Search

The iron mine tailings accumulation in dams is an environmental and economic problem. The composite based on high-density polyethylene/iron mine tailing production for the application of wood plastic and some items of domestic plastic industry can be a good alternative to reduce the rejects in the environment. This work presents the influence of the processing methodology in the mechanical, thermal and morphological properties of composites based on the high-density polyethylene/iron mine tailing. Four methodology processing by continuous and/or batch mixing were available. The iron mine tailing particles in the polymer matrix promoted an increase in mechanical strength and thermal stability. Besides, the particles acted as flame retardant. The iron mine tailing materials produced using batch mixing showed more significant modifications in the properties due to the better dispersion of the filler as shown by scanning electron microscopy.

The PHB (poly (3-hydroxybutyrate)) film and nanocomposite act as catalysts in the oxidation of organic compounds, such as methylene blue dye (MB) using UV radiation. The results indicate that the materials produce in situ hydroxyl radicals, which are responsible for the deep oxidation of MB. The results showed for the first time that only the PHB polymer presents good catalytic activity (∼80%), indicating the possibility of avoiding the use of semiconducting metals in the processes. The main effect is the cleavage of the polymer chains which modifies the PHB structure. This effect also promotes the mineralization of the PHB polymer during the process. Thus, the polymer degrades organic molecules present in water and is also transformed without generating pollutant molecules, as shown by the ESI-MS analyzes. This new catalyst concept allows its use for up to 7 cycles efficiently without semiconductor metals.

Etoposide-loaded poly(lactic-co-glycolic acid) implants were developed for intravitreal application. Implants were prepared by a solvent-casting method and characterized in terms of content uniformity, morphology, drug-polymer interaction, stability, and sterility. In vitro drug release was investigated and the implant degradation was monitored by the percent of mass loss. Implants were inserted into the vitreous cavity of rabbits' eye and the in vivo etoposide release profile was determined. Clinical examination and the Hen Egg Test-Chorioallantoic Membrane (HET-CAM) method were performed to evaluate the implant tolerance. The original chemical structure of the etoposide was preserved after incorporation in the polymeric matrix, which the drug was dispersed uniformly. In vitro, implants promoted sustained release of the drug and approximately 57% of the etoposide was released in 50 days. In vivo, devices released approximately 63% of the loaded drug in 42 days. Ophthalmic examination and HET-CAM assay revealed no evidence of toxic effects of implants. These results tend to show that etoposide-loaded implants could be potentially useful as an intraocular etoposide delivery system in the future.

The objective of this research was to fabricate polymeric concretes comprising combinations of epoxy resin, aggregates, and amino-functionalized carbon nanotubes and to evaluate their properties. Polymeric concrete containing unfunctionalized carbon nanotubes (CNTs) was also studied. Thermogravimetric analysis demonstrated the efficiency of the functionalization of the CNTs, as well as the thermal properties of the resin/CNT nanocomposites. The inclusion of CNTs in the polymeric concrete led to a reduced curing time and improved mechanical properties compared to the reference polymeric concrete. A higher compressive strength was obtained with functionalized CNTs than with unfunctionalized nanotubes and to nanocomposites with low CNTs contents. This was attributed to chemical interactions between the resin and the CNTs that promoted a well-dispersed CNTs/matrix.

Nowadays, to develop products with lower impact without harming the environment. The aim of this work was to develop a polymer composite based in thermoplastic starch (TPS), maleate polyethylene (PE- g -MA) and curaua fiber in the proportion of 10%, 20% and 30 wt%. The resulting material was characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), tensile test, scanning electronic microscopy (SEM) and optical microscopy. The developed composite was applied on ceramic blocks and subjected to natural sunlight; its thermal behavior was monitored using infrared thermography. Thermography was effective for identifying temperature differences in samples of polymer composites with different percentages of fiber and allowed to monitor the thermal behavior. The results show that the manufactured composites have potential for use as thermal insulated building element.

In this work, it has been reported the preparation of catalytic systems based on chemically modified niobium oxides and different polymer matrices, polypropylene (PP), poly(3-hydroxibutyrate) (PHB) and polyurethane (WPU). The efficiency of systems as photocatalytis was investigated. Materials prepared from various polymer matrices showed distinct photocatalytic activities. The systems based on PHB matrix and niobium oxihydroxide presenting the best performance among the studies systems, ~ 90% dye removal at 60 min. The results of systems characterization by Scanning Electron Microscopy (SEM), Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) analysis technical have showed that nanoparticles size, their dispersion in the polymeric matrix and interaction polymer-inorganic particles are responsible by changing photocatalysis process. However, for the PHB, structure parameters of matrix are important. The synchrotron radiation was used to investigate the macromolecular structure of the pure polymers and after the incorporation of niobium nanoparticles.

Collagen is an important biomaterial because it has many applications in the biomedical sector. However, the high hydrophilicity of collagen (COL) leads to easy swelling. Thus, controlling this property is highly desirable. In this work, cellulose nanocrystals (CNCs) dispersed in glycerol (GLI) were incorporated in the matrix collagen to tailor the hydrophilicity and mechanical properties. Study of the hydrophilicity of the bio-based nanocomposite was evaluated by contact angle measurement and thermogravimetric analysis. Mechanical analyses showed that CNCs are excellent reinforcing fillers to the collagen matrix. Synchrotron small-angle X-ray scattering was employed to investigate the nanostructures of COL/GLI/CNC nanocomposites and CNC water dispersion. CNC in concentrations up to 1 wt% presents an intermediate shape between a rod and a plane with a 9.34-nm radius of gyration (R g). Bio-based nanocomposites present two different structural levels with two types of particles with very different R gs. At the intermediate power-law regime, a large-scale mass fractal aggregate is observed. In the high-power-law regime, it is observed scattering from primary particles smaller than 1 nm. As the CNC concentration increases, the original particle distorts from a rod to a plate. The cytotoxicity assay indicates that the collagen and nanocomposites did not affect the cell viability of rat calvarial cells in vitro.

In this work, nanostructured niobium oxyhydroxide was dispersed over poly (3-hydroxybutyrate) (PHB), which is a biopolymer, for application as a photocatalyst using visible and UV light. PHB films with different amounts of niobium oxyhydroxide were characterized by diffuse UV–vis reflectance spectroscopy, FTIR-ATR and SEM. The characterizations showed particles of the niobium compound well-dispersed on the polymeric matrix, thus modifying the bandgap value, which improved the photocatalysis process. The material showed excellent catalytic activity (approximately 100% degradation) for the oxidation of methylene blue dye considering the reaction in a continuous flow bath. Moreover, the polymer films were easily removed from the solution after the reaction and reused several times while retaining their high activity. ESI–MS studies showed that the dye removal occurs by the formation of reaction intermediates due to the successive hydroxylation of the dye structure, confirming that the reaction took place improved by photocatalytic conditions.

The glaucoma is an ocular pathology characterized by the increase of intraocular pressure and possibility of retinal degeneration. The treatment is based on the administration of eye drops. However, they do not induce the permanence of drug in the eye, compromising its bioavailability. In this study, inserts based on chitosan and brimonidine tartrate were developed to treat the glaucoma by improving the drug bioavailability. Inserts were characterized using different analytical techniques FTIR, SEM, DSC and WAXS. The in vitro release profile of drug from inserts was evaluated. The in vitro biocompatibility against ARPE-19 and MIO-M1 cells was investigated. The in vivo biocompatibility using the chorioallantoic membrane was also demonstrated. Analytical techniques demonstrated that the amorphous drug was physically dispersed into the polymeric chains without chemical interactions. However, a portion of drug crystals was on the surface of systems. Inserts provided the controlled release of drug for 30 days without a burst effect. Inserts did not induce a deleterious effect to ocular cells, indicating their biocompatibility. They were also well tolerated in vivo , suggesting the absence of toxicity. These inserts could be potential delivery systems to reduce the intraocular pressure and to induce neuroprotective effects in glaucomatous patients.

In this work, Nb2O5 and red mud (RM) were separately added to Portland cement for application as photocatalysts using visible (vis) and ultraviolet (UV) light. The resultant materials, i.e., mortar/RM and mortar/Nb2O5, were characterized by UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy-attenuated total reflectance, thermogravimetry, photocatalytic tests, and scanning electron microscopy. The characterization results showed that the Nb2O5 and RM particles were micrometric and that their mixtures with mortar exhibited homogeneous and uniform morphologies. The addition of the particles modified the bandgap value of mortar and improved its photocatalytic performance. The materials exhibited catalytic activity for the oxidation of methylene blue dye using UV radiation. In addition, the mortar/RM showed the best performance in the removal of methylene blue dye while the photocatalytic activity of Nb2O5 was compromised when it was mixed with mortar. It is noteworthy that cementitious materials with additives have the potential for use in self-cleaning surfaces.

Unfortunately the surname of the fifth author is wrongly published in the original article as Patricia P. de Souza instead of Patricia S. O. Patricio

The present study concerns an innovative technology for the extraction of chromium, which is present in leather industry wastes, to facilitate the application of chromium-free protein (collagen) as a slow-release drug carrier in skin treatment when there are burns, ulcers and infected wounds. The study focuses on the excavation of industrial landfills, which are currently saturated, to recycle residual wet blue leather to obtain purified collagen films. These films, as biocompatible materials, offer great potential as drug carriers. We test here the material's ability to retain/release silver sulfadiazine and its potential to impede the proliferation of various bacteria. The very promising results demonstrate that the material possesses a high capacity for delivery of the drug and great efficiency in inhibiting bacteria proliferation. The obtained results indicate that the treatment proposed for chromium removal is capable of generating a material rich in amino acids that can be transformed into films with no cellular incompatibility, therefore creating a new field of study from a material that presents a serious environmental liability.

In this study a novel approach for improving the photo-stabilization of polymers by incorporation of nanoparticles of a new niobium compound is reported. For the first time, this approach uses the electronic properties of niobium oxyhydroxide to absorb UV light efficiently to avoid the decomposition of the polymers. The innovative results of this work consist of preparing nanoparticles of niobium oxyhydroxide and its modification by treatment with hydrogen peroxide to alter their ability to absorb radiation and act as a photo-stabilizer for preventing polypropylene degradation. Synchrotron radiation was employed: (i) to explore the niobium nanoparticle form and (ii) to investigate the macromolecular structure of neat PP and PP/Nb compounds before and after degradation. The results from this research study using FTIR-ATR, DSC and microscopies, as TEM, SEM and OM, indicate that the incorporation of niobium oxyhydroxide nanoparticles into the PP matrix provides stability against the action of ultraviolet radiation.

In this work, it is proposed a new strategy to improve the dispersion of inorganic fillers in polymeric matrices by producing surface carbon nanostructures. Clay/carbon nanofibers particles were prepared and used as fillers to improve the mechanical and thermal properties of ultra-high molecular weight polyethylene (UHMWPE). Thermogravimetry (TG), differential scanning calorimetry (DSC), elemental analyses, Raman, X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that chemical vapor deposition (CVD) with ethanol at different temperatures, i.e. 700, 800 and 900 °C with and without Fe catalyst, can be used to produce carbon (0.5-3.6 wt.%), mainly as nanofibers, on the clay surface. The use of these clay/carbon particles as fillers in UHMWPE at 1 and 3 wt.% produced an increase in the yield stress from 16 to ca. 20 MPa and Young modulus from 314 MPa for pure UHMWPE to values near 395-408 MPa. Moreover, the presence of the carbon/clay composites led to a strong improvement of the thermal properties of the UHMWPE increasing the decomposition Tonset (degradation start temperature) from 445 up to 472 °C. It was also observed by the crystallization enthalpies that the UHMWPE increased the crystallinity from 55 to 80-85% in the presence of the carbon composites. These results are discussed in terms of the strong interactions of the hydrophobic carbon nanostructures on the clay surface with the polymer hydrophobic chains.

Ultra-high molecular weight polyethylene samples were submitted to dynamical compressive test in a split Hopkinson Pressure Bar. Three thickness/diameter ratio (0.11, 0.44 and 0.64) and two strain rates (3250 s-1 and 6500 s-1) were used to understand how the test set-up influences the stress equilibrium and the constancy of strain rate during the impact. Concepts of stress equilibrium, constancy of strain rate, dynamical stressstrain curves and dynamical mechanical properties of the material were evaluated. All studied samples achieved stress equilibrium, but the samples with smaller ratio achieved it more easily. Nevertheless, samples with the smallest ratio were not able to achieve strain rate constancy. Additionally, dynamical stress-strain curves were plotted to investigate the mechanical properties of this material at high strain rates. T-tests pointed out that the properties are controlled by the strain rate rather than by the specimen’s thickness/diameter ratio.

A synthetic niobia was modified by treatment with hydrogen peroxide to be used as a catalyst for converting glycerol into petrochemical compounds. The catalytic properties of niobium oxyhydroxide were obtained by generating acidic and oxygenated groups (peroxo groups) on the solid surface. Compounds like ethers and allyl alcohol were obtained. A very active H2O2-modified catalyst showed high activity for the oxidation and dehydration of 91% of glycerol conversion using H2O2 and 46% of allyl alcohol selectivity in volatile phase. The product was analyzed by gas chromatography-mass spectrometry (GC-MS), thermogravimetry-mass spectrometry (TGA-MS) and nuclear magnetic ressonance (NMR). These results strongly suggest that the reactions involve acid and oxidizing species generated after the reaction of niobium with H2O2. 1H and 13C multidimensional NMR spectroscopy confirmed the results obtained with GC-MS and showed the production of several compounds after niobia treatment.

Collagen (Col) is extensively used in various applications, including pharmaceutical, agricultural, and food applications. The materials based in Col may exhibit properties of biomedical interest because of their low toxicity, high structural capacity support, controlled biodegradability, and biocompatibility. However, Col has poor thermal and mechanical properties. The addition of plasticizers (Plas's) and fillers is an established strategy for enhancing the properties of the resulting nanocomposites. In this study, nanocomposites based on Col and cellulose nanocrystals were developed in two different ways and with three different Plas's. These materials were subjected to structural, thermal, mechanical, and morphological analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44954.

Materials that can switch from stiff to soft or from brittle to tough by slightly changing the temperature, pH, electric, or magnetic fields of their environments, can have a pronounced impact on many applications, including sensors, biomedical materials for less invasive surgeries, and packaging materials. In this work, temperature-sensitive poly(N-isopropyl acrylamide) grafts and low molar mass polyethylene glycol were incorporated in the interfacial region between clay nanoparticles and a bacteria-derived polyhydroxybutyrate matrix to determine if the application of an external stimulus, such as small changes in temperature, could increase the toughness of the nanocomposites. The obtained materials were characterized by using thermal analysis, infrared spectroscopy, dynamic light scattering and dynamic mechanical tests. Mechanical properties were also evaluated at different temperatures and showed that small changes in temperature, such as from 25°C to 40°C, led to a pronounced increase in strain at break of the nanocomposites containing the modified interface. The external stimulus associated with the increase in temperature from 25°C to 40°C can reduce the interfacial interactions between clay and polymer matrix and create a highly plasticized polymer layer between the components of the nanocomposite, which favored the sliding of the interface and ultimately led to high values of elongation. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

O polipropileno (PP) tem uma degradação natural lenta e representa um importante constituinte na gestão dos resíduos sólidos, enquanto o poli(hidroxibutirato) (PHB) é um polímero biodegradável, mas tem as desvantagens de dificuldade de processamento e custo. O objetivo deste trabalho foi avaliar o efeito de nanopartículas de TiO2, do método de processamento e do envelhecimento acelerado na estrutura e propriedades da mistura PP/PHB/TiO2. As amostras foram produzidas por etapas de extrusão e injeção e foram caracterizadas por MEV/EDS, FTIR e análise térmica. Os resultados mostraram que a incorporação de 3% de nanopartículas de TiO2 levou a um aumento do tamanho médio da fase dispersa rica em PHB. A mudança na sequência da adição de nanopartículas de TiO2 permitiu guiar a incorporação desses nanocomponentes para a fase rica em PP. As misturas produzidas se mostraram mais estáveis termicamente do que PHB puro e a adição de TiO2 foi eficaz em aumentar a estabilidade térmica dos compósitos. As análises termogravimétricas e por FTIR mostraram que blendas contendo nanopartículas de TiO2 tiveram sua degradação mais afetada nos ensaios de envelhecimento acelerado. Os ensaios de extração com solvente mostraram que um maior conteúdo de produtos de fotodegradação puderam ser extraídos de amostras contendo mais elevadas concentrações de TiO2. Polypropylene (PP) has a slow natural degradation rate. On the other hand, poly(hydroxybutyrate) (PHB) is biodegradable but has the disadvantages of cost and difficulty of processing. The aim of this work was to evaluate the effect of TiO2 nanoparticles, processing conditions and accelerated aging on the structure and properties of PP/PHB/TiO2 mixtures. Samples were prepared by extrusion and injection molding. The incorporation of 3% TiO2 nanoparticles led to an increase in the average size of the dispersed phase rich in PHB. Changes in the sequence of TiO2 nanoparticles incorporation were able to guide the inclusion of nanoparticles to the PP-rich phase. The produced composites were more thermally stable than pure PHB and the incorporation of TiO2 was effective to increase the thermal stability of the composites. Thermal and FTIR analyses showed that blends containing TiO2 nanoparticles had their degradation more affected by accelerated aging treatments. Solvent extraction results revealed that a larger amount of soluble products from the photodegradation could be extracted from samples containing TiO2 submitted to accelerated aging treatments.

Here, we show that a new niobium oxyhydroxide, NbO2OH, can be synthesized and modified with a surfactant to be used as a heterogeneous catalyst for oxidative desulphurization. The material was treated with hydrogen peroxide to generate oxidizing groups (peroxo species) on the surface. Furthermore, this material was converted to a family of solid catalysts that can stabilize water/oil emulsions and catalyze reactions at the liquid/liquid interface by anchoring a surfactant to the catalyst. The material was then able to efficiently remove a sulfurous compound under mild conditions.

In tropical countries where rainfall rates are high, and especially in deforested areas in the Atlantic Rainforest and Cerrado in southeastern Brazil, water is the dominant driving force of erosion. The most common method used to restore degraded tropical lands is to plant nursery-raised tree seedlings, but this method is not always practical and a variety of newer reforestation techniques have become available. Biodegradable coir geotextiles combined with native seeds can be used to restore degraded forest areas. The effects of the climatic conditions during a seasonal cycle of rain and drought were evaluated on the structural and mechanical properties of coir geotextile fibers that were treated, or not, with lime. Analyses of the tensile strength of coir fibers showed that after 12 months of exposure untreated fiber had retained 23% and treated fiber 19% of their initial strength. Two principal factors were considered in evaluating the structural properties of the coir fibers after environmental exposure: (i) initial cellulose retention and its stability after lime-treatment; (ii) lignin degradation and/or its loss to the environment. The structural changes seen by thermogravimetry (TGA) and Fourier Transforms in Infrared spectroscopy (FTIR) analyses explained the changes seen in coir mechanical properties. The greater cellulose contents of fiber structures treated with lime explained their greater tensile strength and high Young's modulus measures after the first three months of exposure in local weather conditions. Considering that lime treatment improved coir fiber properties, lime applications are indicated when coir geotextiles are to be used in acidic Brazilian Cerrado soils.

Polyurethane waterborne synthesis was performed using a two-step method, commonly referred to as a prepolymer method. Nanocomposites based on waterborne polyurethane and cellulose nanocrystals were prepared by the prepolymer method by altering the mode and step in which the nanofillers were incorporated during the polyurethane formation. The morphology, structural, thermal, and mechanical properties of the resulting nanocomposite films were evaluated by Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and tensile tests. FTIR results indicated that the degree of interaction between the nanofillers and the WPU through hydrogen bonds could be controlled by the method of cellulose nanocrystal incorporation. Data obtained from SAXS experiments showed that the cellulose nanocrystals as well as the step of the reaction in which they are added influenced the morphology of the polyurethane. The reinforcing effect of CNCs on the nanocomposites depends on their morphology.

Materials based on a mixture of poly(vinylidene fluoride) (PVDF), poly(2-hydroxyethyl methacrylate) (PHEMA) and LiClO4 were produced to evaluate their ionic behavior and morphological structure to determine if they can be used as an electrolyte in electrical devices. FTIR chemical analysis results indicated the presence of interactions between PVDF, PHEMA and LiClO4. MDSC results showed that the transition temperatures of the polymers shifted to higher temperatures for systems containing high concentrations of each polymer. SEM images indicated that there was some miscibility between the polymers especially for the 25 and 75 wt. % compositions. In terms of the electrical performance, the ionic conductivity level of the electrolyte could be controlled by changing the composition of the system.

Methotrexate (MTX) is used in the treatment of malignancies; however, its clinical application is limited by its toxic dose-related side effects. An alternative to overcome the toxicity of the MTX in healthy tissues is the design of an implantable device capable of controlling the delivery of this drug for an extended period within the tumor site.To develop methotrexate-loaded poly(ε-caprolactone) implants (MTX PCL implants) and to demonstrate their efficacy as local drug delivery systems capable of inhibiting Ehrlich solid tumor bearing mice.MTX PCL implants were produced by the melt-molding technique and were characterized by FTIR, WAXS, DSC and SEM. The in vitro and in vivo release of MTX from the PCL implants was also evaluated. The efficacy of implants in inhibiting tumor cells in culture and the solid tumor in a murine model was revealed.The chemical and morphological integrity of the drug was preserved into the polymeric matrix. The in vitro and in vivo release processes of the MTX from the PCL implants were modulated by diffusion. MTX diffused from the implants revealed an antiproliferative effect on tumor cells. Finally, MTX controlled and sustained released from the polymeric implants efficiently reduced 42.7% of the solid tumor in mice paw.These implantable devices represented a contribution to improve the efficacy and safety of chemotherapy treatments, promoting long-term local drug accumulation in the targeted site.

Porous synthetic substrates are developed through tissue engineering technologies to grow new tissue, restoring the function of tissue or an organ. For bone regeneration, these scaffolds must support the dynamic load exerted on this tissue, achieved primarily by increasing their compression strength, as established in the literature. The aim of this paper was to incorporate an inorganic composite bioactive glass (60%SiO2 - 36%CaO - 4%P2O5) as a reinforcing agent in mechanical 3D scaffolds that must remain porous. Two strategies were adopted: a co-precipitation method to obtain a nanoparticulate dispersion of bioactive glass (BGNP) and a sol-gel method to combine a bioactive glass solution (BG) with a previously prepared chitosan polymer solution. Moreover, a lyophilization process was also used, generating highly porous scaffolds. Various aspects of the scaffold were evaluated, including the morphology, orientation and size of the pores, and mechanical strength, as obtained using the two synthetic methods. The data for compressive strength revealed increased strength after the incorporation of bioactive glass, which was more pronounced when utilizing the nanoscale bioactive glass.

In this work, blends of poly(3-hydroxybutyrate) (PHB) with 5, 10, 15, and 20 wt % low molecular weight poly(propylene glycol) (LMWPPG) have been prepared and characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) with attenuated total reflectance (ATR) accessory and simultaneous thermal analysis (TG/DTA). FTIR and thermal analyses suggested that the presence of LMWPPG led to a maximum crystallinity for the blend PHB/PPG (90/10) blend. The presence of LMWPPG also caused a significant increase of the PHB processability window, i.e., the difference of the melting and degradation temperature, of PHB from 105 to 134°C, which is extremely important for the industrial uses of PHB. This PHB stabilization effect is discussed in terms of an intermolecular interaction of the PHB carbonyl with LMWPPG methyl groups which probably hinders the classical radon β-scission PHB intramolecular decomposition mechanism. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Bionanocomposites based on polyhydroxybutyrate (PHB) and cellulose nanowhiskers (CNWs) were prepared by dispers- ing CNWs in poly(ethylene glycol) (PEG) plasticizer subsequently incorporating the CNWs/PEG suspensions in the matrix. The ther- mal properties of the nanocomposites indicate an enlargement in the processing window in comparison to the neat PHB. The nano- composites showed a remarkable increase in the strain level (50 times related to the neat PHB), without a significant loss of the tensile strength with the incorporation of small concentrations of CNWs in the final nanocomposite (up to 0.45 wt %). This behavior was explained in terms of a considerable chain orientation promoted by the presence of CNWs in the same direction of the applied load, which activated shear flow of the polymer matrix. The results described here can be explored to extend the applications of this biopolymer. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 3613-3621, 2013

Direct compression is one of the most popular techniques to prepare tablets but only a few commercial excipients are well adapted for this process into controlled release formulations. In the last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluated the physicochemical and flow properties of new polymeric excipient of ethyl acrylate, methyl methacrylate and butyl metacrylate, synthesized by suspension polymerization using cellulose nanowhiskers as co-stabilizer, to be used as direct compression for modified release tablets. Infrared spectroscopy (FTIR) confirmed the success of the copolymerization reaction. Scanning electron microscopy (SEM) showed that excipient was obtained how spherical beads. Thermal properties of the beads were characterized by thermogravimetric (TG) analysis. Particle size analysis of the beads with cellulose nanowhiskers (CNWB) indicated that the presence of the nanowhiskers led to a reduction of particle size and to a narrower size distribution. In vitro test showed that the nanowhiskers and beads produced are nontoxic. Parameters such as Hausner ratio, Carr's index and cotangent of angle α were employed to characterize the flow properties of CNWB beads. Furthermore, the beads are used to produce tablets by direct compression contained propranolol hydrochloride as model drug. Dissolution tests performed suggested that beads could be used as excipient in matrix tablets with a potential use in drug controlled release.

Self-sustained cast films formed from heterogeneous blends of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) conjugated polymer and thermoplastic polyurethane (TPU) were investigated by photoluminescence (PL) and scanning electron microscopy (SEM). A blue shift is observed for the pure electronic transition PL peak (E00) with decreasing MEH-PPV concentration. The two clear shoulders in the PL spectra at higher energy than the E00 peak appear due to the formation of small conjugation segments of the MEH-PPV molecules at the interface of the spherical MEH-PPV domains. This assumption and the origin of the blue shift were confirmed by correlating the average size of the MEH-PPV domains, observed from SEM images, and the analysis of the PL spectra at low temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Polyurethane (PU) and polyurethane–poly(methylmethacrylate) (PMMA) blend membranes were used in gas separation studies. The effects of blend composition, temperature, and pressure on the permeability, diffusivity, and solubility of CO2, H2, O2, CH4, and N2 were investigated. The separation factors of some gas pairs were also evaluated. Positron annihilation lifetime spectroscopy was applied to assess free volume changes as a function of blend composition and temperature. Free volume size increases by approximately 30% with increasing temperature from 10 to 40 °C for all blends studied. The permeability of all gases decreases by approximately 55% with the addition of 30 wt% of PMMA. The permeation process is governed by diffusion, except that of CO2. In relation to the behavior of gas transport as a function of temperature, some important observations are (i) CO2 presents the lowest permeation activation energy value (28 kJ/mol), and (ii) gas pair selectivity increases at low temperatures and is high for gas pairs that present differences in permeation activation energies as high as 15 kJ/mol for the CO2/CH4 gas pair. Furthermore, the study with pressure variations shows that: (i) at elevated pressure, the PU and the blend membrane permeability to CO2 and H2 increases by approximately 35%, and (ii) oxygen-to-nitrogen selectivity increases with pressure as a consequence of the decrease in the permeability to nitrogen in the case of the 30%-PMMA blend.

Electric force microscopy (EFM) was employed in the electrical characterization of a blend of thermoplastic polyurethane (TPU) and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) conjugated polymer. Although qualitative EFM interpretation is straightforward, its quantitative analysis always relies on approximated models. The extraction of physically reasonable parameters is normally assumed as a proof of validity of the theoretical model employed. In order to gather information about electric properties of this blend and to test the EFM technique itself, two distinct and discordant models were developed in this work to fit experimental EFM data. Even though MEH-PPV is regarded as a conductor in one model and as a dielectric in the other, both models yielded coherent and reasonable electrical properties for this blend. Such unexpected results are used to discuss the robustness or frailty of EFM in the analysis of complex materials.

A polymer blend based on thermoplastic elastomeric polyurethane and polymethylmethacrylate (TPU/PMMA) has been studied by positron annihilation lifetime spectroscopy (PALS) and thermomechanical analysis. Thermomechanical analysis allowed the determination of two glass transitions for the blends in the overall range of compositions. The first one (Tg1) showed a constant value of −45°C for all blends, the same value of the pure TPU. The second glass transition (Tg2), which is associated with a PMMA rich phase, presented variations with composition. Tg2 showed minimum values for the blends in the 20–40 wt % TPU range, which indicates increase of interaction in this composition region. PALS systematic investigation allowed the determination of relative mean free volume fractions, fv/C, and binary interchain interaction parameters, β. These parameters exhibited a noticeable negative deviation from additivity in all range of composition and minima for the 20 wt % TPU blend. PALS results were interpreted as associated to a strong attractive interchain interaction between TPU and PMMA in the PMMA rich phase which contracts the free volume fraction of the blends. Moreover, the miscibility achieved in the PMMA rich phase would allow a good adhesion between this phase and the TPU phase, which was corroborated by scanning electron microscopy images. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

PU and PU/PMMA blends were studied by Fourier transform infrared spectroscopy (FTIR), temperature modulated differential scanning calorimetry (TMDSC), scanning electron microscopy (SEM) and positron annhililation lifetime spectroscopy (PALS), and applied as membranes to the permeation of the gases H2, N2, O2, CH4, and CO2. The blend materials presented partial miscibility associated with hydrogen bond interaction between urethane and PMMA. Polyether flexible segment glass transition was observed at −51 °C and no significantly changes with PMMA content were observed in PU continuous phase in the blends. On the other hand, a PMMA rich phase presented glass transitions between 74 and 90 °C for blends with 80, 60, 40, and 20 wt% PU. Pure PMMA shows Tg of 117 °C. Besides, it was observed a broad thermal event that can be assigned to the interphase between the pure PU phase and the PMMA rich phase. PALS results showed a decrease in the average free volume size of the blends with increasing PMMA content for blends with 80 and 60 wt% PU. In addition, the relative free volume content of the samples does not change significantly. The blends with 90, 80, 70, and 60 wt% PU showed lower permeabilities than those of the PU membrane. The decrease in permeability is well correlated with the decrease in average free volume size. In the case of the H2/N2 gas pair, selectivity increases with blend PMMA content, and no marked changes are observed for the other gas pairs. The improvement in H2 selectivity is associated with the increase in rigid amorphous phases, which induces a complex phase-separated morphology in the blends.

Recent studies in tissue engineering have highlighted the importance of the development of composite materials based on biodegradable polymers containing bioactive glasses, in particular, composites for high load support and excellent cell viability for potential application in bone regeneration. In this work, hybrid composite films were obtained by combining chitosan with bioactive glass in solution form and in nanoparticle dispersion form obtained by the two different synthesis routes: the sol-gel method and coprecipitation. The bioactive glass served both as a mechanical reinforcing agent and as a triggering agent with high bioactivity. The results ofin vitroassays with simulated body fluid demonstrated the formation of a significant layer of fibrils on the surface of the film, with a typical morphology of carbonated hydroxyapatite, reflecting induction of a favorable bioactivity. Maximum tensile stress increased from 42 to 80 MPa to the sample with 5% wt bioactive glass. In addition, samples containing 5% and 10% wt bioactive glass showed a significant increase in cell viability, 18 and 30% increase compared to the control group. The samples showed significant response, indicating that they could be a potential material for use in bone regeneration through tissue engineering.

In this work, nanocomposites were obtained by the dispersion of niobium oxyhydroxide into a poly(3-hydroxybutyrate) (PHB) matrix by different preparative methods. These methods led to changes in the polymer morphology and in their photocatalytic properties. Thermal and structural properties of the nanocomposites were investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR)–attenuated total reflection (ATR). Scanning electron microscopy images were analyzed in order to observe the different morphologies of nanocomposites as well as the distribution of niobium nanoparticles in the PHB matrix. The chemical interactions between the polymer and niobium nanoparticles were observed in the FTIR–ATR and thermal analyses. The results of TGA and DSC indicated an improvement in the thermal stability of the polymer and the action of inorganic nanoparticles as nucleating agents in the process of heterogeneous nucleation of PHB. The composites exhibited good catalytic activity for the removal of methylene blue dye from an aqueous medium (∼90%) during a photocatalytic process. The different morphologies of PHB/niobium oxyhydroxide composites directly influenced the catalytic activity of the material due to the difference in the dispersion of nanoparticles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45836.

Poly(e-caprolactone) implants containing etoposide, an important chemotherapeutic agent and topoisomerase II inhibitor, were fabricated by a melt method and characterized in terms of content uniformity, morphology, drug physical state, and sterility. In vitro and in vivo drug release from the implants was also evaluated. The cytotoxic activity of implants against HeLa cells was studied. The short-term tolerance of the implants was investigated after subcutaneous implantation in mice. The original chemical structure of etoposide was preserved after incorporation into the polymeric matrix, in which the drug was dispersed uniformly. Etoposide was present in crystalline form in the polymeric implant. In vitro release study showed prolonged and controlled release of etoposide, which showed cytotoxicity activity against HeLa cells. After implantation, good correlation between in vitro and in vivo drug release was found. The implants demonstrated good short-term tolerance in mice. These results tend to show that etoposide-loaded implants could be potentially applied as a local etoposide delivery system.

A novel material based on niobia (Nb2O5) was synthesized to oxidize an organic compound in aqueous medium in the presence of H2O2 after chemical modifications. Niobia was modified by doping with tungsten and also treating with H2O2 in order to maximize the oxidative properties of this oxide. The analysis of the products from methylene blue dye oxidation with electrospray ionization mass spectrometry (ESI-MS) showed that the dye was successively oxidized to different intermediate compounds. The successive hydroxylation during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated involving H2O2 on the W-doped niobia grain surface. These results strongly suggest that the H2O2 can regenerate in situ the peroxo group remaining active the system. Um novo material à base de nióbia (Nb2O5) foi sintetizado e quimicamente modificado para oxidar compostos orgânicos em meio aquoso, na presença de H2O2. A nióbia foi modificada por dopagem com tungstênio e também tratamento com H2O2 com o intuito de potencializar suas propriedades oxidativas. A investigação dos produtos gerados pela oxidação do azul de metileno, usando a técnica de espectroscopia de massas com ionização por eletrospray (ESI-MS), mostrou que o corante foi sucessivamente oxidado produzindo diferentes compostos intermediários. A sucessiva hidroxilação durante o processo oxidativo indica a alta reatividade dos radicais hidroxilas que são gerados, envolvendo H2O2 sobre a superfície do grão de nióbia dopada com W. Estes resultados sugerem fortemente que o H2O2 pode regenerar in situ o grupo peróxido, permanecendo ativo no sistema.

A correlation between thermal, optical and morphological properties of self-sustained films formed from blends of poly(3-hexylthiophene) (P3HT) and thermoplastic polyurethane (TPU), with 1, 10 and 20 wt% of P3HT in TPU, is established. Images of scanning electron microscopy (SEM) show the formation of domains of P3HT into the TPU matrix, characterizing the blend material as heterogeneous. The heat capacity (C(p)) dependence on P3HT contents was investigated in a large temperature interval. In the region of the TPU glass transition, the difference between the experimental and predicted ΔC(p) values is more pronounced for the 1 wt% case, which strongly suggests that in this case there is a higher influence of the P3HT chains on the TPU matrix. The SEM images for the 1 wt% blended film present the formation of the smallest P3HT domains in the TPU matrix. The relatively high reduction of the PL intensity of the pure electronic transition peak in the 1 wt% blended film, in comparison to the other blended films and also to a pure P3HT film, favours the assumption that the smallest P3HT domains are at the origin of a more structural disordered character. This fact is in agreement with the results obtained by Raman spectroscopy and also by photoluminescence resolved by polarization in stretched self-sustained films, showing an ample correlation between morphological, thermal and optical properties of these blended materials. In addition, the thermoplastic properties of the polyurethane configure very good conditions for tensile drawing of P3HT and other conjugated polymer molecules.

Two types of photopolymerizable and injectable polyurethane acrylates (PUAs), based on poly(propylene glycol) or poly(caprolactone diol) and hydroxyethyl methacrylate, were synthesized and characterized in order to obtain information regarding their use as an injectable material for biomedical applications. Structural characteristics of the biomaterials, including the degree of phase separation, were evaluated by Fourier transform infrared spectroscopy. The viscosities of the obtained biomaterials make them suitable for injection, molding and photopolymerization using visible light, as demonstrated by the injection test. The cured polymers had mechanical properties comparable to those of certain soft tissues, such as skin. An in vitro cell-polyurethane cytotoxicity study was carried out with mesenchymal stem cells from rat tibias and femurs. The proliferation/viability of the cells in the presence of the synthesized material was assessed by the MTT assay, collagen synthesis analysis and the expression of alkaline phosphatase. The results that were obtained through the in vitro tests indicated that PUAs are cytocompatible. The in vivo experiments were correlated with the in vitro tests and showed low levels of toxicity for the obtained biomaterials. Histology cross-sections showed that the biomaterials induced no significant inflammatory reaction. Our study demonstrates the potential for using synthesized photocurable polyurethanes in biomedical applications. Furthermore, the obtained injectable polymer systems employ minimally invasive procedures and can be molded in situ before photopolymerization with visible light.

Layer-by-layer (LBL) assembly was used to combine crystalline rod-like nanoparticles obtained from a vegetable source, cellulose nanowhiskers (CNWs), with collagen, the main component of skin and connective tissue found exclusively in animals. The film growth of the multilayered collagen/CNW was monitored by UV-Vis spectroscopy and ellipsometry measurements, whereas the film morphology and surface roughness were characterized by SEM and AFM. UV-Vis spectra showed the deposition of the same amount of collagen, 5 mg m−2, in each dipping cycle. Ellipsometry data showed an increment in thickness with the number of layers, and the average thickness of each bilayer was found to be 8.6 nm. The multilayered bio-based nanocomposites were formed by single layers of densely packed CNWs adsorbed on top of each thin collagen layer where the hydrogen bonding between collagen amide groups and OH groups of the CNWs plays a mandatory role in the build-up of the thin films. The approach used in this work represents a potential strategy to mimic the characteristics of natural extracellular matrix (ECM) which can be used for applications in the biomedical field.

Self-sustained and spin-casting films formed from blends of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) conjugated polymer and thermoplastic poly-urethane (TPU) at different concentrations have been investigated. Scanning electron microscopy images of self-sustained films show the formation of circularlike domains of MEH-PPV in the TPU matrix, characterizing the blend material as heterogeneous. The circularlike domains in the spin-casting films were also observed by electric force microscopy (EFM) and by atomic force microscopy. The EFM, in particular, has allowed the differentiation of the MEH-PPV domains from the TPU matrix due to the electrical properties of the conjugated polymer. The MEH-PPV domains in the spin-casting films are much smaller in size than in the case of self-sustained films. The glass transition temperatures for the TPU and for the self-sustained blended films were obtained by temperature modulated differential scanning calorimetry. A very small variation in ...

FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior O PEAD é polímero amplamente utilizado na indústria, mas apresenta algumas limitações de uso como material de engenharia, em parte em função de sua fragilização sob condições de alta pressão, baixa temperatura e alta velocidade de deformação. O nanotalco sintético ainda é uma carga pouco estudada, mas exibe propriedades lubrificantes atraentes, além de alta área superficial específica e condição nanométrica/submicrométrica apreciáveis, sendo assim, é supostamente uma carga atrativa para o aprimoramento da capacidade de deformação de sistemas poliméricos. Misturas binárias e ternárias de PEAD e PEAD/EVA com a incorporação de 1% m/m de talcos foram preparadas por mistura no estado fundido em extrusora dupla rosca seguido de moldagem por injeção. Três tipos de talcos foram avaliados: microtalco natural (TN), nanotalco sintético semicristalino (NTC) e nanotalco sintético amorfo (NTA). O TN apresentou tamanho micrométrico, enquanto os talcos sintéticos exibiram uma condição submicrométrica/nanométrica, além de alta área superficial específica, até 80 vezes superior ao TN. A investigação de nanocompósitos ternários PEAD/EVA/NTA foi realizada utilizando diferentes técnicas de caracterização. As propriedades térmicas foram examinadas por termogravimetria (TG) e por calorimetria exploratória diferencial (DSC) e mostraram que a estabilidade térmica dos nanocompósitos foi levemente ampliada com a incorporação do NTA. A morfologia dos nanocompósitos ternários, utilizando microscopia eletrônica de varredura (MEV), revelou o NTA profundamente incorporado à matriz polimérica, além de uma distribuição homogênea entre as fases. As amostras com 50% de EVA apresentaram uma morfologia especial, houve mudança de estrutura de mar-ilha para co-contínua, assim como refinamento do tamanho da fase EVA. As propriedades mecânicas dinâmicas das amostras foram analisadas usando um analisador térmico mecânico dinâmico (DMA) e mostraram que o módulo de armazenamento aumentou com um padrão difuso com a adição do NTA, enquanto a curva tan  do nanocompósito ternário 50EVA/NTA mostrou um pico proeminente em torno da Tg do EVA e constatou-se a imiscibilidade entre as fases poliméricas. As propriedades mecânicas das amostras foram estudadas por ensaios de tração e impacto. Um comportamento notável foi verificado para o nanocompósito 50EVA/NTA que manifestou uma característica de super ductilidade, com incremento do alongamento na ruptura de 4,8 e 2,4 vezes com relação ao PEAD puro e sua blenda correlata. A investigação de compósitos binários PEAD/talcos foi conduzida para avaliação do papel dos diferentes tipos de talcos. A estabilidade térmica dos compósitos foi aumentada moderadamente com a incorporação das cargas de talcos. A morfologia dos compósitos binários PEAD/talcos revelou partículas dos talcos sintéticos majoritariamente bem dispersas no PEAD, enquanto o TN apresentou maior incidência de partículas agregadas. Os resultados de DMA mostraram que a adição dos talcos ao PEAD puro provocou aumento apreciável do módulo de armazenamento em uma ampla faixa de temperatura. As curvas tan  indicaram que comportamento de amortecimento dos compósitos ficou relativamente reduzido. Os ensaios de mecânicos exibiram um leve incremento do módulo de elasticidade e queda moderada da resistência à tração e da resistência ao impacto, enquanto a ductilidade exibiu ganho expressivo para a amostra PEAD/NTA, com incremento de 50% quando comparado ao PEAD puro. A pesquisa evidenciou que o NTA, com um baixo nível de concentração, pode ser usado como uma carga diferenciada, de expressiva efetividade, para melhoria da ductilidade e do equilíbrio rigidez/deformabilidade do PEAD e de blendas PEAD/EVA. Essa nova característica habilita o PEAD à novas aplicações onde propriedades mecânicas superiores são requeridas, especialmente ductilidade, assim como qualifica o NTA como um agente lubrificante promissor, com potencial de atender à requisitos mecânicos de outros sistemas poliméricos. HDPE is a polymer widely used in industry, but it has some limitations of use as engineering material, a portion due to its fragility mainly under conditions of high pressure, low temperature and high deformation speed. The synthetic nanotalc is still a poorly studied filler, but it exhibits attractive lubricating properties, in addition to a high surface area and appreciable nanometric/submicrometric condition, so it is supposedly an attractive filler for improving the deformation capacity of polymeric systems. Binary and ternary blends of HDPE and HDPE/EVA with the incorporation of 1% m/m of talcs were prepared by mixing in the molten state in a twin-screw extruder followed by injection molding. Three types of talc were evaluated: natural microtalc (TN), semicrystalline synthetic nanotalc (NTC) and amorphous synthetic nanotalc (NTA). The TN had a micrometric size, while the synthetic talc showed a nanometric/submicrometric condition and with a specific surface area about 80 times greater than the TN. The investigation of HDPE/EVA/NTA ternary nanocomposites was carried out using different characterization techniques. The thermal properties were examined by thermogravimetric analysis (TG) and by differential scanning calorimetry (DSC) and showed that the thermal stability of the nanocomposites was slightly improved with NTA incorporation. The morphology of the nanocomposites, using scanning electron microscopy (SEM), revealed the NTA deeply embedded in the polymer matrix, a homogeneous distribution between the phases, in addition to changing the morphology of the 50EVA/NTA sample from sea-island to co-continuous, as well as refinement of size of the EVA phase. The dynamic mechanical properties of the samples were analyzed using the dynamic mechanical thermal analyzer (DMA). The results showed that the storage modulus increased with a diffuse pattern with NTA addition, while the tan  curve showed a prominent peak for the nanocomposite with 50% m/m of EVA (50EVA/NTA) around the EVA Tg, besides immiscibility between the polymeric phases. The mechanical properties of nanocomposites were studied by tensile and impact tests. A remarkable behavior was verified for the 50EVA/NTA nanocomposite that showed a super ductility characteristic, with an increase in the elongation at rupture of 4.8 and 2.4 times in relation to the pure HDPE and the related blend. The investigation of HDPE/talc binary composites was conducted to evaluate the role of different types of talc. The thermal stability of the composites has moderately improved with the incorporation of talcs. The morphology of the binary composites revealed that the particles of the synthetic talcs were normally homogeneously dispersed and deeply incorporated into the HDPE, whereas the TN presented higher levels of aggregated particles. DMA results showed that the addition of talcs to pure HDPE caused an appreciable increase in the storage modulus over a wide temperature range. The tan  curves indicated that the damping behavior of the composites was relatively reduced. The mechanical tests indicated that the composites showed a slight increase in the elastic modulus. However, composites showed a moderate drop in tensile strength and impact resistance, while ductility showed a significant gain for the HDPE/NTA sample, with an increase of 50% when compared to pure HDPE. The research evidenced that the NTA, with a low-level concentration, can be used as a differentiated filler, of high effectiveness, to improve the ductility and the stiffness/deformability balance of HDPE and HDPE/EVA blends. This new feature enables HDPE to new applications where superior mechanical properties are required, especially ductility, as well as qualifying NTA as a promising lubricating agent, with the potential to meet the mechanical requirements of other polymeric systems.