Furan resins as replacement of phenolic protective coatings: Structural,mechanical and functional characterization

Phenolic coatings are usually a convenient and economical way to protect metallic materials against wear and corrosion. Furan resins are analogous to phenolics, as they are obtained by replacing formaldehyde by furfural in their formulation. In this work, a furan resin based on furfural and phenol was synthesized and used as an aluminum coating. Thus, toxic emissions of formaldehyde were avoided, while a biobased derivative was used instead. The performance of the proposed resin was compared with the one of a traditional phenolic resin. Physicochemical characteristics including chemical structure, surface polarity and glass transition temperature were evaluated by means of Fourier transform infrared spectroscopy, contact angle measurements and dynamic–mechanical analysis, respectively. Nanomechanical and nanotribological properties were assessed by depth sensing indentation techniques. As well, the corrosion resistance of the furan coating was determined by potentiodynamic polarization tests. The obtained results validate the furan resin as a feasible alternative to phenolics to protect aluminum.     

Ammonium removal from landfill leachate by anodic oxidation

The feasibility of removing ammonium from landfill leachates by electrochemical oxidation was studied. Raw leachates and biologically/physico-chemically pretreated leachates from a municipal landfill site were treated. Boron doped diamond was used as anode and stainless steel as cathode, both electrodes with an area of 70 cm(2). The effects of the applied current density (15-90 mA cm(-2)), the initial ammonium concentration (480-2000 mg L(-1)), and the initial chloride concentration were experimentally studied. Total ammonium removal was obtained after 360 min of processing and almost half of the initial ammonium nitrogen was oxidized to nitrate. On the other hand, the concentration of chloride enhanced the rate of ammonium oxidation. In addition, the amount of N-NH(4)(+) transformed into N-NO(3)(-) decreased when additional chloride was provided.     

Yield and biosynthesis of nitrogenous compounds in fruits of green bean (Phaseolus vulgaris L cv Strike) in response to increasing N fertilisation

The objective of the present work was to determine the effect of different dosages of N on the biosynthesis of organic N compounds in fruits and their influence on yield in green bean (Phaseolus vulgaris L cv Strike) plants. The nitrogen was applied to the nutrient solution as NH₄NO₃ at 1.5 (N1), 3 (N2), 6 (N3), 12 (N4), 18 (N5) and 24 mM (N6). Treatment N3 was considered optimal for efficient yield in green bean plants and also for the null presence of NO₃^?. Highest N dosages (18 and 24 mM ) resulted in the accumulation of NO₃^? in pods and seeds. This accumulation encouraged nitrate reductase (NR) and nitrite reductase (NiR) activity in both tissues and treatments, and therefore NR activity might be considered as a good bioindicator of the presence of NO₃^? in edible fruits. The greater NH₄⁺ assimilation by glutamine synthetase (GS) and glutamate synthase (GOGAT) occurred primarily in the pods of the N6 treatment, while the seeds acted as physiological sinks, these latter tissues presenting the highest concentrations of amino acids, proteins and organic N. The high accumulation of NO₃^? and NH₄⁺ in both seeds and pods could be the direct cause of the reduction in fruit production, indicating that green bean plants are very sensitive to high N levels. Copyright © 2004 Society of Chemical Industry     

In vitro toxicity evaluation of hydrogel–carbon nanotubes composites on intestinal cells

Composite materials based on carbon nanotubes (CNT) and polymeric hydrogels have become the subject matter of major interest for use as carriers in drug delivery research. The aim of this study was to evaluate the in vitro cytotoxicity of the hydrogel–carbon nanotube–chitosan (hydrogel–CNT–CH) composites on intestinal cells. Oxidized CNT were wrapped with chitosan (CH), Fourier transform infrared (FT‐IR) analysis suggest that oxidized CNT interact with CH. Transmission electron microscopy (TEM) images show a CH layer lying around CNT. Chitosan wrapped CNT were incorporated to poly (acrylamide‐co‐acrylic acid) hydrogels. Swelling behavior in buffers at different pH were evaluated and revealed a significantly lower swelling when it is exposed to a acid buffer solution (pH 2.2). Mechanical properties were evaluated by measurements of elasticity and the material with CNT showed better mechanical properties. The incorporation and liberation of Egg Yolk Immunoglobulin from hydrogel–CNT–CH were also assessed and it revealed an improved performance. To evaluate the effect of these nanocomposites on cellular redox balance, intestinal cells were exposed to hydrogel–CNT–CH composites and antioxidant enzymes were assessed. Cytotoxicity and apoptosis were also evaluated. Hydrogel–CNT–CH composites induce no oxidative stress and there were no evidence of cytotoxicity or cell death. These preliminary findings suggest that hydrogel–CNT–CH composites show improved properties and good biocompatibility in vitro making these biomaterials promising systems for drug delivery purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41370.     

Fabrication of co‐continuous poly(ε‐caprolactone)/polyglycolide blend scaffolds for tissue engineering

The apparent inability of a single biomaterial to meet all the requirements for tissue engineering scaffolds has led to continual research in novel engineered biomaterials. One method to provide new materials and fine‐tune their properties is via mixing materials. In this study, a biodegradable powder blend of poly(ε‐caprolactone) (PCL), polyglycolide (PGA), and poly(ethylene oxide) (PEO) was prepared and three‐dimensional interconnected porous PCL/PGA scaffolds were fabricated by combining cryomilling and compression molding/polymer leaching techniques. The resultant porous scaffolds exhibited co‐continuous morphologies with ～50% porosity. Mean pore sizes of 24 and 56 μm were achieved by varying milling time. The scaffolds displayed high mechanical properties and water uptake, in addition to a remarkably fast degradation rate. The results demonstrate the potential of this fabrication approach to obtain PCL/PGA blend scaffolds with interconnected porosity. In general, these results provide significant insight into an approach that will lead to the development of new composites and blends in scaffold manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42471.     

Sulfate threshold target to control methylmercury levels in wetland ecosystems

Sulfate contamination has a significant environmental implication through the stimulation of toxic hydrogen sulfide and methylmercury (MeHg) production. High levels of MeHg are a serious problem in many wetland ecosystems worldwide. In the Florida Everglades, it has been demonstrated that increasing MeHg occurrence is due to a sulfate contamination problem. A promising strategy of lowering the MeHg occurrence is to reduce the amount of sulfate entering the ecosystem. High surface water sulfate concentrations in the Everglades are mainly due to discharges from the Everglades Agricultural Area (EAA) canals. Water and total sulfur mass balances indicated that total sulfur released by soil oxidation, Lake Okeechobee and agricultural application were the major sources contributing 49,169, 35,217 and 11,775 mtons year^− 1, respectively. Total sulfur loads from groundwater, levees, and atmospheric deposition contributed to a lesser extent: 4055; 5858 and 4229 mtons year^− 1, respectively. Total sulfur leaving the EAA into Water Conservation Areas (WCAs) through canal discharge was estimated at 116,360 mtons year⁻¹, and total sulfur removed by sugarcane harvest accounted for 23,182 mtons year^− 1. Furthermore, a rise in the mineral content and pH of the EAA soil over time, suggested that the current rates of sulfur application would increase as the buffer capacity of the soil increases. Therefore, a site specific numeric criterion for sulfate of 1 mg L^− 1 was recommended for the protection of the Everglades; above this level, mercury methylation is enhanced. In parallel, sulfide concentrations in the EAA exceeded the 2 μg L^− 1 criterion for surface water already established by the U.S. Environmental Protection Agency (EPA).     

Correlations between structural,barrier, thermal and mechanical properties of plasticized gelatin films

The aims of this work were to develop gelatin films using glycerol as plasticizer (0–100% based on protein mass) and to establish relationships between glycerol content and structural, barrier, thermal and mechanical film properties. These correlations were established since WVP exhibited a minimum for films containing 20 g glycerol/100 g gelatin, while flexibility increased from 2.2% to 180.9% and T_g shifted from 137.5 to 21.3 °C, for films without glycerol and plasticized films with 80 g glycerol/100 g gelatin, respectively. Furthermore, a satisfactory fit between T_g experimental data and predicted values by Couchman and Karasz's equation was found, with glycerol ranging from 0 to 60 g/100 g gelatin. T_g values correlated inversely with film moisture content, and both mechanical and thermal properties showed a strong dependence since elastic modulus and T_g followed a similar trend. Films exhibited similar X-ray patterns regardless of the glycerol concentration, showing a displacement in the position of the peak located at around 2θ = 8°, which shifted towards lower 2θ values with glycerol content.The abovementioned correlations between film physical properties and glycerol content, would allow to select the optimum conditions to develop, process and manage gelatin films according to specific requirements.Industrial relevanceThe methodology used in this work is of considerable importance for the film development and could be used in industrial applications. The management of film formulations and the function that each component plays could allow to obtain tailormade films. A series of relationships between film properties based on gelatin was found, as well as between these properties and glycerol content of the films. An inflexion point in the behavior and microstructure of these materials was established due to glycerol concentration. The addition of higher quantities of glycerol than that corresponds to the abovementioned point, would not be recommendable since the properties are not modified and moreover, it is not profitable. These results would allow better management of film formulations and an appropriate selection of plasticizer concentration in accordance with the specific requirements of potential users.     

Controlled delivery of propionic acid from chitosan films for pastry dough conservation

A study was undertaken to evaluate the feasibility of using chitosan active films designed to control the release of an antimicrobial agent. In this context, the efficacy of propionic acid as both a medium for chitosan dissolution and an antimicrobial agent was examined. This work was focused on studying the potential application of chitosan active films developed to conserve a pastry dough product, modeling the release profile and evaluating the effectiveness of the active agent by extending the product shelf life.