and the carbon black acts as an antistatic agent reducing the electrical resistivity of the composites.

Resumo em Inglês:

Abstract The solidification of a thermoplastic during the injection process directly influences the productivity and quality of the final product. This paper presents a study of the solidification performance of parts produced by a thermoplastic injection process, verifying their dimensional, visual, and production behavior according to the variation of geometry, temperature, and design of the injection mold cooling system. SolidWorks Plastics® software was used to perform the simulations. Experiments were performed with a plastic injection mold to confront and validate the simulations. Given the comparison of different cooling geometries, the simulations made it possible to obtain parts with a shorter mold cooling cycle time. Payback analysis has the primary objective of determining which cooling system is the most viable and has the highest return on invested capital. The results demonstrated a solution for engineers and designers to justify maintenance or modifications to existing injection molds through numerical simulation.

Resumo em Inglês:

Abstract Electrospun nanofibers from gelatin (G), chitosan (CS), and chitosan-polyvinyl alcohol (CS-PVA) were developed by electrospinning process. Mechanical properties were determined by the tensile test, the elastic modulus values of the nanofibers were G (15.418-34.34 MPa) and CS-PVA (17.44-126.427 MPa). The morphological characterization by SEM revealed that the systems with 15% G and 6% CS-PVA showed morphological homogeneity. Structural characterization by FTIR indicated an interaction among some functional groups of the component. Thermal analysis by DSC and TGA showed degradation temperatures for G (330 °C), CS (210 °C to 370 °C), and PVA (310 °C to 420 °C). The contact angles values denoted the hydrophilic nature of the material. Finally, the antimicrobial assay proved that both 15% G and 7% PVA on the CS-PVA system presented the best antimicrobial effect. The results indicate that the electrospun nanofibers fabricated with G or CS-PVA can be used as wound healing dressings.

Resumo em Inglês:

Abstract The crosslinking of the Fc fragment (IgG antibody) on a polymer matrix about of dimethylacrylamide (DMA), melamide group (MG) and n-acryloxy succinimide (NAS) was analyzed through Monte Carlo simulation at 277.15K and pH 7, in where Gibs free energy and the dipole moment indicated the spontaneity of the reaction through van der Waals interactions. In addition, the QSAR properties determinated that both the surface area and the volume allow to carry out the physical adsorption of the Fc fragment that was verified through the electronic distribution of the electrostatic potential maps (MESP) where the nucleophilic zones (blue color) and electrophilic (red color) were observed, while the partition coefficient (Log P) indicated the solubility of the process. Subsequently, the analysis of the adsorption of the terbium ion (Tb+3) at 277.15K and a pH 7 in Fc/polymeric matrix was carried out, observing that the Fc fragment presented a flat-on optimization geometry attributed to the Tb+3 that generates electronic repulsions, as well as van der Waals forces, hydrogen bonds derived from the Cys aminoacids formed a polar structure and that was corroborated by the Log P negative. Finally, the surface area and volume determined that Tb+3 adsorption showed an increase in surface area and volume with temperature.

Resumo em Inglês:

Abstract Melamine is a key compound used as a clarifying agent for waste lubricating oil primarily due to its excellent adsorbent properties. Moreover, considerable interest exists for the further modification of melamine in order to provide a remediation agent with improved clarification capacity. In this study, hexamethylolmelamine was prepared using a solution of formaldehyde, which provided an agent capable of incorporation into a silicate polymer framework. Subsequently, the resultant monomer was added to a solution of silicate to produce the melamine-silica polymer. The melamine and melamine-silica polymer were characterized using the techniques of XRD, FTIR, SSA and thermal analysis to confirm structural and morphological characteristics. These characterizations indicated that the increase in the surface area of the 0.315 m2/g to melamine to 26.71 m2/g of melamine-silica suggests the effective introduction of silanols groups to hexamethylolmelamine and, therefore, corresponds to thehigh performance in relation to melamine as clarifying of waste lubricant oil.

Resumo em Inglês:

Abstract Microcrystalline cellulose synthesized from the waste of Musa balbisiana (BMCC) was characterized to explore the possibility of application in the pharmaceutical industry especially as a drug delivery vehicle. The SEM, XRD and FTIR investigations revealed that the predominantly short, non-aggregated and irregular MCC rods were highly crystalline. The moisture sorption value for BMCC was 5.65%, while total ash was 0.39%. Flow of BMCC was poor, but the product exhibited high hydration (11.7%) and swelling (277.0%) capacities. Preliminary investigation of BMCC tablets containing ascorbic acid carried out in simulated intestinal fluid, showed a concentration dependent retardation of drug release. No cytotoxicity of BMCC was observed in the hemolytic assay. Overall, the study revealed that BMCC can be prepared from an inexpensive and abundant agricultural waste and possesses properties advantageous for application in the pharmaceutical industry and may be explored further in drug delivery research.

Resumo em Inglês:

Abstract This work investigated the effect of thermal treatment in an autoclave on the chemical, physical, and morphological properties of lignocellulosic fibers from açaí (Euterpe oleracea Mart), and the behavior of this treated fiber in polypropylene (PP) matrix composites with polypropylene-graft-maleic anhydride (PPgMA) as the coupling agent. The treated and untreated fibers were characterized by chemical composition, x-ray diffraction, FTIR spectroscopy, and thermogravimetry, scanning electron microscopy and tensile tests were carried out for the composites. The results showed that the thermal treatment modified the hemicellulose and lignin content and increased the fiber surface roughness, without compromising the thermal stability. The composite prepared with thermally treated fibers and PPgMA exhibited an increase in tensile strength but a reduction in tensile modulus. In conclusion, the thermal treatment of vegetable fiber is a promising technique for improving the performance of composites.

Resumo em Inglês:

Abstract A platinum electrode (Pt) was coated with poly(2-hydroxyethyl methacrylate) (PHEMA) by electrochemical polymerization using chronopotentiometry. Electropolymerization of polyaniline nanowires doped with camphorsulfonic acid (PANI:CSA) was further performed on the surface of the Pt-PHEMA electrode by cyclic voltammetry. The coated Pt-PHEMA-PANI:CSA electrode was characterized by Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). According to EIS, the Pt-PHEMA electrode exhibits a charge transport resistance (Rct) of 169.19 kΩ. The EIS analysis of Pt-PHEMA-PANI:CSA electrode reveals a less resistive character (Rct=1.28 Ω) than the observed for the Pt electrode coated with PANI:CSA (Rct=0.47 kΩ). As demonstrated by SEM, the Pt-PHEMA-PANI:CSA electrode has a high surface area due to the PANI:CSA nanowires embedded in Pt-PHEMA. The biocompatibility of PHEMA, allied to the electrochemical characteristics of PANI:CSA, could be useful to the development of implantable electrodes for biomedical applications.

Resumo em Inglês:

Abstract In this paper was investigated the chemical, physical, thermal, mechanical and morphological characteristics of the recyclable materials obtained of the NESCAFÉ® DOLCE GUSTO® branded beverage capsules, characterizing different resulting compositions. The characterization was made by following techniques: Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Water Absorption and techniques for the analysis of mechanical properties (tensile and impact test). The results showed that the body of the capsule and the inner filter, both made of polypropylene, are the most interesting materials to be reused, having good properties, while the materials resulting from the mixtures of all the constituents in the beverage capsules presented decreased mechanical properties.

Resumo em Inglês:

Abstract This study aims to evaluate the effects of natural weathering in the city of Teresina, State of Piauí, Brazil, on the morphology and mechanical properties of eco-composites based on high-density green polyethylene, powdered cork and compatibilizer processed in a twin-screw extruder and injection molded. The analyses revealed that although weathering induced surface bleaching of eco-composites and cracking, these effects were not intense in the compatibilized samples. The tensile properties of the investigated materials were affected by abiotic degradation, which led to a reduction of the tensile strength and elastic deformation of the eco-composites, however, the incorporation of PEgMA was fundamental for the maintenance of mechanical performance after natural aging. In general, the results obtained were satisfactory for external applications of the compatibilized eco-composite with 15% cork in the proposed weathering range, which indicates its possible use in temporary constructions.

Resumo em Inglês:

Abstract A Bio composite comprising Prosopis Juliflora Fiber (PJF) and Poly Lactic Acid (PLA) was processed considering two particulate sized reinforcements, coarse PJF (avg. 15 µm) and fine PJF (10-50 nm). They were added individually at ratios of 10, 15, 20 and 25 wt% into PLA matrix. The composites were extruded and tested for mechanical properties. The addition of PJF resulted with an increase in the tensile, flexural and impact strengths of the polymer. Adding PJF to PLA showed a decrease in the hardness of the polymer. Water Absorption test showed an increase in water uptake with increasing fiber content. The most optimum ratio of PLA to PJF was found to be 80:20. The fine PJF reinforced composites proved to be superior over the coarse PJF reinforced composites at all stages of the research. FESEM and TGA were used to study morphology and thermal characteristics respectively.