Resumo em Inglês:

Abstract The aim of this research was to separate a mixture of six post-consumer plastics (PS, PMMA, PVC-D, PVC-M, PET-D and PET-S) by combination of sink-float separation and froth flotation.. In sink-float method two mediums of separation were used: sodium chloride water solution and ammonium nitrate water solution. Sink-float method allowed complete separation of the less dense plastic (PS) from intermediate density plastics (PMMA and PVC-D) and from high density plastics (PET-S, PET-D and PVC-M); also allowed good separation of intermediate density plastics (PMMA and PVC-D) from high density plastics (PVC-M, PET-D and PET-S) with an efficiency close to 100%. Separation of PVC-M from PET-D and PET-S by sink-float method led to fair results allowing a separation efficiency of about 60%. Since PMMA and PVC-D have similar density, their separation was achieved by froth flotation, using sodium lignosulfonate as selective wetting agent of PVC-D, with a separation efficiency of 85%.

Resumo em Inglês:

Abstract This work aimed to obtain and analyze composite materials made from green polyethylene and calcium carbonate extracted from chicken eggshells. The shells were collected and prepared for later extraction of calcium carbonate. With the X-ray diffraction analysis it was possible to confirm that both the in natura reinforcement and the calcined one, have the same polymorph mineral (calcite). With regard to thermal behavior, compounds with in natura reinforcement showed greater mass loss due to the moisture contained in them. The results showed a significant increase in Young’s moduli of the composites compared to the pure polymer. The scanning electron microscopy showed good dispersion and adhesion between the reinforcement materials and matrix. In view of the results, eggshells have the potential to be used as fillers, where greater rigidity is required. Since these materials come from a waste material, with low cost, their use becomes even more viable.

Resumo em Inglês:

Abstract Biomaterials developed with biopolymers contribute to the healing process of healthy or diabetic patients. The objective of the present study was to evaluate the effect of honey incorporation (0.3, 0.6, and 1.2 g/100 mL) in chitosan/collagen/glycerol composite films. The Ch/Coll/1.2H films revealed the greatest percentage of elongation (27.10%) and Young´s modulus (65.58 MPa). The barrier properties (WVTR and WVP) exhibited a significant increase when the honey was incorporated into the films. The absorption capacity, solubility, and enzymatic biodegradability were lower in films containing honey. The chemical interactions between the functional groups of the films were verified by FTIR. The morphology studied by SEM confirmed the mixture’s homogeneity. Finally, all formulations exhibited antibacterial properties against Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, and Salmonella Typhimurium. The aforementioned properties of formulated dressings are suitable for their potential application in chronic wounds.

Resumo em Inglês:

Abstract In this research, oven-dry density, air-dry density, and water absorption levels of Oriental beech treated with flame-resistant chemicals (FRC) and coated with polyurethane/polyure (PU) and epoxy (EP) were evaluated. According to ISO 3129 standard, the experimental specimens were made from Oriental beech wood. Wood specimens were subjected to 3% aqueous solutions of boric acid, borax, a boric acid and borax mixture (1:1; weight: weight), ammonium sulphate, and polyurethane/polyurethane, and epoxy resins before being coated with these substances. Results showed that oven-dry and air-density values of PU coated wood were much higher than EP coated wood. Water absorption (WA) levels of PU coated of wood were lower than EP coated wood. While FRC treated and PU coated wood resulted in lower WA levels than only PU coated wood, FRC treated and EP coated wood resulted in higher WA levels than only EP coated wood.

Resumo em Inglês:

Abstract This work aimed to incorporate thyme essential oil into films composed of pectin to provide antimicrobial action to them. The effect of adding essential oil on the films' mechanical, physical-chemical, and barrier properties and their degradability was evaluated. Essential oil addition was possible by using Tween® 20 as an emulsifier, and it was possible to observe antimicrobial activity in the films containing 1.0 wt.% and 2.0 wt.% essential oil. The films containing thyme essential oil were more elastic and thicker but less resistant, with high permeability to water vapor and more hydrophilic relative to other formulations. Scanning electron microscopy analysis showed the presence of heterogeneities in the formulations with essential oil. The films produced using the optimized formulation (30 wt.% glycerol, 1.0 wt.% thyme essential oil, and 0.5 wt.% Tween® 20 relative to pectin mass) degraded entirely after 24 days of exposure to standard soil.

Resumo em Inglês:

Abstract Prolonged exposure to environmental conditions such as ultraviolet radiation, humidity, and temperature, to which carbon fiber-reinforced thermoplastic polymer components are exposed during their service life, can lead to significant changes in mechanical, physical, and chemicals properties, and can often be irreversible, resulting in premature component failure. This study presents the influence of accelerated weathering exposure times (400 h, 800 h, and 1200 h) on the mechanical, thermal, and structural properties of carbon fiber (CF)/polyamide 6 (PA6) laminates. Analyses of composite surfaces were carried out using microscopy and contact angle measurements, which indicated that the factors of exposure to accelerated only affected the surface of the composites, showing signs of the beginning of degradation. The tensile strength (609 MPa ± 10 MPa) and interlaminar shear strength (27 MPa ± 0.9 MPa) did not present significant changes, showing that the reinforcement, the matrix, and the interface remained stable after exposure to accelerated.

Resumo em Inglês:

Abstract The traditional method of fixing cracked pipes by welding needs stopping the production. In this study, a composite material is used to repair pipelines without interrupting production, saving both time and money. Hand Layup and vacuum infusion techniques were used to prepare glass strand mat and intra-ply hybrid glass - carbon fibers composites repairs. To show the composites' strength, blister, double cantilever beam, and peel tests were conducted. A novel modified blister test was utilized to show effectiveness of laboratory tests on real pipeline. The results indicate that vacuum infused intra-ply hybrid composite exhibited the highest strength. The experimental results of the best composite were compared with the finite element model under blister test, and the results were found to be identical. The modified blister test on the real pipe provides a better indication about the good strength of the composite repair compared to previous researches.

Resumo em Inglês:

Abstract Bacterial nanocellulose (BNC) membranes have interconnected porous nanostructures and excellent biocompatibility. Functionalizing these with calcium phosphate sources and metal ions confers optimized properties to the biomaterial. This study aims to synthesize BNC membranes, functionalize them with copper and magnesium apatites, characterize and evaluate their cytotoxicity and antimicrobial potential. Membranes were synthesized for 8 days in Mannitol Medium. The biocomposite production was by immersion cycles. The biocomposites were characterized by porosity and swelling capacity, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), antimicrobial properties and cytotoxicity assays. The FTIR and SEM results showed that phosphate groups were incorporated into the BNC. The TGA analysis also indicated the incorporation of the inorganic phase. The membrane functionalization with Cu promoted the antimicrobial properties of the biomaterial. However, functionalization with Mg had a more positive behavior on cell viability, proving to be more suitable for use as an implantable material.

Resumo em Inglês:

Abstract In this study, the utilization of neem gum powder and snake grass fiber, gathered from snake grass plants is discussed. The fibers are produced in various volume percentages of 5, 10, 15, 20, 25, 30 and 35% and their mechanical characteristics such as tensile strength, flexural strength, impact strength, and critical stress intensity are investigated. The combination of 30% snake grass fiber, 15% neem gum powder and 55% epoxy resin, in terms of volume, contributes towards the attaining of better mechanical properties. The tensile strength, flexural strength, impact strength, and critical stress intensity of this blend are respectively 36.497±0.429 MPa, 65.87±1.85 MPa, 2682.67±1.866 J/m2 and 42.291±2.61 Pa mm-1/2. The mechanical properties improve with the addition of the fiber. However, as more fiber is added, the adhesion at the interface gets reduced. The automotive and aerospace sectors can use this composite material, which enhances the mechanical characteristics for interior applications.

Resumo em Inglês:

Abstract Graphene oxide (GO) was electropolymerized with polyaniline (PANI) during graphite exfoliation in 0.1 M H2SO4 electrolyte and 0.1 M aniline monomer solution. Characterization techniques, including Infrared Absorption Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), UV-vis spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and cyclic voltammetry, were utilized. XRD analysis confirmed GO multilayer exfoliation from the graphite anode, while UV-vis and FTIR techniques confirmed PANI electropolymerization. SEM images revealed PANI distributed between GO multilayers with a nanoneedle morphology. Cyclic voltammetry in 1 M H2SO4 demonstrated that the GO/PANI composite achieved a specific capacitance of 117.440 Fg-1, in contrast to GO's 1.243 Fg-1, both at a scan rate of 1 mVs-1. This enhancement is attributed to the improved electrical conductivity from PANI and graphene oxide. These results highlight the potential of the GO/PANI composite for high-performance supercapacitors and energy storage systems.

Resumo em Inglês:

Abstract This work studied the incorporation of organic acids as crosslinking agents and reaction time on the properties of poly(alcohol vinyl) (PVOH) hydrogels to act as scaffold systems to compounds incorporated into agriculture systems. PVOH hydrogels crosslinked with citric and L-malic acids were prepared, and the effects of heat-treatment time, and temperature on their swelling and hygroscopic performances were investigated by FTIR, thermal analysis and swelling. Both the swelling and rate of water uptake of hydrogels decreased with increasing heat-treatment time. While the swelling decreased with heat-treatment time, the chemical crosslinking shown in FTIR increased. DSC results indicated adsorbed water in the uncrosslinked PVOH and hydrogels, and the absorbed water changed the melting point and glass transition temperature. TGA analysis showed that the incorporation of organic acids brought thermal stability. The results obtained show effective crosslinking hydrogels by L-malic acids and possibilities to use in scaffold systems and controlled release.

Resumo em Inglês:

Abstract A variety of fiber-reinforced polymer (FRP) has been described in literature, with a considerable subset of studies focused on fiber surface treatment (sizing), performance enhancement of matrix and fibers both synthetic and natural, and development of more ecologically sustainable composites. The present review discusses the different types of fibers and matrices and their applications, depending on the chemical and mechanical properties of their composites. In order to evaluate the performance of FRP composites and explore the characteristics of the involved materials, some analytical techniques are considered paramount, such as thermal analysis, microscopy, Fourier transform-infrared spectroscopy (FT-IR), and others. On this basis, this review addresses the state-of-the-art of material characterization methodologies, provides a comprehensive overview of different types of FRP found in literature, as well as links the analytical techniques with the main applications contributing to future studies and research in this area.