Scielo RSS <![CDATA[Polímeros]]> vol. 27 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Polímeros, from now onwards published only in English…..]]> <![CDATA[Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends]]> Abstract In this work, low density polyethylene (LDPE)/plasticized starch (TPS) blends were prepared. The TPS employed in this study was obtained by plasticization of tapioca starch with a hyperbranched polyester polyol. Differential scanning calorimetry analysis showed that the melting temperature increased with the TPS content. The opposite effect was exhibited in the crystallization temperature and additional changes were not observed during the heating. X-ray diffraction analysis showed a reduction in intensity of the peak at Bragg’s angle 17.5°, proving a diminution on A type crystallinity with the increasing amount of LDPE. Micrographs obtained by scanning electron microscopy exhibited starch granules without destructure. TPS acted as a filler to LDPE, since the mechanical properties (Young’s modulus and tensile strength) improved ostensibly. The Young’ modulus and tensile strength decreased with the amount of LDPE, however, the elongation at break exhibited an opposite behavior. <![CDATA[Mechanical recycling of tags and labels residues using sugarcane bagasse ash]]> Abstract In this study, an alternative method for recycling residues of labels and stickers (parings) containing biaxically oriented polypropylene (BOPP) and polyurethane-based glue was discussed. The recycling of this type of material is complicated, once the separation and the milling processes are difficult to be accomplished, due to the presence of a large amount of glue. In this study, sugarcane bagasse ash was used to enable the milling process of stickers residues. Composites were prepared with post-consumer polypropylene extrusion with different polypropylene/parings ash ratio. These materials were analyzed by tensile, three point flexural, hardness, density, water absorption, Izod impact tests, thermogravimetric analysis, environmental exposure and scanning electron microscopy. Addition of sticker residues/ash to the polypropylene matrix makes the material more rigid and does not affect significantly thermal and degradation properties. Thus, the recycling process proposed in this paper is environmentally and economically viable. <![CDATA[Removal of Remazol brilliant violet textile dye by adsorption using rice hulls]]> Abstract The release of industrial effluents into the environment causes widespread contamination of aquatic systems. Adsorption is seen as one of the most promising treatment processes, and lignocellulosic materials have gained prominence as adsorbents. This study investigates the potential of rice hulls, either in natura or treated with nitric acid, as adsorbents for removal of the dye. The adsorbents were characterized by infrared spectroscopy, solid state 13C-NMR, thermogravimetric analysis, and pH at point of zero charge. The dye adsorption experiments were carried out in batch mode, using different experimental conditions. The kinetic adsorption data could be fitted using the model of Elovich. The Freundlich model provided the best fit to the isothermal data. The thermodynamic parameters confirmed the spontaneity of the adsorption process. These adsorbents offer an alternative for dye removal, with advantages including biomass availability and low cost. <![CDATA[The effect of gelatin amount on the properties of PLA/TPS/gelatin extruded sheets]]> Abstract Films and sheets composed by poly (lactic acid) (PLA)/thermoplastic starch (TPS) and TPS/gelatin blends have already been produced and characterized in the literature. However, materials produced with these three biopolymers have not been clearly investigated. In this work, extruded sheets were produced with PLA, TPS (glycerol as plasticizer) and different amounts of gelatin (0, 1, 3 and 5 wt%) in a pilot scale co-rotating twin-screw extruder coupled with a calender. The extruded sheets were characterized in regards to their water solubility, thickness, density, water vapor permeability (WVP), moisture sorption isotherms, mechanical properties and microstructure. The results showed an increase in solubility and WVP besides a decrease of about 30% in tensile strength, Young's modulus and elongation at break. Extruded sheets microstructure revealed smother surfaces and homogeneous morphology with the addition of gelatin. The experiments demonstrated that extrusion and calendering process is a viable way to produce PLA/TPS/gelatin sheets with interesting properties. <![CDATA[Use of pH-thermosensitive hydrogels for nickel ion removal and recovery]]> Abstract N-isopropylacrylamide / itaconic acid hydrogels were prepared in this study, varying the proportion of itaconic acid in the pregel mixture. The kinetics of the hydrogel swelling at 4 °C was determined, obtaining the kintetic patameters, in accordance with the second-order kinetic model. Similarly, the capacity to absorb water in terms of temperature was determined, along with the transition temperature of the samples. The influence of temperature on the capacity of the hidrogels to absorb nickel from aqueous solutions at 5% of NiCl2 and its subsequent recuperation was determined. <![CDATA[Effect of shrimp shells milling on the molar mass of chitosan]]> Abstract Shrimp shells are a raw material rich in chitin, a precursor of chitosan biopolymer. The variables of processing (demineralization, deproteination and deacetylation) can be manipulated to determine the main characteristics of chitosan, the degree of deacetylation (DD), and average molar mass. This study evaluated the influence of one of the unit operations of shrimp shell physical processing, the milling, on the final product characteristic, chitosan. After different milling conditions, the raw material was subjected to standard chemical processing for chitin extraction, followed by deacetylation to obtain chitosan, which is characterized by 1H NMR, SEM, XRD, N2 physisorption (BET) and viscometry. The results indicated that the milling time of the raw material can be manipulated to increase the material depolymerization, significantly influencing the molecular weight reduction of chitosan a desirable feature for many applications of this biopolymer, and usually obtained by complex chemical and enzymatic methods. <![CDATA[Characterization of low cost orally disintegrating film (ODF)]]> Abstract Orally disintegrating films (ODF) produced with a hydrophilic polymers are a thin and flexible material, wich disintegrate in contact with saliva and can vehicule bioactive materials. The aim of this study was to develop and characterize ODF formulation with potential to act as a carrier for different bioactives compounds prepared with low cost polymers. Gelatin (G), starch (S), carboxymethyl cellulose (CMC) and their blends (G:S, CMC:S, CMC:G, and CMC:S:G) were prepared by casting technique with sorbitol as a plasticizer. The formulations were characterized in terms of visual aspects, FTIR, SEM, mechanical characteristics, hygroscopicity, dissolution (in vitro and in vivo) and swelling index. FTIR analysis revealed that no interaction between polymers in ODF was observed. By SEM, it was possible to observe differences on surfaces by different polymers. ODF made with CMC and CMC:G presented higher water absorption (P&lt;0.05) and higher swelling index probably due to the higher water affinity by CMC. Formulations with G, CMC:G and CMC:S:G presented the highest values of tensile strength (P&lt;0.05). ODF prepared with S alone presented the highest disintegration time, the others formulations showed in vitro dissolution ranging from 5.22 to 8.50 min, while in vivo dissolution time ranged from 2.15 to 3.38 min. By the formulations made with G and blend of G:S and CMC:S:G it is possible to develop a ODF of low cost with desired characteristics being an alternative vehicle to deliver functional compounds for continuous use. <![CDATA[Rice husk ash as filler in tread compounds to improve rolling resistance]]> Abstract In the tire industry carbon black is being replaced by silica as a filler in recent due to the development of “green tires”. Amorphous precipitated silica in combination with a silane coupling agent as a filler in tread compounds can result in fuel savings of 3% to 4% compared to a tire having treads made from compounds with carbon black. This means a 20% reduction of the rolling resistance and consequently lower greenhouse gas emissions. On the other hand, rice is one of the most important food crops generating around 22% in weight of husk during its milling, a material that is mainly used as fuel for energy generation, resulting in ash. Rice husk ash (RHA) contains over 70% of silica in amorphous form. In this paper we evaluated the effect of replacing carbon black with RHA in a basic tread formulation. Compounds mechanical, dynamic properties and morphology were analyzed. <![CDATA[Characterization of biopolymers and soy protein isolate-high-methoxyl pectin complex]]> Abstract This study aimed at characterizing the soy protein isolate and high-methoxyl pectin biopolymers individually, and the complexes formed by both at different proportions and pHs in order to find the most suitable pH and biopolymer ratios to food application as stabilizers. The biopolymers were evaluated through solubility, charges, turbidimetry, and optical microscopy analyses; the systems with the pair of biopolymers were analyzed through turbidimetry and optical microscopy. High-methoxyl pectin showed high solubility at all pHs investigated. The soy protein isolate showed low solubility at pH 4.5, which is close to its isoelectric point, and complete solubility at pH 11.0. The formation of complexes suggested an attractive interaction between the biopolymers, with high absorbance reading values and images of complexes from optical microscopy. These complexes were present in systems with pHs below the soy protein isolate's isoelectric point, with positive charges; the high-methoxyl pectin, however, had negative ones. <![CDATA[A quantitative relationship between <em>T</em><sub>g</sub>s and chain segment structures of polystyrenes]]> Abstract The glass transition temperature (Tg) is a fundamental characteristic of an amorphous polymer. A quantitative structure-property relationship (QSPR) based on error back-propagation artificial neural network (ANN) was constructed to predict Tgs of 107 polystyrenes. Stepwise multiple linear regression (MLR) analysis was adopted to select an optimal subset of molecular descriptors. The chain segments (or motion units) of polymer backbones with 20 carbons in length (10 repeating units) were used to calculate these molecular descriptors reflecting polymer structures. The relative optimal conditions of ANN were obtained by adjusting various network paramters by trial-and-error. Compared to the model already published in the literature, the optimal ANN model with [4-7-1] network structure in this paper is accurate and acceptable, although our model has more samples in the test set. The results demonstrate the feasibility and powerful ability of the chain segment structures as representative of polymers for developing Tg models of polystyrenes. <![CDATA[Nanocomposites films obtained from protein isolates of mechanically deboned chicken meat added with montmorillonite]]> Abstract The aim of this study was to evaluate the properties of nanocomposite films of protein isolates from mechanically deboned chicken meat with organoclay (montmorillonite). For the film development, a 23 experimental design was performed with three levels, protein isolate (2, 3.5, 5 g.100 mL-1 of solution), montmorillonite (0.3, 0.5, 0.7 g.100mL-1 of solution) and glycerol (25, 30, 35 g.100 mL-1 CPI). The tensile strength varied between 6.7 and 9.1 MPa, elongation to break from 26-66%, opacity of 13.1 to 35.7 and solubility from 38.5% to 81.8%. Assessing the structural properties, interleaving of the isolate and montmorillonite can be noted. The results obtained in the experimental design indicate that 2.0 g of CPI.100 g-1 of solution, 0.8 g of MMT.100 g-1of solution and 0.2 g of glicerol.100 g-1CPI are the ideal parameters for preparing nanocomposite films. <![CDATA[<em>In vitro</em> and <em>in vivo</em> cell tracking of PKH26-labeled osteoblasts cultured on PLDLA scaffolds]]> Abstract The importance of monitoring in vivo interaction that occurs between cells /bio/tissue recipient in the understanding of tissue regeneration processes becomes ever greater. This study aims to monitor and evaluate the influence of scaffold implants of poly (L-co-D, L lactic acid) - PLDLA synthesized in the laboratory, previously cultured with primary osteoblastic cells heterologously stained with the fluorescent vital dye, PKH26, on the tissue regeneration process in 8 mm central critical defects of the Wistar rat calvaria. The results obtained by MTT assay and monitoring of cells stained with PKH26 dye over 14 days of culture showed that the dye was cytocompatible with osteoblastic cells and did not exert a negative influence on the growth of unstained cells. In the in vivo study, macroscopic observations made during deployment times corroborate the results in vitro, as no apparent signs of toxicity were observed in the implanted bone defect area. The use of mobile monitoring with the dye, PKH26 in vivo is an effective strategy for the understanding of cell behaviour in the presence of PLDLA polymer.