Terms Of Water Uptake Research Articles

Water diffusion and hydrolysis effect on the structure and dynamics of epoxy-anhydride networks

Epoxy-anhydride networks have been analyzed in terms of water uptake and degradation behavior by means of broadband dielectric spectroscopy and atomic force microscopy. It has been found that water absorption produces a chemical reaction in the polymer networks, in turn causing a plasticizing effect and changing their mechanical properties. We demonstrate that a non invasive dielectric spectroscopy analysis of the segmental dynamics can be performed in order to quantitatively describe the degradation effects, as well as their influence in the mechanical properties at the nanoscale.

Magnetic silk fibroin e-gel scaffolds for bone tissue engineering applications

Recently, the incorporation of magnetic nanoparticles into standard scaffolds has emerged as a promising approach for tissue engineering applications. This strategy can promote not only tissue regeneration but also reloading of scaffolds through an external supervising center that adsorbs growth factors, preserving their stability and biological activity. In this study, novel magnetic silk fibroin e-gel scaffolds were prepared by the electrogelation process of concentrated Bombyx mori silk fibroin (8 wt%) aqueous solution. In addition, basic fibroblast growth factor was conjugated physically to human serum albumin = Fe3O4 nanoparticles (71.52 ± 2.3 nm in size) with 97.5% binding yield. Scanning electron microscopy images of the prepared human serum albumin = Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gel scaffolds showed a three-dimensional porous morphology. In terms of water uptake, basic fibroblast growth factor-conjugated scaffolds had the highest water absorbability among all groups. In vitro cell culture studies showed that both the human serum albumin coating of Fe3O4 nanoparticle surface and basic fibroblast growth factor conjugation had an inductive effect on cell viability. One of the most used markers of bone formation and osteoblast differentiation is alkaline phosphatase activity; human serum albumin = Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gels showed significantly enhanced alkaline phosphatase activity (p < 0.05). SaOS-2 cells cultured on human serum albumin = Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gels deposited more calcium compared with those cultured on bare silk fibroin e-gels. These results indicated that the proposed e-gel scaffolds are valuable candidates for magnetic guiding in bone tissue regeneration, and they will present new perspectives for magnetic field application in regenerative medicine.

Hydrothermal Changes of Starch Monitored by Combined NMR and DSC Methods

The thermal, dynamic, and structural properties of wheat starch–water systems with different levels of water content (11, 35, 40, 42, 45, and 50%, wet basis) were investigated. 1H time domain nuclear magnetic resonance (TD-NMR) spectroscopy was used to interpret and quantify the water transfer and starch transformations in terms of water uptake, granule swelling, amylose leaching, and melting of starch polymers in relation to the different levels of water content. Complementary differential scanning calorimetry (DSC) experiments were performed to study the effects of water content on the degree of starch gelatinization. In particular, this twofold approach was applied to the first endotherm to study the mechanisms of gelatinization with a common heating range both in NMR and DSC. It was shown that the trend of the enthalpy changes in the first phase transition in starch–water (SW) mixtures was strongly correlated with the loss of solid content measured by NMR in the corresponding temperature range (55–70 °C). Based on the evolution of the relative amplitudes of T 2, structural transformations of starch were shown to occur in both crystalline and amorphous regions within SW samples, supporting the fact that the amorphous phase of starch also plays a significant role in the phase transition of granules during gelatinization. This dynamic and hydrothermal approach provided the first NMR-based interpretation of the first endotherm measured by DSC.

A novel low cost polyvinyl alcohol-Nafion-borosilicate membrane separator for microbial fuel cell

Composite membranes were developed from PVA-borosilicate (MP) and PVA-Nafion-borosilicate (MPN) for application in microbial fuel cells (MFCs). The membranes were characterized in terms of water uptake, PBS uptake, oxygen diffusion and proton conductivity. Proton conductivity for MPN (0.07 Scm−1) was found to be higher as compared to that of MP (0.03 Scm−1). Oxygen diffusion coefficient for MPN was 1.47 fold lower than that for MP. As a result, MFC with PVA-Nafion-borosilicate membrane exhibited maximum power density of 6.8 Wm−3, which was 151% higher than the power produced by MFC having PVA-borosilicate membrane and it was comparable with MFC using Nafion 117 (7.1 Wm−3) membrane separator. This study demonstrates that borosilicate glass membrane incorporated with PVA-Nafion matrix can be a suitable alternative to costly polymeric membrane to increase power output of MFC. Using such membranes MFC can be fabricated at around 11 fold reduced cost as compared to Nafion 117.

Functionalized fullerene embedded in Nafion matrix: A modified composite membrane electrolyte for direct methanol fuel cells

Methanol permeability is a major concern for Nafion® membranes used as polymer electrolyte in direct methanol fuel cells (DMFCs). In the present study, composite membranes are formed by incorporation of functionalized fullerene (FF) in Nafion® ionomer for its use as electrolytes in direct methanol fuel cells at various methanol concentrations. Fullerene was functionalized by 4-benzene diazonium sulfonic acid precursor formed via diazotization reaction of sulfanilic acid. Surface functionalization and sulfonation of fullerene is confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and elemental analysis. Structural changes in fullerene are determined by transmission electron microscopy (TEM) analysis. The composite membranes of Nafion®-FF are prepared by solvent casting technique and characterized for their physico-chemical properties in terms of water uptake, proton conductivity and methanol permeability. The morphological changes are observed by field emission scanning electron microscopy (FE-SEM) suggesting the FF distribution in Nafion® and atomic force microscopy (AFM) explaining the presence of FF in the ionic clusters of Nafion® thereby increasing the surface roughness. Nafion®-FF composite membranes show improved proton conductivity due to the presence of surface functional –SO3H groups. Composite membranes exhibit better electrochemical selectivity and as a result enhanced DMFC power output in comparison to recast Nafion®. In addition, methanol permeability and DMFC polarization for the optimized composite membrane are carried out at different methanol concentration. The peak power density of 146mWcm−2 in DMFC is obtained for Nafion®-FF (1wt.%) at 2M methanol which is higher than the performance observed for Nafion-117. Open circuit voltage change is minimal with respect to time for Nafion®-FF (1wt.%) confirming its better stability in comparison with recast Nafion® and on par with Nafion-117.

On wettability of shale rocks

The low recovery of hydraulic fracturing fluid in unconventional shale reservoirs has been in the centre of attention from both technical and environmental perspectives in the last decade. One explanation for the loss of hydraulic fracturing fluid is fluid uptake by the shale matrix; where capillarity is the dominant process controlling this uptake. Detailed understanding of the rock wettability is thus an essential step in analysis of loss of the hydraulic fracturing fluid in shale reservoirs, especially at reservoir conditions. We therefore performed a suit of contact angle measurements on a shale sample with oil and aqueous ionic solutions, and tested the influence of different ion types (NaCl, KCl, MgCl2, CaCl2), concentrations (0.1, 0.5 and 1M), pressures (0.1, 10 and 20MPa) and temperatures (35 and 70°C). Furthermore, a physical model was developed based on the diffuse double layer theory to provide a framework for the observed experimental data.Our results show that the water contact angle for bivalent ions is larger than for monovalent ions; and that the contact angle (of both oil and different aqueous ionic solutions) increases with increase in pressure and/or temperature; these increases are more pronounced at higher ionic concentrations. Finally, the developed model correctly predicted the influence of each tested variable on contact angle. Knowing contact angle and therefore wettability, the contribution of the capillary process in terms of water uptake into shale rocks and the possible impairment of hydrocarbon production due to such uptake can be quantified.

Novel silica-functionalized aminoisophthalic acid-based membranes for base recovery via diffusion dialysis

The progress in diffusion dialysis (DD)-based separations provides an effective platform for the development of suitable materials for cation exchange membranes (CEM), as CEM-based DD processes aimed at alkali recovery have generated much interest due to their unique ion transport phenomena. Here, for the first time, we report the use of novel silica-functionalized aminoisophthalic acid (AIPA)-based CEMs with polyvinylalcohol (PVA) used as a binder for DD applications (base recovery). The synthesis of the active material AIPA involved a classic nucleophilic reaction between 5-aminoisophthalic acid and 3-glycidoxypropyltrimethoxysilane. By varying the amount of AIPA inside the membrane matrix, the properties of the prepared membranes can be altered. The prepared AIPA membranes were investigated systematically in terms of water uptake (WR), ion exchange capacity (IEC) and thermomechanical measurements, such as DMA and TGA. The influence of AIPA on the base recovery behaviour of the membranes was investigated in detail. The prepared AIPA membranes displayed water uptake values (WR) within 44.2–47.5%, ion exchange capacity (IEC) values between 0.48 and 0.93mmol/g, initial decomposition temperatures (IDTs) of 193 to 219°C, tensile strength (TS) values of 50.1 to 58.4MPa and elongation at break (Eb) values of 6.6 to 224.9%. At 25°C, the dialysis coefficient (UOH) values were between 0.0068 and 0.0097m/h, whereas the separation factors (S) ranged from 17.86 to 31.79. The membranes have great potential for base recovery via diffusion dialysis.

Differential cultivar response to chemical preservative treatment for better shelf life in Narcissus (daffodil)

Optimum level of chemical preservatives for maintaining better water relations and longevity of three different daffodil cultivars, California, Pheasants eye and Acetea was evaluated. Chemical preservatives citric acid, aluminium sulphate, silver thiosulphate and calcium chloride each at three different levels 0, 100 and 200 ppm along with carbohydrate source sucrose 4% were applied under completely randomized design. It was observed that sucrose 4%+aluminium sulphate 200 ppm helped the scape to maintain favourable water relation evaluated in terms of water uptake, water loss, water balance, fresh weight changes and improved vase life. Data available were also indicative of the fact that California outnumbered the other two cultivars in maintaining favourable water relation and longevity of cut scapes.

The influence of hair lipids in ethnic hair properties.

Biochemical studies have mainly focused on the composition of hair. African hair exhibited lower moisturization and less radial swelling when flushing with water compared with Asian or Caucasian hair, and they assumed a possible lipid differentiation among human populations. This study consists in the lipid characterization of different ethnic hairs (Caucasian, Asian and African hairs) and the influence of these lipids in different hair properties such as humidity and mechanical properties. Evaluation of water sorption and desorption of the different ethnic hairs and with and without lipids is also studied mainly to determine permeation changes of the keratin fibres. Extractions of exogenous and endogenous lipids with different organic solvents were performed; lipid analysis and its quantification using thin-layer chromatography coupled to an automated flame ionization detector (TLC/FID) were performed. Absorption and desorption curves were obtained in a thermogravimetric balance equipped with a controlled humidity chamber, the Q5000SA Sorption Analyzer (TA Instruments, New Castle, IL, U.S.A.). Also, mechanical properties (breaking stress and breaking elongation) were analysed using a computer programmable dynamometer (Instron 5500R). Lipid extraction showed the highest amount of total lipids for the African hair which may come from external sebaceous lipids compared with Asian or Caucasian hair. Caucasian fibres were found to be the most hydrated fibre, and a decrease in moisture was found in the extracted fibres, again, which is more important for the Caucasian hair. A superior lineal mass was found for the Asian fibres which supported their higher strength. The results obtained from the analysis of the mechanical properties of delipidized fibres indicate a surprising increase in the strength of African and Caucasian fibres. Perhaps this increase in strength could be related to the humidity decrease in lipid-extracted hair fibres. Results of water uptake and desorption indicate that Asian and Caucasian hairs present the lower diffusion coefficients compared with the African ones. At least for the African fibre, an extraction of its lipids that mainly account for apolar lipids ameliorates the fibre structure, decreasing its permeability to water and increasing its tensile strength. The ethnic hairs were assessed related to their lipid composition, and some differences between them were found in terms of water uptake and mechanical properties.

Size and age: intrinsic confounding factors affecting the responses to a water deficit in black spruce seedlings

Abstract: The resistance to stress of seedlings during the initial phases after planting is fundamental for assuring fast establishment and long-term survival of artificial regeneration. Although needing less storage space and handling during their production and planting, small seedlings are considered to be less efficient in terms of water uptake and more sensitive to a water deficit than bigger seedlings. The responses to a water deficit produced by a suspension of irrigation for 14 days were assessed in black spruce (Picea mariana [Mill.] BSP) seedlings of different sizes, with height ranging between 13 and 71 cm. Seedlings growing in containers with cavity volumes of 25, 50, 110, 350 cm3 were tested. During the treatment, the seedlings attained Ψpd of between -1.71 and -2.28 MPa, indicating that a severe water stress was reached. Smaller seedlings exhibited similar or higher water potential and gas exchanges than bigger seedlings both during and after the treatment. Although root biomass was higher in bigger seedlings, the growth rates of roots were similar between seedling sizes and were not affected by the water stress. The initial hypothesis that small seedlings are more sensitive to water stress was rejected. The delayed stomatal closure and higher CO2 assimilation rate of smaller seedlings during the treatment could be attributed to a lower shoot:root ratio and greater ability of roots to sustain the evaporative needs of needles, which could attain higher performances in carbon assimilation. The potential effects of confounding factors such as age and pre-treatment preventing to identify the main factor affecting drought tolerance in black spruce seedlings were discussed.

Cross-linked anion exchange membranes with pendent quaternary pyrrolidonium salts for alkaline polymer electrolyte membrane fuel cells

Novel anion-exchange membranes based on two kinds of pyrrolidonium type ionic liquids, N-methyl-N-vinyl-pyrrolidonium (NVMP) and N-ethyl-N-vinyl-pyrrolidonium (NVEP), have been synthesized via polymerization and crosslinking treatment, followed by membrane casting. The covalent cross-linked structures of these membranes are confirmed by FT-IR. The obtained membranes are also characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal, dimensional and chemical stability. The membranes display hydroxide conductivity of above 10−2 S cm−1 at 25 °C. Excellent thermal stability with onset degradation temperature above 235 °C, good alkaline stability in 6 mol L−1 NaOH at 60 °C for 168 h and remarkable dimensional stability of the resulting membranes have been proved. H2/air single fuel cells employed membrane M3 and N3 show the open-circuit voltage (OCV) of 0.953 V and 0.933 V, and the maximum power density of 88.90 mW cm−2 and 81.90 mW cm−2 at the current density of 175 mA cm−2 and 200 mA cm−2 at 65 °C, respectively.

Synthesis and performance of novel anion exchange membranes based on imidazolium ionic liquids for alkaline fuel cell applications

Novel anion exchange membranes (AEMs) based on two types of imidazolium ionic liquids, 1-vinyl-3-methylimidazolium iodide [VMI]I and 1-vinyl-3-butylimidazolium bromide [VBI]Br, have been synthesized by copolymerization. The obtained membranes are characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal and chemical stability. The conductivity reaches 0.0226 Scm−1 at 30 °C. All the membranes show excellent thermostability. The membranes are stable in 10 mol L−1 NaOH solution at 60 °C for 120 h without obvious changes in ion conductivity. Fuel cell performance using the resulting membrane has been investigated. The open circuit voltage (OCV) of the H2/O2 fuel cell is 1.07 V. A peek power density of 116 mW cm−2 is obtained at a current density of 230 mA cm−2 at 60 °C. The results demonstrate the brilliant prospect of the developed membranes for alkaline fuel cell applications.

Chitosan based micro- and nanoparticles for colon-targeted delivery of vancomycin prepared by alternative processing methods

The aim of this work was to prepare chitosan (CH) based particulate formulations for colon delivery of vancomycin (VM). Chitosan microparticles (MPs) and nanoparticles (NPs) loaded with VM were prepared using different CH/tripolyphosphate (TPP) molar ratios and different technological processes. In particular, nanoparticles were prepared by ionic gelation and freeze-drying to recover these particles, or, alternatively, by spray-drying method. Microparticles were prepared using a different spray-dryer. Micro- and nanoparticles were characterized in terms of size distributions by photon correlation spectroscopy (PCS), while encapsulation and drug loading efficiencies were studied using a dialysis method. Fourier Transform Infrared Spectroscopy (FT-IR) was employed to determine the surface composition of the micro- and nanoparticles respectively, and the morphologies of the developed systems were studied by scanning electron microscopy (SEM). Water uptake as well as drug release profiles were also measured. Antibacterial activity against Staphylococcus aureus, a Gram-positive model strain, was evaluated. FT-IR results suggested an electrostatic interaction between VM and CH/TPP particles. Moreover, the particles were found to hold a positive zeta-potential, indicating the presence of CH on the particle surfaces. Particle size and encapsulation efficiency were mainly influenced by the different manufacturing processes employed. Nanoparticles obtained by spray-drying showed the best results in terms of water uptake and drug release rate. Moreover, they showed a good bactericidal activity against S. aureus.

Performances of Sulfonated Polyether Ether Ketone Composite Membranes for Fuel Cell Applications

A variety of modification approaches such as cross-linking and nano blending have been explored to prepare efficient membranes based on Sulfonated polyether ether ketone (SPEEK). The addition filler is also one of the most widely used approaches to modify the SPEEK. The crosslinked membranes were utilized as proton exchange membranes (PEM) for fuel cell application. The performances of these composite membranes were comparative researched in terms of water uptake, ion exchange capacity, proton conductivity, and methanol permeability.While the nanohybrid membranes display remarkably enhanced proton conduction property due to the incorporation of additional sites for proton transport and the formation of well-connected channels by bridging the hydrophilic domains in SPEEK matrix. The as-prepared nanohybrid membranes also show elevated thermal and mechanical stabilities as well as decreased methanol permeability.

Study on sulphonated polysulphone/polyurethane blend membranes for fuel cell applications

The study of sulphonated polysulphone membranes (s-PSF) containing urethane groups was carried out, in order to improve the proton conductivity of a PEFC at T⩾80°C. Sulphonated polysulphone (s-PSF) polymers with a sulphonation degree (DS) ranging 40–70% were prepared following a standardised preparation procedure. An aliphatic polyurethane diol in oligomeric form (PU-Aldrich) was added to a s-PSFs with different sulphonation levels to prepare blend membranes, containing a 18%wt of PU, casting by the Doctor-Blade technique. The obtained membranes were characterised in terms of water uptake (Wup), ionic exchange capacity (IEC), swelling data, methanol permeability, scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), proton conductivity measurements and electrochemical tests in a 5cm2 commercial single cell with humidified H2/air at 80°C.By adding a 18%wt of PU, a slight increase in the IEC values respect to the pristine polymers were obtained due to a ionic crosslinking, likewise, a slight increase of Wup values was observed for each DS between pristine and corresponding blend. For all prepared samples, a lower swelling than critical value of 2 was obtained also at 100°C. PU introduction determined an enhanced proton conductivity for each DS, due to an interaction between sulphonic and nitrogenous groups caused by a possible tautomerisation mechanism. The I−V curves at 80°C confirm that blend membranes performance is higher than bare membranes, in particular, an improvement was obtained with a blend membrane containing a 18% of PU and a medium PSF sulphonation degree (48%).

PVC based polyvinyl alcohol zinc oxide composite membrane: Synthesis and electrochemical characterization for heavy metal ions

The polyvinyl chloride (PVC) based polyvinyl alcohol zinc oxide composite membrane was successfully prepared by solution casting technique. Membrane properties were studied in terms of water uptake, porosity, thickness, ion-exchange capacity and swelling. The physico-chemical characterization of the material was studied using Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. The important application of this composite ion-exchange membrane is in environmental separation of heavy metal ions transport. The increasing order of transport number of cation as HgCl2<PbCl2<CdCl2.

Effect of operating temperature on the behavior of promising SPEEK/cSMM electrolyte membrane for DMFCs

The behavior of sulfonated poly (ether ether ketone) (SPEEK) with different degrees of sulfonation (DS) (60–76%) blended with charged surface modifying macromolecule (cSMM) at different operating temperatures as an electrolyte membrane for direct methanol fuel cell (DMFC) application has been studied. A good DMFC electrolyte membrane should possess high proton conductivity and low methanol permeability. In this work, the fabricated SPEEK/cSMM membranes were compared with pure SPEEK and commercial Nafion 112 membranes in terms of water uptake, proton conductivity, and methanol permeability at temperature range of room to 80°C. The water uptake of SPEEK/cSMM membranes increased with the temperature and it was higher than that of SPEEK and Nafion 112 membranes; however newly fabricated membranes with 68% and 76% DS were dissolved at high temperatures although showed the same trend at lower temperatures. In agreement with the result of water uptake, proton conductivity of SPEEK/cSMM membranes also increased with temperature and was higher as compared to the corresponding SPEEK membranes; however it was still lower than that of Nafion 112. The methanol permeability values of the SPEEK/cSMM membranes were lower at different temperatures as compared to corresponding SPEEK and Nafion 112 at the same condition. Owing to considerable proton conductivity and lower methanol permeability values, SPEEK60/cSMM exhibited the highest overall performance than other tested membranes at 60°C. These results indicated that SPEEK60/cSMM membrane is promising to be used as a polymer electrolyte membrane in direct methanol fuel cell.

Chitosan/bioactive glass nanoparticle composite membranes for periodontal regeneration

Barrier membranes are used in periodontal applications with the aim of supporting periodontal regeneration by physically blocking migration of epithelial cells. The present work proposes a combination of chitosan (CHT) with bioactive glass nanoparticles (BG-NPs) in order to produce a novel guided tissue and bone regeneration membrane, fabricated by solvent casting. The CHT/BG-NP nanocomposite membranes are characterized in terms of water uptake, in mechanical tests, under simulated physiological conditions and in in vitro bioactivity tests. The addition of BG-NPs to CHT membranes decreased the mechanical potential of these membranes, but on the other hand the bioactivity improved. The membranes containing the BG-NPs induced the precipitation of bone-like apatite in simulated body fluid (SBF). Biological tests were carried out using human periodontal ligament cells and human bone marrow stromal cells. CHT/BG-NP composite membranes promoted cell metabolic activity and mineralization. The results indicate that the CHT/BG-NP composite membrane could potentially be used as a temporary guided tissue regeneration membrane in periodontal regeneration, with the possibility to induce bone regeneration.

Accelerated hydrothermal aging of epoxy resin based syntactic foams with polymeric microspheres

Insulation systems have to interact with their environment. In outdoor applications they have to withstand atmospheric stress such as temperature and humidity. This leads to aging processes inside the insulation material and results in a change of material properties and consequently can lead to a failure of the high voltage component. Hence, knowledge about the aging behavior of syntactic foam is essential for its use in outdoor applications. Syntactic foam is a composite material consisting of a polymer matrix and hollow microspheres. This study focuses on the hydrothermal aging of epoxy resin based syntactic foam with polymeric microspheres. The aim of this study is to benchmark the use of syntactic foam in outdoor applications. The impact of different microspheres' diameters, filling degrees and additional silica particles on the aging process is presented. The aging behavior is investigated for different syntactic foam compositions for two aging methods - the climatic chamber and the pressure cooker storage. To evaluate the aging process of the material the mass, the dielectric constant and the breakdown voltage is monitored over several aging times in the climatic chamber and the pressure cooker, respectively. The parameter study shows very good hydrothermal aging behavior of syntactic foam in terms of water uptake and the development of the dielectric constant over the aging time. The use of small microspheres improves the breakdown voltage after the aging process significantly and features similar relative breakdown voltages as conventional silica filled epoxy compositions.

Study of in vitro degradation of biodegradable polymer based thin films and tissue engineering scaffolds

This paper reports the in vitro degradation of three-dimensional, highly porous tissue engineering scaffolds and non-porous thin films based on poly (L-lactide) (PLLA) biopolymers. The tissue engineering scaffolds were produced through the emulsion freezing/freeze-drying technique. The nonporous thin films were produced using solvent casting technique. In vitro degradation experiments in terms of water uptake, water diffusion and weight loss were performed for various period of time. Results show that the scaffolds had more water uptake than the thin films at the same experimental condition. After 6 weeks, the weight loss of scaffolds was much greater than the films.