Resumo em Inglês:

Abstract Virgin polystyrene (PS) composites were reinforced with medium density fiberboard (MDF) residue, considering the influence of fiber content. The composites were evaluated for their morphology, identification of functional groups and thermal behavior. Mechanical tests and a degradation study under ultraviolet radiation (UV) were also performed. The results showed that the best properties were obtained for composites with 4% by mass of MDF waste. The addition of residue was found to increase thermal stability of polystyrene compared to its pure form. The morphology of the composites showed homogeneity of the material. In the degradation tests under ultraviolet (UV) radiation, it was found that the presence of MDF residue slows down the matrix degradation process when evaluated by means of tensile strength. Polystyrene composites reinforced with MDF residues showed good mechanical properties and can be applied in the development of materials that do not need a good appearance.

Resumo em Inglês:

Abstract In this work, a bio-based adhesive is prepared from Protium heptaphyllum resin. The resin is first characterized by 1H and 13C nuclear magnetic resonance spectroscopy and the bioadhesive is then prepared using a simple mixture of the resin with linseed oil, catalyzed by cobalt octanoate, to induce crosslinking. The precursors and bioadhesive obtained are characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The NMR analysis shows the presence of groups of triterpenes, such as α- and β-amyrins, and diols, such as brein and maniladiol. Thermogravimetric analysis reveals that the resin has less thermal stability than the bioadhesive. Mechanical tests indicate that the bioadhesive has greater adhesion strength compared to the commercial adhesive, reaching an average stress at break of 7.66 and 0.113 MPa for the wood and carbon steel substrates, respectively. In conclusion, the bioadhesive can be used for the production of composites.

Resumo em Inglês:

Abstract In the study, sweetgum tree (Liquidambar orientalis), which is an endemic species that grows in Mugla, Köyceğiz and is applied for medicinal purposes among the public, its leaves was examined. The antioxidant ability of the extract obtained from dried plant leaves has been evaluated using a variety of methods which are Total Phenolic Substance, Total Flavonoid, FRAP, CUPRAC, DPPH, and ABTS+. Simultaneously, the antimicrobial activity of the plant extract was examined using disk diffusion and microdilution methods to determine the minimum inhibitor concentration (MIC). While the total phenolic content of Liquidambar orientalis extract was 96.34 mg GAE/g, the total amount of flavonoid was 2.15 mg QE/g. When the results of the antioxidant analysis were examined, it was observed that it had a good level of antioxidant activity with the results of 49.25 ± 0.54 mmol TEAC/g according to the CUPRAC method, 39.83 ± 0.25 µmol Fe/g according to the FRAP method, 80.34 μg/mL according to the DPPH method and 51.20 μg/mL according to the ABTS+ method. As a result of the antimicrobial analysis, it was indicated that L. orientalis extract was more effective on Staphylococcus aureus (S. aureus), which is a gram-positive bacterium and causes a wide variety of clinical diseases. Even, L. orientalis extract with an MIC value of 10 mg/mL has been found to have a higher antibacterial effect than Amoxicillin+Clavulanic acid, which is used as a standard drug in that field. This research is significant because it is the first to report the determination of all biological activities for L. orientalis, including total polyphenols, flavonoid contents, antioxidant content, and antimicrobial activity.

Resumo em Inglês:

Abstract This study aimed to evaluate the process of cellulose extraction from yacon stem using combined pulping and bleaching processes to produce nanofibrillated cellulose (NFC). First, a chemical pulping process with NaOH was applied and, subsequently, the pulp obtained was bleached. From the chemical pulp (CP) bleached, NFC was obtained by the mechanical defibrillation in a colloidal grinder. Then, chemical composition, and infrared analysis of the pulps were performed. The pulping process showed a lower amount of extractives and lignin content, as a low yield and an excessively dark pulp. The CP bleached with NaClO2 showed the best results increased whiteness of the pulp. A suspension of NFC with fibers of 5-60 nm in diameter, high crystallinity index, and thermal stability was obtained. The results are promising and demonstrate the technical feasibility of obtaining NFC from yacon stems waste which is ideal to apply to other materials of the industry.

Resumo em Inglês:

Abstract Recycling systems are unable to remove efficiently all potential contaminants acquired along the recycling chain. Therefore, contaminants may potentially exist in recycled food packaging. The safety of recycled cellulose food-contact materials depends on the toxicity and the ability of post-consumer contaminants to be absorbed by recycled fibers released by the packaging and ultimately absorbed by the food. Furthermore, the migration of different contaminants is related to their levels of contamination, structures and chemical affinity with cellulose fibers. In this study, twenty samples of cellulose packages available in the Brazilian market were evaluated regarding migration of phthalates (dibutyl phthalate – DBP, diisobutyl phthalate – DIBP and bis(2-ethylhexyl) phthalate – DEHP) and 2,6-diisopropylnaphthalene – DIPN into fatty food simulant using GC-FID. Fifty percent of the cellulose packaging samples showed no migration of DIPN or of any phthalates evaluated, whereas 20% showed migration of DIBP, 15% migration of DBP and 40% migration of DEHP.

Resumo em Inglês:

Abstract The protein adsorption on the porous alginate microparticles was evaluated in regards to the coating ability and this protective effect during gastrointestinal assay. The coating was performed at suitable pH for optimized electrostatic interaction between protein and alginate. Concentrations of gelatin (HGE) and their hydrolysates (Collagel® (MGE) (> 10 kDa) and Fortigel® (LGE) (3 kDa)) from 1 to 10% (w/w) were tested. Higher protein adsorption was observed in the highest concentration of protein in solution and the amount adsorbed was inversely proportional to the degree of hydrolysis with 47.3, 41.4 and 29.3% of protein adsorbed when HGE, MGE and LGE were used, respectively. The particles that showed higher protein adsorption were submitted to gastrointestinal in vitro assay. In gastric simulation, 39.1, 41.8 and 49.0% of protein from HGE, MGE and LGE were solubilized while 81.3, 61.5 and 95.2% were solubilized after 5 h under enteric conditions.

Resumo em Inglês:

Abstract To produce polysaccharide-based hydrogels and cerium (Ce3+) doped hydroxyapatite plus chitosan and collagen to enable future applications in the treatment of joint degeneration. Hydrogel production and characterization were performed with Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and cytotoxicity testing with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]. A final biomaterial composition was Kelcogel® Gelana (58%), chitosan (22.3%), Ce3+ doped hydroxyapatite (10.7%) and bovine collagen (9%), or selected aspect material gelatinous physical color with whitish color and can be injected. The biomaterial composition was proven in the FTIR and TGA, which also provided the maximum supported temperature. In the MTT assay, despite the reduction in viability of the experimental group compared to the control group, cell viability remained approximately 90%. In the FTIR and TGA tests, the material composition was proven. The material does not present cytotoxic behavior for the MTT test, being an alternative for the treatment of joint diseases.

Resumo em Inglês:

Abstract A new oleic acid derivative plasticizer, epoxidized trimethylolpropane trioleate (EPO), has been synthesized and its application in PVC formulations compared with di(2-ethylhexyl) 1,2-cyclohexanoate (DOCH/DEHCH), a commercial phthalate-free plasticizer of petrochemical origin. EPO and their blends with DOCH were added to PVC resin (50 PHR) and the plasticized PVC has been characterized by thermal and mechanical measurements. EPO demonstrated good compatibility with the PVC resin improving the thermal stability and elongation at break. Due to EPO high molar mass, a slight increase in the glass transition temperature and hardness was observed as the content of EPO in the plasticizer blend increased. The results indicate that EPO is a potential plasticizer for PVC when pure and, by replacing 50% of DOCH, the PVC compound shows similar properties to pure DOCH, but better elongation at break and thermal stability.

Resumo em Inglês:

Abstract A silane coupling agent, namely γ-aminopropyltriethoxysilane (APS), was used to modify kenaf powder (KP). It was then used as filler in a thermoplastic elastomer (TPE) based on Recycled High Density Polyethylene/Natural Rubber Blends (rHDPE/NR). The attachment of silane onto KP was verified by Fourier Transform Infrared Spectroscopy (FTIR), while the performance of the TPE was assessed in terms of mechanical and thermal properties. The results revealed that specific functional groups of APS were efficiently grafted onto the KP. Tensile strength was improved by the modification with silane and this also affected Young’s modulus of the TPE. Also, improved thermal stability was confirmed by thermogravimetric analysis (TGA), as the degradation temperature increased upon inclusion of silane. These effects are attributed to improved compatibility of the KP and rHDPE/NR blend. Such compatibilizing effect was confirmed by Differential Scanning Calorimetry (DSC) that indicated significantly increased crystallinity after the modification with silane.

Resumo em Inglês:

Abstract Fused Filament Fabrication, better known as Fused Deposition Modeling®, is currently the most widespread 3D Printing Technology. There has been a significant demand for developing flame-retardant filaments. Thereby enabling them, for example, in electronics and automotive applications. In this study, commercial PLA filament was modified by the addition of 1, 3 and 5% (%wt.) of expandable graphite. The composites were reprocessed, via extrusion, into filaments for Fused Filament Fabrication. Thermal properties of the filament composites were evaluated by thermogravimetric analysis and differential scanning calorimetry. Mechanical properties of thermo-pressed specimens indicated that no strong adhesion was promoted between the filler and matrix. This is a challenge with expandable graphite reported by many authors. All composites with expandable graphite achieved the V-2 rating of UL-94 flammability test. In spite of this, the results indicated that flammability of the PLA was reduced. All composite filaments were printable and prototypes were successfully 3D printed.

Resumo em Inglês:

Abstract Environmental concerns and the urgent need for reduction of fossil fuel consumption motivate materials research towards increased transportation efficiency. This work investigates the possibility of reducing the weight of electrical cables in automotive applications by replacing part of the metallic screen with electrically conductive polymer/carbon nanotube (CNT) nanocomposites. PP and PA12 were tested as possible matrices and the melt processability of the composites prepared by melt mixing was assessed for compositions up to 4 CNT wt. %. The tensile and flexural mechanical properties, the electrical conductivity, as well as the electromagnetic shielding effectiveness were evaluated. The performance of PA12/CNT composites was much higher than that of PP/CNT equivalents, due to better dispersion. It was demonstrated that, at industrial production scale, these materials could achieve a reduction of 4-20 weigth % relative to a standard automotive cable.

Resumo em Inglês:

Abstract This study was designed to investigate physical properties such as color changes after weathering and water absorption (WA) levels, and combustion performance of borates-impregnated and LG-coated Oriental beech wood. Results showed that borates impregnated and LG-coated Oriental beech wood showed positive lightness stability after weathering. The best color stabilization was obtained with LG-coated Oriental beech. Except for the 1 h WA period, LG did not show a water repellent effect after the water absorption test. Borates impregnation before LG-coating caused to decrease in weight loss of Oriental beech after the combustion test. Moreover, the lowest weight losses were obtained in borate impregnated Oriental beech wood.