Abstract in English:Abstract Polymer compatibilizer agents are crucial for industrial materials development. Compatibilizer agents may be prepared by melt-grafting in the reactive extrusion process which is cheaper and environmentally friendly. Maleic anhydride-grafted acrylonitrile-butadiene-styrene (ABS-g-MA) has emerged as a relevant compatibilizer agent for immiscible blends, like polycarbonate (PC)/ABS. In this work, ABS-g-MA was prepared by a simple reactive extrusion process using ABS, maleic anhydride (MA) and benzoyl peroxide (BPO). The MA:BPO ratios of 1:0.5 and 1:1 varying the content of MA by 1, 2 and 5 wt% were investigated. The grafting reaction was confirmed through Fourier transform infrared spectroscopy (FT-IR), grafted degree (GD%), thermal and rheological analysis. The effectiveness of the compatibilizer agent was evaluated in PC/ABS blends (70/30 and 85/15 blend ratios). The addition of 5 wt% of ABS-g-MA (5 MA:2.5 BPO) in the PC/ABS blends promoted an expressive reduction of ABS domain sizes and better dispersion in the PC matrix.
Abstract in English:Abstract The aim of this work was to investigate the effects of mercerization on the structure of castor oil cake (CC) and on the tensile properties of LDPE/PHB/CC composites. To achieve this goal, the fibers were treated with NaOH solutions (5 and 10 wt%). Characterization techniques such as: scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the structure of modified fibers. The composites were processed in a Haake mixer. Tensile tests of the composites were performed according to ASTM D638 standard. The analyzes revealed that mercerization promoted a partial conversion of cellulose I into cellulose II. Mercerization performed with 5% NaOH solution improved the tensile properties of the LDPE/PHB/CC composites, which were superior to those obtained with the 10% NaOH solution. This result suggests that the higher concentration of NaOH compromises the integrity of the fibers, deteriorating the mechanical properties.
Abstract in English:Abstract The blending of nanoclay in polymers has potential prospects in the recent development of composite technology. In this present research work, Nanoclay was added to Glass fiber and Abaca fiber reinforced hybrid epoxy composites to enhance the wear resistance of the material. Nanoclay at weight ratios of 2%, 4%, 6%, and 8% was reinforced and the composite was fabricated into laminates using compression moulding. Nanoclay reinforced composites were tested for mechanical characteristics and wear rate in comparison to the non nanoclay reinforced hybrid composites. Water absorption character and morphology were also studied. It was observed that the 4% nanoclay reinforced composites showed the optimum results, with an increase in tensile strength, flexural strength and impact strengths of 6.6%, 19.6%, and 22.6% respectively when compared with EGA composite. Similarly the wear rate of the 4% nanoclay reinforced composite also was better than the EGA composite, showing an increase of 22.1% improved resistance.
Abstract in English:Abstract In this work, nanocomposites based on the triblock copolymer polystyrene-b-polyisoprene-b-polystyrene (SIS) thermoplastic elastomer filled with multiwall carbon nanotubes (MWCNT) were obtained by melt mixing. The nanocomposites were characterized by oscillatory rheometry, electrical resistivity, small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM). The results showed that both, rheological and electrical percolation were achieved at MWCNT loadings between 1-3 vol.%. Rheological tests revealed that the insertion of MWCNT into SIS significantly enhanced the process of relaxation of SIS blocks. Resistivity measurements revealed that conductive nanocomposites were obtained at MWCNT loadings ~1.6 vol.%. The electrical resistivity decreased eleven orders of magnitude from neat SIS to SIS/ 5 vol.% MWCNT. Finally, SAXS and TEM showed that the melt mixing process and the presence of MWCNT hampered the self-assembly of SIS into well-ordered domains.
Abstract in English:Abstract In this work, banana fiber was used as reinforcement for the preparation of a thermoplastic elastomer composite (TPE). Few studies are exploring the natural fiber incorporation on TPEs, with no one using banana fiber. The fiber was extracted from banana pseudostem and modified with an alkaline solution. The untreated and treated banana fibers were incorporated in 2%, 5%, and 10% in SEBS. The mixture was performed in a thermokinetic mixer (K-Mixer) and plates prepared by compression molding. The composites were characterized by Scanning Electron Microscopic (SEM), tensile testing, mechanical dynamical analysis (DMA). It can be observed that the samples with untreated fibers presented a higher tensile strength, except for the incorporation of 5% of BF. Young's modulus increase as the fiber's incorporation grows, indicating greater rigidity of the composite. It was found that the chemically treated banana fiber composites, e.g., TPE/TBF5 and TPE/TBF10, shows a 15.4% and 22.2% higher elongation.
Abstract in English:Abstract Previous studies have proven that the flour obtained from the residue of Jabuticaba (Jab) juice and wine industries is source of bioactive compounds and an option for the production of food such as extrudates. The objective of this work was to produce extrudates with different concentrations (0, 5, 10, 15, 20%) of non-fermented and fermented Jab pomace flour, as well as to evaluate their physical, chemical and technological properties and the effect of the extrusion process on the antioxidant capacity. Results showcased that the extrudates have low content of resistant starch (0.26 g/100 g) and extrusion conditions decreased the content of polyphenols and antioxidant potential. The addition of 20% non-fermented Jab pomace reached an antioxidant activity of 2904 µg trolox/g in the DPPH method, and promoted rheological changes in the product, such as lower expansion index, higher density and hardness; while presenting higher phenolic content and antioxidant capacity.
Abstract in English:Abstract Blends of zein and poly(vinyl alcohol) (PVAl) were processed in an internal mixer (150ºC, 50 rpm) for 5-8 minutes. Glycerol and oleic acid were used as plasticizers. The mixtures obtained were then compression molded and further characterized by Fourier transform infrared spectroscopy (FTIR), water-absorption experiments, mechanical tests, and scanning electron microscopy (SEM). FTIR analysis indicated the existence of hydrogen bonding interactions between zein and PVAl. Tensile tests showed that the addition of PVAl increased the flexibility of the blends. The tensile strength ranged from 1.7 to 5.7 MPa, elongation at break ranged from 2.7 to 32% and Young’s modulus ranged from 433 to 7371 MPa. Water absorption at equilibrium decreased with increasing zein content, which favored a brittle behavior in the zein/PVAl. The blends were immiscible in the composition studied and the presence of voids indicated poor interfacial interaction between the polymers.
Abstract in English:Abstract Nylon composites were developed using 5-20 wt.% of Talc, Kaolin, Mica and Calcium Carbonate (CaCO3) particulates. Mechanical and free vibration characteristics of nylon composites were examined through experimental and analytical approach. Particulate filled nylon composites exhibited enhancement in tensile strength, specific stiffness, natural frequency and damping factor compared to pure nylon. As a whole, talc reinforced nylon composites especially 15 wt.% filler content (T15) portrayed significant performance in mechanical and vibrational characteristics. This is followed by nylon composites based on kaolin (K15) and mica (M20) compared to CaCO3 based nylon composites. T15 depicted 18.13%, 33.33%, 81.2% increment in tensile strength, natural frequency and damping factor compared to pure nylon. The simulated ANSYS results are in agreement with experimental results. Among four different particulates, talc is proven as appropriate reinforcing agent for nylon owing to larger surface area of talc particles and polar-polar interaction between talc and nylon matrix.
Abstract in English:Abstract In this work we discuss the wettability, chemical composition, surface morphology and optical transmittance of polyvinyl chloride (PVC) samples treated by Plasma Immersion and by Plasma Immersion Ion Implantation. The total pressure of N2 or SF6 was 6.66 Pa, for treatments of 900 s, applied rf power of 25 and 100 W, and the substrate temperature was about 298 K. In PIII, high voltage pulses of -2400 V at a cycle time of 30 µs and a frequency of 300 Hz were used. The wettability of the samples was assessed via contact angle measurements, which indicated either hydrophilicity or hydrophobicity, depending on the plasma composition. X-ray Photoelectron Spectroscopic analysis confirmed strong fluorine attachment to the surface after treatments using SF6 plasmas, and the presence of oxygen after treatments using nitrogen plasmas. Atomic Force Microscopy images showed that the roughness Rrms, depends on the plasma conditions. Optical transmittance in the visible region, T (λ), was increased by plasma immersion. The greatest contact angle observed was 142º (PI cathode), while the highest roughness was 213.2 nm. The highest optical transmittance in the visible region was around to 90% (PI anode).
Abstract in English:Abstract The study investigates the gloss and color changes values of Calabrian pine (Pinus brutia Ten.) wood impregnated with some copper content impregnation chemicals such as Celcure C4, Korasit KS, and Tanalith E 8000 and then water-based varnish (WBV) and polyurethane varnish (PV) coated after 6 months of weathering. The results of study showed that gloss values of PV coated Calabrian pine wood were higher than that of WBV coated Calabrian pine wood before weathering. The gloss values of all treatment groups decreased after weathering. Lightness values of Calabrian pine wood also decreased for all treatment groups after weathering. Pre-impregnation before PV coating resulted in lower 𝜟L* values of Calabrian pine wood. While all treatment groups tended to turn reddish by giving 𝜟a* positive values, they tended to turn bluish by giving negative 𝜟b* values. The lowest total color change was obtained with only WBV coated Calabrian pine wood.
Abstract in English:Abstract The development of polypyrrole-based nanocomposites as alternative antibacterial agents represents a promising strategy to be applied against the prevailing multi-resistant bacteria. Herein, it is reported the most recent development of antibacterial materials based on the combination of polypyrrole and different fillers (metal nanoparticles, carbon nanotubes, and polysaccharides) and strategies to improve their action (such as light and electrical stimulus). The synergistic interaction of electrostatic forces provided by charged polypyrrole combined with the permeation of nanoparticles through the cell wall favors the leakage of cytoplasmic components and reinforces the antibacterial activity of the resulting material, observed in all-organic composites of polypyrrole and chitosan that reached superior performance against Escherichia coli (108 CFU) or metal-polymer composites (polypyrrole-palladium) with an outstanding performance against different types of bacteria. The development of binary and ternary composites is explored to potentialize the antibacterial synergy of components.
Abstract in English:Abstract In the last decade, bacterial cellulose (BC) has received considerable attention around the world, including in Brazil. The unique properties of BC, such as mechanical stability, tensile strength, thermostability, crystallinity, purity and biocompatibility make it a promising candidate for commercial applications in different areas. This article provides a comprehensive synthesis of commercial applications and studies related to BC around the world and shows the importance and development of Brazilian research during the last decade. In this review we present an overview of BC structure, biosynthesis and possible applications of BC mainly in the food, electronics, bioengineering, cosmetics and biomedical areas. The most significant contributions of Brazilian researchers using BC have been carried out in the biomedical area. Despite the increase in BC reserch, Brazil also needs to develop strategies to expand the use and commercialization of BC products, for which government financial support is extremely necessary.