Resumo em Inglês:

Abstract Waste mango was used to obtain starch and micro-cellulose for the production of bioplastic. Three different formulations were made: positive control or cotyledon starch/glycerol; SC1 or cotyledon starch/glycerol and cellulose at 0.1% and SC5 or cotyledon starch/glycerol and cellulose at 0.5% w/w. The bioplastics were mechanically analyzed (tensile strength, elongation and Young´s modulus) and, aerobic biodegradation analysis was realized with a standard test method based on the amount of material carbon converted to CO2. The mechanical tests indicated that with the addition of cellulose, the bioplastics improved their mechanical properties. The biodegradation at 30 days showed 93 and 94% for SC1 and SC5. Therefore, the biodegradation of bioplastics depends on both, the addition of cellulose and the environment where they are placed (e.g., soil characteristics: pH level, C:N ratio, moisture). These bioplastics offer new opportunities for fast degrading biomaterials in agricultural applications (padding and protection bags).

Resumo em Inglês:

Abstract In this study, the influence of carbon black (CB) trimodal mixture, with different medium particle sizes, on the colorimetric and rheological properties of polyethylene was evaluated. Three different types of CB were selected, with particle sizes of 15nm (S), 38nm (M), and 75nm (L) and combined, generating a Design of Experiments (DOE) with 19 formulations to be dispersed at 30% in low density polyethylene (LDPE) in twin screw extruder. Such formulations were evaluated in performance and process properties, such as Tint Strength, Melt Flow Index (MFI), and Total Transmittance (TT). It was observed that the mixtures between small (S) and medium (M) particles developed greater tinting strength and lower viscosity, demonstrating the synergy of the mixture, which was superior in the performance of the mixture containing only a particular of 15nm (S) that would have greater potential for results.

Resumo em Inglês:

Abstract In this work eggshell membrane was added as biobased curing catalyst to epoxy (DGEBA), for comparison purposes the synthetic catalyst DEH 35 data was reported, the curing of compounds was followed through differential scanning calorimetry (DSC) under dynamic conditions and their kinetics were modeled using Kissinger, Friedman, Friedman model based and Málek approaches. From evaluated Ea and ln A two steps of curing were verified, for the synthetic catalyst compound (S5) Ea abruptly increased for the degree of conversion α>0.7 the opposite trend was observed for the eggshell membrane compound (M10). It is supposed for S5 Ea increases due to the competitive reactions leading to viscosity increase until reach the solid phase with decrease of the reactive groups availability, hampering the cross-linking, whereas for M10 Ea decreases at α>0.7, hence invalidating the Kissinger model which assumes constant Ea.

Resumo em Inglês:

Abstract This paper describes the effects of adding organic montmorillonite clays (MMT) with different polarities (one polar and one non-polar) in recycled poly (ethylene terephthalate) (PET) and polypropylene (PP) blends. Styrene-Ethylene/Butylene-Styrene-maleic anhydride-graft (SEBS-g-MA) was used as a compatibilizer. MMT polarity was chosen based on the expected specific interaction of each clay with PET and PP. Samples were evaluated by wide angle X-ray diffraction, scanning electronic microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, dynamic mechanical analysis and mechanical tests. The clays caused no statistical change in the mechanical properties high-concentration PET blends, but increased Young’s modulus and decreased the elongation at break, tensile strength and impact strength of high-concentration PP blends. The different interactions between PET and SEBS-g-MA and the level of MMT exfoliation in each polymer-rich phase explained the results.

Resumo em Inglês:

Abstract In this work, the influence of Specific Mechanical Energy (SME) to disperse a trimodal distribution of carbon black (CB) by extrusion was studied to evaluating the effect on LDPE films properties (colorimetric and rheological). Three types of CB were previously evaluated (PART1) and determined that the best formulation was the combination between small (S) and medium (M) particles (F18 and F13), obtaining greater tinting strength with lower viscosity. In this work (PART2), these formulations were processed with different SME levels by varying the extrusion parameters, like screw rotation speed (N) and feed rate (Q), modulate the SME. The result of each process was evaluated by Tinting Strength, MFI, Total Transmittance and it was determined that the process with 600 rpm and 10 kg/h feed rate, generating a SME of 0.29 kWh/kg for F18-P03, developed the best results, mainly in the Tinting Strength, from 126.7% to 133.2% related to F18 (PART1).

Resumo em Inglês:

Abstract Poly(hydroxybutyrate-co-hydroxyvalerate) – PHBV plays an important role in sustainability and food safety. In this work, active packaging with antimicrobial properties was analyzed for the controlled release of active compound in three environments (acidic aqueous foods, fresh foods, and fatty foods). The compositions were produced with the addition of sepiolite nanoparticles (Sep) and oregano essential oil (OEO). The GC-MS analysis detected the presence of 3-methyl-4-isopropyl phenol as the primary constituent of the OEO (71.7%). The characterization of the films by FTIR and SEM confirmed the presence of additives, and the quantification of OEO and thermal stability of the nanocomposites was verified by TGA. Four kinetic models were used to analyze the release profile. Our findings indicate that it is possible to adjust the kinetic release of the OEO by varying the composition of the films, which is a promising alternative for producing an antibacterial biomaterial for application in food packaging.

Resumo em Inglês:

Abstract PMMA is one of the most used polymers for optical applications, due to its well-known optical properties and low-cost. PMMA/fumed silica nanocomposites were synthesized by in situ polymerization under sonication to produce optical materials using two types of silica, a PDMS surface-modified and an unmodified one. Silica content and sonication amplitude effects on nanocomposites properties were studied by factorial experimental designs. Nanocomposites retained the high transparency of pristine PMMA, especially at lower levels of silica and sonication. Rheological analysis indicated better dispersion of the unmodified silica in PMMA. Dispersed silica in the PMMA nanocomposites decreased the PMMA refractive index by 0.012, making PMMA/fumed silica suitable for the cladding layer of PMMA-core waveguides, resulting in the total reflectance phenomenon for light guiding. Therefore, PMMA/fumed silica nanocomposites provide promising materials for polymer optical devices, such as optical fibers and panels, optical sensors and biosensors, photonic platforms, daylighting, and multi-touchscreen displays.

Resumo em Inglês:

Abstract This study evaluates the influence of processing parameters and reactive extrusion on the mechanical and thermal behavior of PLA/PBAT (70/30, wt.%) blends. The effect of reverse mixing elements (RME) and feed rate (FR) of the extruder were studied using a factorial design of experiments. Further, two types of blends were processed by extrusion molding: with (AD) and without (NAD) additives. The FTIR analysis showed that PLA suffered some degree of degradation, being this process more pronounced for NAD blends. A better interaction between the PLA and PBAT phases occurred for reactive extrusion, inducing an improvement in the impact properties and thermal behavior. The cold crystallization temperature of the NAD blends decreased when two RME was used. Both RME and FR parameters affected the elastic modulus of NAD blends, while only FR affected the elastic modulus of AD blends.

Resumo em Inglês:

Abstract Firstly, this work shows the crosslinking of the Polyurethane/Single Wall Carbon Nanotube/ Polymethyl Methacrylate (PU/SWCNT/PMMA) nanocomposite at 298.15K using the PM3 semi-empirical method (Parameterized Model number 3), where the reaction was spontaneous and endothermic. The log P indicated a hydrophobic character. Subsequently, the Monte Carlo simulation was carried out at 303.15, 313.15 and 323.15K, where the Gibbs free energy and the dipole moment increased. However, the reactions were spontaneous and endothermic. The log P had hydrophobic character. Additionally, the entropy decreased due to the increase in intermolecular forces in the nanocomposite. Furthermore, FTIR analysis had similar vibrational frequencies, which was verified with the electronic distribution. Thus, this nanocomposite would have excellent physical and thermal stability, and it does not have reactions to polar solvents such as water so that it could be used in the human body.

Resumo em Inglês:

Abstract Sulfiting agents are added to crustaceans products to prolong their shelf life. However, depending on the concentration, these agents can be toxic to consumers due to the presence of SO2. In this context, a colorimetric indicator label based on starch and iodine was developed to detect SO2 in shrimp, showing whether the product is safe or not for consumers. The incorporation of iodine into the starch matrix resulted in labels with a smooth and homogeneous surface, and reduced water solubility from 9.26% to around 0.12%. In both in vitro and shrimp paste test, a visual detection response was observed in the label containing 0.02% of iodine when evaluated in the presence of 100 to 160 ppm of SO2, with ΔE* values greater than 5 (can be identifiable by the human eye). Therefore, the elaborated label showed potential as an economical and simple method to detect SO2 concentration in shrimp-based foods.

Resumo em Inglês:

Abstract In this study we evaluated the use of eucalyptus lignin as a stabilizer in combination with other stabilizers in a vulcanized elastomeric based on natural rubber. The stabilizers tested were 6PPD (N-1,3-dimethyl-butyl-N'-phenyl-p-phenylenediamine), TMQ (oligomerized 2,2,4-trimethylquinoline), paraffin wax and eucalyptus lignin. At predetermined time intervals, samples were taken from aging conditions and the mechanical properties and additive content were determined. The sample with a combination of wax and lignin in the same formulation showed the greatest resistance to oxidative degradation. In samples with only one stabilizer, the migration test indicated greater diffusion of lignin to the surface. Samples exposed to thermo-oxidative aging showed greater loss in the mechanical properties of tear strength and 6PPD consumption. In the accelerated aging with ozone, all showed a behavior more resistant to aging. We concluded that lignin can be used as a substitute for synthetic stabilizers, without impairing the performance of natural rubber compounds.

Resumo em Inglês:

Abstract In this paper, we report the synthesis and evaluation of a poly(vinyl alcohol)/poly(glycerol) dendrimer hydrogel incorporated with green synthesized silver nanoparticles (PVA/PGLD-AgNPs) using Cinnamomum verum extract as the reducting agent (Cz-extract). The Cz-extract was prepared using ultrasonic technique. UV-visible (UV-vis) spectra of Cz-extract confirmed the presence of cinnamaldehyde. PVA/PGLD-AgNPs films were prepared using 5, 10 and 20 mL of Cz-extract and characterized by UV-vis, Fourier transform infrared spectroscopy, Thermogravimetric analysis and X-ray diffraction (XRD). The surface plasmon resonance band in the UV-vis spectra confirmed the formation of AgNPs. XRD pattern confirmed the presence of silver, with average crystallite sizes calculated by Scherrer equal to 13.64 nm, 16.63nm and 20.27 nm for AgNPs prepared with 5 mL, 10 mL and 20 mL of Cz-extract, respectively. AgNPs release kinetic was studied by Korsmeyer- Peppas model. The antimicrobial results revealed that the PVA/PGLD-AgNPs hydrogels showed good antibacterial activity behavior against Escherichia coli.