Influence of electroosmotic treatment on the hydro-mechanical behaviour of clayey silts: preliminary experimental results

Preliminary results of an investigation focused on the influence of electrokinetic treatment on the mechanical and hydraulic behaviour of clayey soils are presented. The experimental programme aims at providing a contribution to the sustainability of contaminant extraction or containment via electroosmosis. Changes in the hydraulic and mechanical properties of two illitic clayey soils, subjected to a DC electric field, were investigated. Samples of the two soils were subjected to electrokinetic filtration, for different periods of time, and under different constant loads. Afterwards, they were tested under one-dimensional compression to detect changes in stiffness and hydraulic conductivity due to the electrical treatment. After the application of a DC field for a few hours, a small reversible increment in the average soil stiffness was observed, with respect to the untreated soil, while the hydraulic conductivity was not affected substantially. Dramatic changes of the mechanical and hydraulic soil properties, correlated to changes of the soil pH, were observed following non-conditioned electrokinetic treatment with duration of the order of days.     

Synthesis and aqueous solution behaviors of sodium sulfonate‐terminated dendritic poly(ester‐amine)

Sodium sulfonate‐terminated dendritic poly(ester‐amine) (SPEA) was synthesized by sulfonation of acrylic double bond‐terminated dendritic poly(ester‐amine) (APEA) with sodium hydrogen sulfite (NaHSO₃) in mixture of diglycol and 2‐butanone under normal pressure. The structure of SPEA was characterized by IR, ¹H‐NMR, and elemental analysis. SPEA was water‐soluble. 1.0–40.0% (mass) SPEA aqueous solutions appeared as dilatant fluid. When pH value varied from 1.5 to 12.0, the viscosity of 1–5% (mass) SPEA aqueous solutions changed very small, and the electric conductivity almost kept stable within pH 3.0–10.0. The relationship between the viscosity and the concentration of SPEA water solutions was similar to that of NaCl water solutions. The surface tension of SPEA water solutions was lower than that of polyethylene glycol 2000 water solutions with the same concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel blood-compatible waterborne polyurethane using chitosan as an extender

A series of novel block polymers of polyurethane (PU) and chitosan have been prepared in two steps. The first step is the preparation of PU prepolymer, obtained from polytetramethylene oxide glycol (PTMO, M_n = 1000), isophrone diisocyanate (IPDI), and 2,2′-dimethylol propionic acid (DMPA), followed by ionizing PU prepolymer with triethylamine (TEA). The second step involves PU chain-extended by water-soluble chitosan of low molecular weight (M_n = 5000) by self-emulsion polymerization method. The sizes of the latex particles, morphology, and copolymer architecture have been characterized by dynamic light scattering (DLS), general tensile test, infrared spectroscopy (IR), surface contact angle measurement, and transmission electron microscopy (TEM). Furthermore, it shows that the addition of chitosan remarkably increases anticoagulative property of PU elastomers confirmed by the recalcification time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Interfacial polycondensation of diphenolic acid and isophthaloyl chloride

Interfacial polycondensation of diphenolic acid (DPA) and isophthaloyl chloride (IPC) in various solvent/water systems was investigated with tetrabutyl ammonium chloride as a phase transfer catalyst. It was found that a large mass of capsules were formed at the beginning of the reaction for all solvents examined but the capsule morphology and reaction results depended on the solvents. It is believed that the capsule shells make up of the reaction zone and a mechanism of the interfacial polycondensation is proposed accordingly. The effect of the solvents on the reaction was interpreted from the interaction between the polymer and the solvent according to the mechanism. The reaction conditions were optimized, and poly(DPA-IPC) with high intrinsic viscosity was prepared in high yield under the optimal condition. It is an amorphous polymer with glass transition temperature of about 160°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A disposable sensor based on immobilization of acetylcholinesterase to multiwall carbon nanotube modified screen-printed electrode for determination of carbaryl

A simple method has been devised for immobilization of acetylcholinesterase (AChE) covalent bonding to a multiwall carbon nanotube (MWNT)-cross-linked cellulose acetate composite on a screen-printed carbon electrode (SPCE) and a sensitive and disposable amperometric sensor for rapid determination of carbaryl pesticide is proposed. The immobilized enzyme was preserved on this film because of the excellent biocompatibility and non-toxicity of cellulose acetate. Based on the inherent conductive properties of the MWNT, the immobilized AChE had greater affinity for ATCl and excellent catalytic effect in the hydrolysis of ATCl. MWNT improved the interface enzymatic hydrolysis reaction and increased the amperometric response of the sensor. Under optimum conditions, the inhibition of carbaryl on AChE increased linearly with the increasing concentration of carbaryl in two ranges, from 0.01 to 0.5 μg mL⁻¹ and from 2 to 20 μg mL⁻¹, with the correlation coefficients of 0.9985 and 0.9977, respectively. The detection limit was 0.004 μg mL⁻¹ taken as the concentration equivalent to 10% decrease in signal. The sensor showed acceptable stability, accuracy and could be fabricated in batches, thus it is economic and portable. This type of disposable enzyme-based amperometric sensor has extensive application potential in environmental monitoring of pesticides.     

Influence of pencil lead hardness on voltammetric response of graphite reinforcement carbon electrodes

This work studied the voltammetric response of graphite reinforcement electrodes made of different pencil lead hardness. The studies showed that harder graphite leads, regardless of their manufacturer, are more appropriate as electrode material for voltammetric purposes due to their higher peak currents, increasing sensitivity and reproducibility, with ΔEp closer to the theoretical value for a reversible system.     

FEM model of the ohmic resistance of IP-SOFCs

In the present work, the ohmic resistance of an integrated planar-SOFC (IP-SOFC) has been evaluated by developing a model whose equations have been solved numerically through an FEM method. The model allows to estimate the distribution of voltage and current density in the cell. A comparison between simulated and experimental data of area specific resistance is reported, which shows satisfactory agreement. The mathematical model has also been used to carry out some parametric studies for optimisation purposes. Indeed, a reduction in cell pitch length and an increase in electrode thickness are predicted to lead to a reduction in ohmic losses in IP-SOFCs.     

Effect of high temperature alkali cooking on the constituents,structure and thermal degradation of hemp fiber

Degumming of hemp fiber by high temperature alkali cooking was investigated, and the effect of temperature and dosage of alkali on the constituents, structure, and thermal degradation of hemp fiber was also discussed in this work. The morphology, structure, and thermal degradation of hemp fiber after high temperature cooking were investigated through SEM, FTIR, WAXD, and TG analysis. The results indicated that the high temperature cooking process was effective for removing hemicelluloses and lignin and could also improve the thermal stability of cellulose. Crystallinity index of the treated hemp fiber was increased, which was related to the cooking temperature and NaOH dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and structural characterization of methacrylic acid/octadecyl acrylate‐graft‐poly(methylhydrosiloxane) by hydrosilylation

Methylmethacrylate (MMA) and octadecyl acrylate (OA) were grafted to poly(methylhydrosiloxane) (PMHS) by hydrosilylation, respectively, with hexachloroplatinic acid as catalyst, and the former was further hydrolyzed to prepare methacrylic acid (MAA)‐graft‐PMHS under the alkaline condition. Through orthogonal experiment, main factors affecting the graft reaction between OA and PMHS were discussed and arranged in a decreasing order according to their abilities of the effect on the hydrosilylation of OA with PMHS: catalyst dosage, reaction temperature, reaction time, material ratio, and solvent dosage. It was found that the hydrosilylation of OA with PMHS was easier to that of MMA with PMHS. Under optimal conditions, the grafting ratios of MMA with PMHS and OA with PMHS reached about 90 and 95%, respectively. FTIR and ¹H NMR spectra indicated that the hydrosilylation reactions followed the Markovnikov's rule and played a strong preference toward β‐1,2‐addition. The test of contact angle indicated that surface energy of a system was mainly dependent on the polar groups. The surface energy of OA‐graft‐PMHS (35.07 mN/m) was similar to those of PMHS (35.62 mN/m) and polyoctadecyl acrylate (36.57 mN/m), and lower than that of MAA‐graft‐PMHS (43.50 mN/m). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Influence of post‐treatments on the properties of porous poly(vinyl alcohol) membranes

Porous poly(vinyl alcohol) (PVA) membranes were prepared by a phase‐inversion method. The influence of chemical crosslinking and heat treatments on the swelling degree, resistance to compaction, mechanical strength, and morphology of porous PVA membranes was extensively studied. The crosslinking degree and crystallinity of the membranes, calculated from IR spectra, increased with the treatment time. The porosity, calculated on the basis of swelling experiments, showed a decreasing trend for heat‐treated membranes but remained almost at a constant value for crosslinked membranes. Such a change was further proved with scanning electron microscopy pictures. The behavior was explained by the rearrangement of PVA chains during the heat‐treatment process, which led to morphological changes in the membranes. The mechanical properties of the porous membranes in dry and wet states were measured, and a great difference was observed between crosslinked and heat‐treated membranes in the dry and wet states. The crosslinked membranes showed good mechanical properties in the dry state but became fragile in the wet state. On the contrary, the heat‐treated membranes were more flexible in the wet state than in the dry state. This change was explained by the turnaround of inner stress in the systems during the swelling process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008