Resumo em Inglês:

Abstract The aim of the work was to study the mechanical properties of extruded starch/polyvinyl alcohol (PVA)/glycerol biodegradable blends using multivariate analysis. The blends were produced as cylindrical strands by extrusion using PVAs with different hydrolysis degrees and viscosities, at two extrusion temperature profiles (90/170/170/170/170 °C and 90/170/200/200/200 °C) and three conditioning relative humidities of the samples (33, 53, and 75%). The mechanical properties showed a great variability according to PVA type, as well as the extrusion temperature profile and the conditioning relative humidity; the tensile strength ranged from 0.42 to 5.40 MPa, elongation at break ranged from 10 to 404% and Young’s modulus ranged from 0.93 to 13.81 MPa. The multivariate analysis was a useful methodology to study the mechanical properties behavior of starch/PVA/glycerol blends, and it can be used as an exploratory technique to select of the more suitable PVA type and extrusion temperature to produce biodegradable materials.

Resumo em Inglês:

Abstract In this work, conductive polymers were prepared based on polypyrrole (PPy) and its blends with epoxy resin. The chemical syntheses of PPy used two oxidants (Fe2(SO4)3 and FeCl3.6H2O) and two surfactants (DBSNa and DBSA). PPy samples and their blends were characterized by scanning electron microscopy, electrical conductivity by four points, and measurements of complex parameters of electric permittivity (ε) and magnetic permeability, in the frequency range of 8.2 to 12.4 GHz. The micrographs of the fractured surfaces show that the PPy synthetized in the presence of surfactants has particles with smaller diameters, and the oxidant sulfate favored the formation of elongated structures, called fillets. The analysis of the blends found a homogeneous distribution of PPy clusters in epoxy resin matrix, which did not favor the electrical conductivity of these materials. On the other hand, the measurements of the complex parameters of the permittivity show that the blends have increasing values when the PPy concentration is increased in the epoxy resin.

Resumo em Inglês:

Abstract Encapsulation of bioactive compounds has been carried out to improve bioavailability and to protect them against harm conditions. However, encapsulation processes are often aggressive and it is important that encapsulated substances keep their biological activity. In this work curcumin was nanoencapsulated using dichloromethane as solvent and ultrasound as dispersion device. Nanoparticles were obtained using different curcumin concentrations and encapsulants (PLLA and Eudragit S100) and the encapsulation efficiency was inferred using spectroscopic and calorimetric techniques as well as optical microscopy. Total phenolic contents and antioxidant activity tests were applied to the curcumin before and after encapsulation and also to blank polymer nanoparticles. Results demonstrated that the encapsulation process had no deleterious influence on its antioxidant activity.

Resumo em Inglês:

Abstract The rheological properties of acrylic paints and polyaniline (PAni) blends, with different contents of PAni doped by dodecyl benzene sulphonic acid (DBSA) and, dispersed by mechanical stirrer and ultrasonic, were investigated by controlled shear rate testing ramps. The results showed that the commercial acrylic paint had tended to deliver the required stability on the blends, in order to avoid sedimentation process. All samples exhibited non-Newtonian flow behavior (shear thinning), increasing PAni content the flow behavior index (n) decreased (0.41 to 0.11) and power law model were used to fitted the experimental curves. The results showed that the addition of PAni-DBSA affects the viscoelastic behavior of the mixtures due to the interactions between the components in the mixture. The best properties were obtained for samples 90/10 wt % dispersed by ultrasonic, indicating the feasibility of the usage as a conducting paint.

Resumo em Inglês:

Abstract Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO2), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO2 does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO2. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials.

Resumo em Inglês:

Abstract The effects of the polypropylene-grafted maleic anhydride (PP-g-MAH) and polypropylene methyl polyhedral oligomeric silsesquioxane (PP-POSS) compatibilizers on the mechanical, thermal and physical properties of palm kernel shell (PKS) reinforced polypropylene (PP) were investigated. The production of PP/PKS biocomposites was performed by melt mixing using Brabender Internal Mixer. Mechanical test results showed that the biocomposites with PP-g-MAH have better tensile strength compared to biocomposites with or without PP-POSS. The results also showed an increase in the tensile strength and elongation at break when compatibilizers were added. Polypropylene-grafted maleic anhydride improved the Young’s modulus of the biocomposites, but PP-POSS reduced it. Moreoever, adding compatibilizers in biocomposites reduced the water absorption of the biocomposites. The compatibilizers improved the nucleating ability of filler in the composites. The PP-g-MAH compatibilizer provided better performance in improving nucleating ability to biocomposites compared to PP-POSS.

Resumo em Inglês:

Abstract Low cost UV-Ozone reactor using a high pressure mercury vapor lamp of 80 watts without outer bulb showed good results for treatment of ITO films used as anode electrode in the assembly of P-OLED (polymer-organic light emitting diode) devices. This study revealed 20 minutes as effective treatment time and it was verified also that the effect of UV-Ozone treatment loses its efficiency as the elapsed time increases. It was analyzed with measurements of contact angle using a droplet of PEDOT:PSS polymer. P-OLEDs devices were mounted with architecture: ITO/PEDOT:PSS/PVK/Alq3/Al. The PVK polymer was diluted in organic solvent of 1,2,4-trichlorobenzene with concentrations of: 5, 10, 20 and 30 mg/mL. Results revealed better performance of P-OLED devices for concentration of 5 mg/mL resulting in lower threshold voltage, elevation of electrical current and similar diode curve.

Resumo em Inglês:

Abstract This work describes the synthesis of new ion-imprinted polymers (IIPs) for selective solid phase extraction of Zn(II) ions from aqueous samples. IIPs were synthesized by copolymerization of salicylic acrylate (SA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a crosslinker in the presence of 2,2’-azobisisobutyronitrile (AIBN) as an initiator. The template ions were removed from IIPs particles by leaching with 0.1 M Ethylenediaminetetraacetic acid (EDTA) which leaves cavities in the particles with the capability of selective extraction of the Zn(II) ions. The monomer and the polymer after synthesis have been characterized by 1H NMR, 13C NMR and FT-IR studies. The effect of the pH on the extraction efficiency of Zn(II) ions was studied and optimized in pH around 6. The selectivity of the synthesized IIPs was studied in the presence of Co(II), Cd(II) and Ni(II) ions, and the IIPs showed higher affinity for Zn(II) in the presence of other interfering ions.

Resumo em Inglês:

Abstract This work aims at studying not only the rheological behavior of natural rubber-based compositions by making use of different contents of fluoromica or ME 100 synthetic mica in a natural rubber (NR) matrix, but also the different filler-filler and matrix-filler interactions before and after curing. The ME 100 content in NR varied from 0 to 10 phr (parts per hundred parts of resin) and the results enabled to conclude on the influence of the mineral filler on the curing parameters, as well as on the limit amount of ME 100 for the best performance resulting from the best filler distribution/interaction in the polymer matrix. All data were compared with those of the unfilled composition. Based on complex viscosity, curing parameters, dynamic modulus and Payne effect tests it was concluded that the mica content limit for the best performance was 7 phr.

Resumo em Inglês:

Abstract New functional polymers will be prepared using alkyd resins having high solid content (environmentally friendly) and comb-type structural morphology. Different copolymers of hydroxyethyl acrylate and methyl methacrylate (HEMMA) were synthesized by solution polymerization using azo-bis-(isobutyronitrile) (AIBN) as initiator and dimethylformamide as a solvent. The proportions utilized of AIBN were 0.5 (HEMMA1), 1.0 (HEMMA2), 1.5 (HEMMA3) and 2.0 wt. % (HEMMA4). The conversion percentage of the reaction was higher than 90%. The formation of the copolymers was evidenced by infrared analysis, hydroxyl value, and nuclear magnetic resonance. The intensity of OH group adsorption increased with the molecular weight and hydroxyl value. The polydispersity index was lower than 1.5. All copolymers exhibited a stable region on viscosity at a shear rate between 0.1 and 10 s–1. The copolymers exhibited good thermal stability, flexibility, and adherence.

Resumo em Português:

Resumo O presente trabalho visa apresentar resultados da aplicação de uma resina epóxi bisfenólica (DGEBF) à base de nanopartículas de sílica (RN) e comparar suas propriedades com a resina convencional de referência epóxi bisfenólica (DGEBA) (RE), atualmente utilizada. Neste sentido fabricaram-se protótipos de barras estatórica, destinadas a hidrogeradores, através do sistema VPI (Vácuo-Pressão-Impregnação) e avaliaram-se as propriedades elétricas pelas técnicas de fator de dissipação e envelhecimento acelerado. Dentre os resultados para as resinas observou-se que: (i) o fator de dissipação e de envelhecimento são praticamente os mesmos para ambas as resinas; (ii) o valor de tip-up resultaram em 0,014% para RE e 0,020% para a resina RN e (iii) a estimativa do tempo de vida útil esta em cerca de 40 anos, o que é aplicável para a maioria das aplicações industriais. Neste sentido sugere-se que a resina RN pode ser uma alternativa a resina RE, com um desempenho elétrico equivalente.

Resumo em Inglês:

Abstract The present work aims to present the results of an application of a bisphenolic epoxy resin (DGEBF) containing silica nanoparticles (RN) and compare its properties with a bisphenolic epoxy resin (DGEBA) (RE), currently used. In this context, prototype stator bars for hydrogenerators were manufactured, according to the VPI (Vacuum-Pressure-Impregnation) system and their electrical properties with the tests of dissipation factor and voltage endurance. Within the results for the resins it was observed that: (i) dissipation factor and voltage endurance are practically the same for both resins; (ii) the resulting values of tip-up were 0.014% for RE and 0.020% for RN resin and (iii) the estimating of the life-time is about 40 years, what is suitable for most industrial applications. In this sense it is suggested that the RN resin can be an alternative to the RE resin, with an equivalent electrical performance.

Resumo em Português:

Resumo A aplicação de polímeros biodegradáveis para encapsular pesticidas é uma estratégia que permite, a partir de diferentes proporções entre os polímeros, modificar o perfil de liberação do agente. Este trabalho avaliou a liberação controlada do pesticida cipermetrina encapsulado em microesferas de blendas de P(3HB)/PCL (100/0, 0/100, 97/03, 95/05, 90/10, 80/20 e 70/30) obtidas pelo método de emulsificação-evaporação do solvente. As imagens de microscopia eletrônica de varredura revelam a forte influência da PCL na porosidade das microesferas. As análises de infravermelho mostraram a presença do pesticida em todas as composições de polímeros avaliadas. O ensaio de liberação de cipermetrina sugere que, no intervalo de 4 horas, o teor de cipermetrina liberada é dependente da composição das blendas utilizadas. As microesferas de PHB e blendas com menores teores de PCL, 97/03 e 95/05 liberaram 75% a 85% enquanto a composição 70/30 liberou 100% de cipermetrina.

Resumo em Inglês:

Abstract This work evaluated the controlled release of cypermethrin pesticide loaded in microspheres of P(3HB)/PCL blends obtained by emulsion-evaporation method. SEM analysis revealed a strong influence of PCL on the porosity of the microspheres. The infrared spectra showed the presence of pesticide in all polymer compositon evaluated. DSC curves showed that with higher content of PCL, decreased the crystallinity degree of polymers, resulting in a faster release of the pesticide. The release assay of cypermethrin suggests that within an interval of four hours the amount of pesticide released varies depending on the composition of the blends.