Resumo em Inglês:

Abstract The biodegradable aliphatic oligoester oligo(trimethylene separate) (OTS) was synthesized by polycondensation and used to plasticize poly(lactic acid) (PLA). Casting films of PLA and PLA/OTS with concentrations of 1, 5 and 10 wt.% were prepared, and these films were characterized by thermal analyses, crystallinity, rheology and mechanical tests. DSC revealed the decrease in the Tg of PLA films with addition of the oligomer and a partial immiscibility. Addition of OTS to PLA slightly decrease the thermal stability as well as increase the degree of crystallinity of these films. Dynamic-mechanical analyses of casting films showed that the PLA/OTS system presented lower storage modulus than PLA and mechanical test revealed an increased in the elongation at break for PLA films containing the oligoester. The results make possible to conclude that the oligomer synthesized from bio-based monomers acts as a plasticizer of PLA increasing the PLA ductility.

Resumo em Inglês:

Abstract This study investigated the effects of low concentrations of sericin (≤ 1.5 wt%) in starch- poly(butylene-adipate-co-terephthalate) (PBAT) films. The films were produced by blown extrusion and mechanical, barrier and structural properties were determined. Films containing 1.0 and 1.5 wt% sericin showed higher tensile strength (6.41 and 6.59 MPa) and Young's modulus (90.88 and 132.71 MPa) compared with film without sericin (4.76 MPa and 18.64 MPa). When 0.5 wt% of sericin was used, the elongation was reduced by 62%. The addition of sericin in a concentration of 1.5% (w/w) decreased the water vapor permeability of films from 7.55 to 5.94 g (m s Pa)-1, likely due to the formation of a more homogeneous and compact matrix. Based on these results, a mechanism of action is proposed, whereby sericin acts at the interface of the polymers (starch and PBAT), reducing the interfacial tension and enhancing compatibility.

Resumo em Inglês:

Abstract The aim of the study is to utilize the simplicity of oxidative polymerization with ferric chloride to originates poly(3-hexylthiophene) of lower molecular weight. So, the chloroform, in general used as solvent in this synthesis, was switched by dichloromethane. The obtained polymers were characterized by infrared spectroscopy (FTIR), ultra-violet visible spectroscopy (UV-Vis), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) were used to evaluate the structure, conjugation length, molecular weight and regioregularity with the goal of comparing these properties with those of poly (3-hexylthiophene) synthesized in chloroform. Despite large difference observed in molecular weight of polymers obtained by chloroform and dichloromethane, no significant differences were observed of these polymers in regioregularity and conjugation length.

Resumo em Inglês:

Abstract This article evaluates the efficiency of the degradation of pollutants present in water from the purification of biodiesel, characterized by high content of chemical oxygen demand (COD), suspended solids (SS), oils and greases, methanol, soap, and glycerol. The treatment process proposed was of the photo-Fenton type using iron immobilized in chitosan. The characterization of the material was performed according to degree of deacetylation (DD) and thermal stability (TG). The results revealed a DD of 66.5% and that the material undergoes decomposition in three temperature stages: 100; 150-350 and above 350 °C. The evaluated parameters were: COD, suspended solids, oils and greases, color and turbidity. After a 180-minutes long treatment, the removal percentage was 94.52, 70, 55, and 60% respectively. These results indicate that the photo-Fenton process can be an alternative for pre-treatment this type of effluent.

Resumo em Inglês:

Abstract In this research, palm oil and soy oil were used as a natural polyol to prepare novel poly(silyl ether)s. Palm oil and soy oil were first converted to monoglyceride by one step via alcoholysis process in the presence of 0.1% CaO as a catalyst. The monoglycerides were characterized by Fourier transform infrared spectrometer (FT-IR), nuclear magnetic resonance (NMR) and iodine test. The novel poly(silyl ether)s were prepared via polycondensation reaction between dimethyldichlorosilane with monoglycerides based on palm and soy oils, respectively. FT-IR, NMR and silicone-29 (29Si NMR) were used to confirm and determine the presence of silicone in the synthesized polymers. Thermal behavior was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Antibacterial activity of the polymers was screened against three different strains of bacteria, namely Escherichia coli E266, Staphylococcus aureus S276 and Salmonella choleeraesuis 10708.

Resumo em Inglês:

Abstract Proteins are frequently used as emulsifiers and stabilizers. In this work, two proteins with different isoelectric points were used: lactoferrin and ovalbumin. Solutions containing different proteins ratios, with different pH values, were stored for 7 days at 25 °C to analyze the system stability. Systems containing 3% w/v lactoferrin remained stable at all pH values studied, while systems containing 1% w/v ovalbumin remained stable only at a high pH value (8.0). Emulsions containing a mixture of proteins remained stable at a pH between the isoelectric points of the two proteins, which was attributed to an electrostatic bond because of the opposite charges of proteins at this pH. During the analysis of rheological properties, it was possible to observe a non-Newtonian behavior of the emulsions, using the models of Carreau and Cross to describe the pseudoplastic behavior of suspensions. This study provides important information for the use of functional ingredients.

Resumo em Inglês:

Abstract Advanced fabric reinforced polymer composites find extensive applications in aerospace and structural fields due to their high mechanical properties. A novel stamp forming technique finds extensive use in the hemispherical forming of thermoplastic composites. This study investigates the influence of stamp forming parameters on the formability of thermoplastic composite using Taguchi’s robust design and grey relational analysis. Taguchi’s orthogonal array was used for designing the forming experiments. Responses such as forming ratio and logarithmic thickness strain were considered for the assessment of sheet formability through single and multi-response optimization. Analysis of variance was used for the determination of the contribution of each parameter on formability and it was identified that the die temperature acts as a prominent factor, followed by blank holder force and blank temperature. The confirmation test was conducted at optimum parameter levels and the obtained experimental grade was seen within the confidence interval of the predicted value.

Resumo em Inglês:

Abstract This paper aims to evaluate the dosimetric characteristics of modified VIPARnd for radiotherapy dosimetry using optical investigations. The absorbance spectrum of the irradiated gel dosimeter was evaluated optically with spectrophotometer techniques and with a CMOS imaging system. The useful dose range for the peak value and the relative area under the absorbance curve is 3-20 Gy. The dose-response curve for CMOS readout has an interval of linearity from 3-20 Gy. The modified VIPARnd developed has a good dose range and good temporal stability in the spectrophotometric analysis of the intervals studied. The CMOS readout is transportable, cheaper, easier to use and an excellent alternative for dosimetry.

Resumo em Inglês:

Abstract Rubber blends are important materials in automotive industry, as well as in other sectors. However, there are implications when suitable use of a polymer in an artifact is not made. In the automotive area, for example, the use of an elastomer without the fuel resistance requirement would result in component degradation, potential fuel leakage, and danger of fire. The use of polymer blends may be the solution to this problem. Fourier transform infrared spectroscopy (FT-IR) can be used for the knowledge of the polymer content of these blends. Then, FT-IR quantitative methodologies for determining acrylonitrile-butadiene copolymer (NBR) copolymer and butadiene-styrene copolymer (SBR) contents were developed by the transflectance accessory, NIRA, and the transmission mode, being the sample analyzed by transmission and universal attenuated total reflection (UATR) in the medium infrared (MIR). UATR and NIRA methodologies showed better accuracy. However, the MIR analysis showed a detection limit between 10-20% of NBR.

Resumo em Inglês:

Abstract In the present work, the depolymerization of polyethylene terephthalate (PET) was performed by the method of glycolysis with ethylene glycol. The process was carried out using a factorial design in the Box-Behnken optimization model, using a response surface methodology (RSM) in which three factors (time, temperature and mass ratio of ethylene glycol) were studied in three levels of variation (- 1, 0, +1) with two replicates of the center point, totalizing 15 experiments for which the yield of bis (2-hydroxyethyl) terephthalate (BHET) monomers formed in the process was chosen as response. In parallel, the Arrhenius kinetic test was used to determine the apparent activation energy (Ea) for the 1-butyl-3-methylimidazole trichlorozincate ([Bmin]ZnCl3) - catalyst used in the depolymerization process. The products of glycolysis obtained were characterized by spectroscopic techniques (FTIR), (1 H and 13C NMR), thermal analyses (TGA) and (DSC) and Mass Spectrometry LC-MS/MS hybrid Quadrupole-Orbitrap.

Resumo em Inglês:

Abstract Core-shell magnetic polymer particles were synthesized by seeded suspension polymerization. The core was made of poly(methyl methacrylate-co-divinylbenzene) and a mixture of magnetite, maghemite and goethite (P(MMA-co-DVB)-M). The shell was composed of poly(glycidyl methacrylate-co-divinylbenzene) (P(GMA-co-DVB)). These particles were characterized by infrared spectrometry (FTIR), thermal analysis (TG), scanning electron microscopy (SEM), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The results showed the formation of core-shells with good magnetic properties (≈7.1 emu/g) and good thermal resistance (≈300 ºC). The light scattering experiments showed that the particle size of these materials changed from 5-90 microns (core) to 5-120 microns (core-shell). Scanning electron microscopic images were useful to show the formation of P(GMA-co-DVB) shells on P(MMA- co-DVB)-M cores. The materials synthesized in this work have potential to be modified and employed in magnetic separation processes in the biotech and environmental fields.

Resumo em Inglês:

Abstract Gelatin is employed in pharmaceutical applications because of its biodegradability, biocompatibility and low toxicity. However, it may be necessary to promote gelatin crosslinking in order to develop drug release systems and extend release times. SEC analyses are used here for the first time to monitor the evolution of molar mass distributions of gelatins during treatment with glycerol and glucose in dispersed media. Unambiguous experimental evidence of gelatin crosslinking in presence of sugars and glycerol has yet to be presented. SEC results indicate that average molar masses decrease during gelatin treatment, while FT-IR analyses indicate that gelatins are subject to structural modifications during processing, which can explain the decrease of gelatin solubility after treatment. The results presented here indicate the importance of using SEC techniques to monitor gelatin crosslinking, as they seemingly contradict previously published results that make use of indirect measures for this purpose.