Resumo em Inglês:

Abstract Heat-moisture treatment is type of physical modification that which cause changes in the technological characteristics of the starch. One of the sources of starch that presents potential of use of this treatment is sweet potato of the variety 'Rainha' (Ipomoea batatas). Therefore, the objective of this work was extract the sweet potato starch, apply the heat-moisture treatment in different relative humidity conditions (15, 20, and 25%), and characterize the starches as to water absorption capacity, morphology and crystallinity. Starch extracted from sweet potato resulted in a product of high purity. All modified starches showed a higher water absorption capacity when compared to native starch. The morphology of the starch granules remained unchanged after the modification and the same was observed with respect to the crystallinity. However, modified 15% moisture starch showed significant changes in the amylose content, water absorption, and crystallinity, these characteristics extend the use of this starch, for use in foods.

Resumo em Inglês:

Abstract The feasibility of using common chemicals to separate plastics from waste electrical and electronic equipment (WEEE) by froth flotation is investigated. Plastic waste is one of the WEEE polluters and a separation is necessary to recycle it. The most common plastics in electronic industries are acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS). These plastics are difficult to separate due to the similar specific weights and to both being repellent to water. Froth flotation allows for separating particles by the differences in their surface characteristics by selective wetting agents. The common chemicals are ethanol and acetic acid to depress the plastics. The process with 20% weight of ethanol was able to produce a recovery concentrate of HIPS with 98% and ABS with 96%. The process with 40% weight of acetic acid produces a recovery concentrate of HIPS with 96% and ABS with 83%.

Resumo em Inglês:

Abstract Off-site measurements of the dimensions of extruder screws are used to monitor their wear. This wear causes the presence of metals in the processed polymer. We detected the presence of iron in polymers processed with corrosive contaminants or abrasive fillers. To this end we processed poly(ethylene terephthalate), PET, pure or contaminated with poly(vinyl chloride), PVC, and other thermoplastics reinforced with glass fibers, talc or vegetal fibers, and analyzed the metals in the processed materials by X-ray fluorescence spectroscopy. We show that iron dispersed in the polymer melt is generated by corrosion from the PET contaminated with PVC and by erosion from abrasive fillers. The contents of iron in the extruded polymers clearly indicate equipment wear. This contaminant acts as a polymer pro-degradant, decreasing its lifetime. Additionally, we show that the lower concentration of iron for composites with vegetal fibers indicates a lower abrasion in comparison to talc and glass fibers.

Resumo em Inglês:

Abstract The use of araucaria pine nut shell in polymer composites may increase the pine nut value and help protec araucaria (Araucaria angustifolia) itself, which is an endangered species. The aim of this work is to study the influence of the size of pine nut shell fiber on the mechanical properties of composites made of this shell and polyurethane derived from castor oil. Composites with different polyurethane contents were manufactured with dried untreated pine nut shell sieved through 30 and 50 mesh sieves (0.6 and 0.3 mm, respectively). Composites were shaped by mechanical mixing of the components followed by hot pressing. Properties such as density, water absorption, and flexural strength were measured. Specimens were also characterized by SEM, FTIR, and TGA. The flexural strength of PU/0.3mm pine nut shell composites with 30% PU (wt%) was 57.7 MPa, and their water absorption was 7.37% after 24 hours of immersion.

Resumo em Inglês:

Abstract In this work, blends based on environmentally friend polymers such as Biopolyethylene (Bio-PE), Polycaprolactone (PCL) and Polyethylene graft maleic anhydride (PEgMA) added as compatibilizer agent were produced by conventional extrusion, aiming to produce bio-blends with synergic properties at low processing cost, being at same time non-polluting and therefore contributing to the environment preservation. Differential scanning calorimetry (DSC) showed that blending does not significantly interfere on the melting and crystallization behaviors of neat polymers, suggesting being low miscibility compounds. Mechanical properties were observed changing with blend composition as the impact strength significantly increased reaching values higher than 130% when compared to neat Bio-PE. Scanning electron microscopy (SEM) images showed honeycomb morphology in Bio-PE/PCL blends, and the addition of PEgMA decreased the coalescence contributing to obtain more stable and synergic compounds. Bio-PE/PCL/PEgMA at 80/20/10 contents presented the best properties and may be used for packaging materials (food containers, film wrapping), and hygiene products.

Resumo em Inglês:

Abstract Methacrylamides monomers for dental applications were synthesized using a one-step procedure starting from methacrylic anhydride and the respective diamine: N,N’-(propane-1,3-diyl)-bis(N-ethyl-2-methylacrylamide) (1), N,N’-(butane-1,4-diyl)-bis(2-methacrylamide) (2), N,N’-(octane-1,8-diyl-)bis(2-methylacrylamide) (3) and N,N’-(1,4-phenylene)-bis(2-methylacrylamide) (4). The structures were confirmed by 1H NMR, 13C NMR, FTIR-ATR and UHPLC-QTOF-MS. Thermal polymerization kinetics was investigated by modulated DSC for monomers (2), (3) and (4) using heating rates of 1, 2, 3 and 5 °C min-1. All IR spectra showed the C=C axial deformation at 1610 cm-1, in 1H NMR spectra the olefinic hydrogens were observed at 5.3 an 5.8 ppm and in 13C NMR, the vinylic carbons at 120 and 140 ppm. The exact m/z values were: 267.2068, 225.1595, 281.2222 and 245.1283 for monomers (1), (2), (3) and (4), respectively. The activation energy was: -182.7; -165.8 and -156.7 kJ mol-1 for monomers (2), (3) and (4), respectively. Monomers are promising candidates for use as hydrolytic stable adhesive systems for dental applications.

Resumo em Inglês:

Abstract Aromatic polyamides have properties of industrial relevance. However, the industrial and technological advancement has followed the trend of sustainability by seeking renewable source materials. In this work, polyamides were synthetized using 2,5-furandicarboxylic acid with p-phenylene diamine, triphenyl phosphite and two solvents (NMP and DMAc). To evaluate the influence of solvents on the reaction, a kinetic study of degradation was carried out by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and viscometric analysis. The viscosity value was in the range 70-80 mL/g. The TGA showed a higher thermal stability and activation energy for sample prepared with DMAc than the NMP. The XRD analysis showed that the PAFDMAc presents more defined crystalline forms due to its higher solvation capability. The crystalline form can be correlated with the differences of Ea, because the crystalline orientation and the number of hydrogens bonds in sample PAFNMP may be lower than the structure attributed to PAFDMAc.

Resumo em Inglês:

Abstract The aim of the present work was the obtaining and characterization of dental hybrid composites using nanoparticles (clay or silica) and boron-aluminum-silicate microparticles. We evaluated the dispersion of the nanofillers when changing their loading among 2.5%, 5%, 10% and 25% wt. Were tested, in the above quantities, four different types of nanofillers, two nanosilicas and two nanoclays The remainder of the inorganic phase, up to a total loading of 75% wt, was given by the boron-aluminum-silicate microparticles. The systems were characterized by XRD, TGA, LF-NMR, and . FTIR was used to determine the degree of conversion. The XRD and LF-NMR showed that the composites with 2.5% of clays, contained an exfoliated profile, and the groups with higher amounts of clay showed intercalated areas or the agglomeration of these particles. Furthermore, the silicas were agglomerated in all groups. The thermal resistance of the material was not affected by the silicas, but improved when using 2.5% of nanoclays. On the other hand, the addition of these particles caused the reduction of the degree of conversion of the systems.

Resumo em Inglês:

Abstract Magnetized polymers are produced by incorporating magnetic particles in a polymeric matrix. This article describes the use of the suspension polymerization technique using ethyl acrylate and divinylbenzene as monomers, in the presence of heptane and/or toluene as diluent, initiated by free radicals. To produce the polymer, we first performed fractional factorial planning to help visualize the factors that could influence the results, to verify the action of different responses simultaneously. Five factors were evaluated that influence the production of the polymer and incorporation of iron in the matrix. Infrared spectroscopy, X-ray fluorescence, magnetic force testing and scanning electron microscopy were used to characterize the samples. The results indicated the positive influence of the quantity of the polymerization initiator on the yield of the process and the negative effect of the content of divinylbenzene on the incorporation of iron in the matrix and on the magnetic force.

Resumo em Inglês:

Abstract Bone fractures to be corrected need stabilization of their extremities, which is achieved with the use of plates and screws. This research aimed to produce castor bean polyurethane (Ricinus communis), to make resorbable plate, structural and thermal analysis. The production was made by the glycerolysis of the triglycerides present in the oil, after addition of polyol/glycerol and hexamethylene diisocyanate (HDI) to form urethane structures, with and without addition of hydroxyapatite. The characterization was by FTIR spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry and thermogravimetry. Plates with dimensions of 40 mm X 10 mm X 2 mm were obtained. The SEM showed flat and homogeneous surface. DRX analysis showed the semi-crystallinity of the biomaterial. Glass transition and thermal stability up to 50 °C were observed, followed by thermal decomposition up to 450 °C. The produced polyurethane showed it is possible to be applied in the manufacture of plate.

Resumo em Inglês:

Abstract High performance polymeric materials such as poly-ether-ether-ketone (PEEK) are increasingly being used for challenging tribological applications in order to replace metal parts in vehicle engines and transmissions. The tribology of natural PEEK, under oil-lubricated conditions, was studied for different metal counterbody finishes. Two different finishing processes were selected for this study: turning and polishing. The test system used was a tri-pin on disc, with pins made of PEEK and counterbodies made of steel, and then dipped in ATF Dexron VI oil. The conclusion was that the wear rate generated by turning was about seven times as high as the wear rate generated by polishing. The friction coefficient displayed a direct correlation with the lubrication regime, and the level of counterbody roughness. On average, the friction coefficient on the hydrodynamic regime for polishing was more than 3 times lower than the friction coefficient in the boundary regime for turning.

Resumo em Inglês:

Abstract The present paper discusses the aspects of synthesizing palladium (Pd) doped (Pd+2 and Pd0) poly(vinyl chloride) (PVC) using simple solution cast technique. The Pd loading to PVC was altered from 2.5% to 10.0% and the material properties were studied using UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and Field Emission Scanning Electron Microscopy (FE-SEM). Thermal behavior of all the samples were studied using thermogravimetric analysis (TGA) and Broido’s method was employed to analyse the kinetic parameters involved in different degradation steps. All the composite films were sandwitched between disk shape gold electrodes; electrical contacts were established to study the dielectric properties. The influence of Pd loading on the dielectric properties of PVC were examined. Finally, the catalytic properties of Pd0 composites were studied using standard model reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of aqueous sodium borohydride and reported.

Resumo em Inglês:

Abstract Poly(ε-caprolactone)-block-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, triblock) and Poly(ε-caprolactone)-block-(poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide)-poly (ε-caprolactone) (PCL-PEO-PPO-PEO-PCL, pentablock) copolymers were synthesized by transesterification with reduction of PCL molecular mass, enabling fewer reactions, lower temperatures, and eliminating extensive purification steps. Free hydrophilic groups were removed from the samples by selective precipitation, and 1H-NMR, FTIR, GPC and DSC analyses characterized the structure and properties of the resulting copolymers. The detection of remaining hydrophilic groups indicates the formation of the amphiphilic block copolymers (BCPs). Further, we obtained polymeric nanoparticles with monodisperse size distribution profiles by nano-precipitation from both the triblock and the pentablock copolymers using a microfluidic device, resulting 144.6 and 188.9 nm size and 0.093 and 0.102 nm polydispersity index, respectively. The nanoparticle assembly depends on the copolymer composition, and the possibility of nanoparticle assembly corroborates to the block structure of the copolymers, and the success of this synthesis route to obtain BCPs.

Resumo em Inglês:

Abstract Graphene is a new carbon based nonmaterial that attracts the technology and constitutes one of the great promises for nanotechnology applications in a near feature. It’s having versatile intrinsic mechanical, thermal and electrical properties.By Incorporation of small amount of graphene fillers into polymer matrix can create attractive bio composites with different morphological and functional properties. The development of biomaterials with special properties is a requirement in biomedical research, particularly in biomedical application. The aim of this work was to develop biocompatible, usable bio composites for biomedical applications using graphene as filler. Recent research evidenced that grapheme-polymer bio composites are promising materials with applications ranging from transportation, biomedical systems, sensors, electrodes for solar panels and EMI.Chemically converted graphene (CCG) solution were prepared through reduction of GO, and Polycaprolactone (PCl), a synthetic biodegradable and biocompatible aliphatic polyester also a suitable for developing biocomposites.

Resumo em Inglês:

Abstract Presently, there are significant research efforts being undertaken to produce bio-based chemicals in a cost-effective way. The polymer chemists and engineers are no exception to this. Additives for polymers correspond to a large section of the plastics market and bio-based products can substitute many of them. The scientific literature has a large number of publications focusing on the preparation and testing of bio-based polymer additives; however, the small number of products that reach the market, which are bio-based, does not reflect this. In terms of the global market, the environmentally friendly appeal of bio-based additives alone is not sufficient; the bio-based product must have similar or better performance than the oil-based and be comparable or lower in cost than the existing products. In this review, we focus on bio-based polymer additives that have already reached the market or have a real possibility of reaching the market in a cost-effective way.