Lower Water Diffusion Research Articles

Evaluation of glymphatic system activity by diffusion tensor image analysis along the perivascular space (DTI-ALPS) in dementia patients.

Dementia is a clinical syndrome caused by multiple etiologies, usually manifests with progressive and diffuse brain dysfunction. The activity of the human glymphatic system was evaluated in cases of dementia by the diffusion tensor image analysis along the perivascular space (DTI-ALPS). We recruited 28 healthy subjects and 77 patients, including 38 with Alzheimer's disease (AD),18 with mild cognitive impairment (MCI), 28 with normal controls (NC) and 21 with vascular cognitive impairment (VCI). All participants underwent DTI scanning. Diffusivities in the X, Y and Z axes were obtained in the lateral ventricle body plane of all subjects. We assessed the diffusivity along the perivascular spaces, as well as projection fibers and association fibers, respectively, in order to acquire an DTI-ALPS-index and correlated them with mini mental state examination (MMSE) and montreal cognitive assessment (MOCA) scores using partial correlation which the influence of age was controlled. The AD, MCI, and VCI patients showed significantly lower DTI-ALPS-index (p < 0.001) compared to the NC. Besides, the VCI group had significantly higher DTI-ALPS-index than the AD group (p = 0.007). There was a significant positive correlation between DTI-ALPS-index and MMSE and MOCA scores (the effect of age was controlled), showing that lower water diffusivity along the perivascular spaces associated with dementia.The higher Dzassoc led to the reduced DTI-ALPS-index in VCI, while lower Dxassoc contributed to the decrease of DTI-ALPS-index in AD. The evaluation of DTI-ALPS demonstrates impairment of the glymphatic system in dementia patients by decreased DTI-ALPS-index. Different from AD, the VCI patients show glymphatic drainage disorder rather than glymphatic system impairment. This article comprehensively covers several types of dementia and performs the comparison of VCI, AD and MCI in glymphatic system dysfunction.

Towards the influences of three types of biocrusts on soil water in drylands: Insights from horizontal infiltration and soil water retention

As a “living skin” of soil in drylands, biocrusts possibly change the retention and movement of soil water, and thus critically influence hydrological and erosion processes as well as soil moisture regime. Contrary to vertical infiltration, little attention was paid to horizontal infiltration, which may provide important information on soil water diffusivity and sorptivity. In this study, the one-dimensional horizontal infiltration experiments for bare soil and three types of biocrusts (cyanobacterial, cyanobacterial-moss mixed, and moss crusts) were conducted with disturbed soil samples in a semiarid dryland. Undisturbed soil samples were also taken for each treatment, and their soil water retention capacity were determined in the laboratory. The substantial differences that were found were analyzed, and the differences were further validated through monitoring and comparing their in situ soil moisture regimes at depth of 0–20 cm. Our results showed that the three types of biocrusts had significantly lower constant infiltration rate (0.11 vs. 0.18 cm min−1) and infiltration water amount (6.75 vs. 10.01 cm) than bare soil, and their wetting front moved much slower (0.60 vs. 1.14 cm min−1) in comparison to bare soil, with bare soil > cyanobacterial crusts > cyanobacterial-moss mixed crusts > moss crusts. Total sorptivity of cyanobacterial, mixed, and moss crusts were 21%, 32%, and 53% lower than that of bare soil, respectively. More importantly, at the same level of water content, all crust types had lower water diffusivity, sorptivity, and conductivity than the bare soil, and exhibited a higher water content than bare soil at a same level of matric potential (across the range of −15,000–0 hPa), indicating an increase in water-holding capacity and water availability of the biocrusts in contrast to bare soil. Furthermore, the in-situ soil water content of all biocrusts increased on average by 30% at depth of 0–10 cm but decreased by 23% at 10–20 cm. Confirming the lower infiltrability and higher water-holding capacity of the biocrusts in comparison to bare soil, biocrusts increase surface soil water retention capacity and water availability at the surface, thus playing a vital role in reshaping the surface soil water balance, which subsequently may affect surface hydropedological and biochemical processes in drylands.

Shape-controlled fabrication of cost-effective, scalable and anti-biofouling hydrogel foams for solar-powered clean water production

• Development of closed-cell hydrogel foams via a controlled foaming − gelation technique. • Demonstration of self-contained solar evaporation and desalination. • Realization of a single-stage water purifier for efficient clean water production. Solar-powered interfacial evaporation has emerged as a sustainable technology for clean water production with a minimized carbon footprint. Fabrication of three-dimensional (3D) steam generators via conventional processing techniques (sol–gel and template-assisted methods) remain one of the main roadblocks toward mass production and scalable applications. In this study, 3D hydrogel foams based on biopolymer composites are developed via a controlled foaming − gelation technique and applied to a monolithic interfacial steam generator. The designed closed-cell structures deliver many important form-factors to the hydrogel foams, such as light-weight, low-cost, low thermal insulation and efficient water diffusion. The hydrogel foam with a maximum height of 3.2 cm attains a high water evaporation rate of 2.12 kg m −2 h −1 and a high cost-effectiveness of 2692 g h −1 $ −1 under one sun. A single-stage water purification system is fabricated based on the high-performing hydrogel foam. Because of its self-floating structure and enhanced passive cooling on open water, the system attains a maximum clean water collection rate of 0.71 L m −2 h −1 under real sky and surpasses a majority of single-stage solar stills. This work demonstrates the rational fabrication of hydrogel foams and combines high-performance solar evaporation with other intriguing properties (i.e., cost-efficient, scalable, anti-biofouling, self-floating and anti-overturning). The system-level design enables facile scale-up of clean water production.

Water absorption and hydrothermal ageing of epoxy adhesives reinforced with amino-functionalized graphene oxide nanoparticles

The study is focused on quantitative characterization of water absorption and hydrothermal ageing effects in a room-temperature amine cured epoxy adhesive widely used in automotive, aerospace, construction, and marine industries. Amino-functionalized graphene oxide (mGO) nanoparticles were incorporated into the epoxy (up to 1.72 wt.%) enabled cross-linking reactions and providing high interfacial adhesion, superior reinforcement efficiency and enhanced resistance to hydrothermal ageing of nanocomposites. Anomalous water absorption accompanied by progressive weight loss of samples (down to 7%) is fitted by two-stage models considering additive and coupled contribution from water diffusion and leaching of low molecular weight epoxy species. Nanocomposites are characterized by lower water diffusivity (40%) and decreased leaching effects (70%). High reinforcing efficiency of epoxy/mGO appeared in the increased glassy and rubbery storage moduli (60%), glass transition temperature (10 °C) and activation energy of glass transition (70%) compared to the neat epoxy. Hydrothermal ageing resulted in noticeable properties degradation of samples, although to a much lower extent in the case of nanocomposites. The results will contribute to the enhancement of global durability of common epoxy-based adhesives and extension of their lifetime.

Evaluation of Glymphatic System Using Diffusion MR Technique in T2DM Cases.

Objective: We aimed to evaluate the activity of the human glymphatic system in type 2 diabetes mellitus (T2DM) using diffusion tensor image analysis along with the perivascular space (DTI-ALPS).Methods: Diffusion tensor images were acquired to calculate the diffusivities in the direction of the x-axis (right-to-left; Dx), y-axis (anterior-to-posterior; Dy), and z-axis (inferior-to-superior; Dz) of the plane of the lateral ventricle body in 20 patients with type 2 diabetes and 10 people in a control group. We evaluated the diffusivity along with the perivascular spaces, as well as the projection fibers and association fibers, separately. The analysis along the perivascular space (ALPS-index) was defined as the mean (Dxpro, Dypro)/mean (Dypro, Dzasc), where the Dxpro and Dxasc were the Dx values in the projection and association fiber areas, respectively.Results: There were significant differences in diffusivity along the projection fibers and the association fibers among the groups. The significant differences among the groups along the perivascular spaces, shown as the ALPS-index and medical history of T2DM, indicating lower water diffusivity along the perivascular space concerning type 2 diabetes severity, was also observed.Conclusion: Lower diffusivity along the perivascular space on DTI-APLS can reflect impairment of the glymphatic system in T2DM. This study showed that the activity of the glymphatic system could be evaluated by diffusion tensor image analysis.

Impact of sugar beet seed priming using the SMP method on the properties of the pericarp

BackgroundThis study determined the effects of two solid matrix priming methods on changes in the characteristics of two lots of the same variety of sugar beet fruits that differ in the level of vigour.ResultsSeed treatment within each level of vigour did not significantly affect helium and apparent density, total pore volume and total porosity. However, there was a tendency to increase porosity due to priming. This is probably why seed priming significantly increased mesopore diameter in both high and low vigour seeds. These changes increased the water content in the pericarp and the seeds and increased the water potential during germination. The high level of electrical conductivity of the fruit extracts was associated with low seed vigour. Low vigour resulted in higher humidity of the pericarp and decreased seed moisture and was also associated with lower water potential of the pericarp and seeds.ConclusionsA significant difference in the water content in the pericarp and seeds was indicative of imbibition and problems with water flow between these centres, which resulted in a low water diffusion coefficient of the pericarp. This low water diffusion coefficient was correlated with the prolongation of the seed germination time.

Mechanical properties and water absorption characteristics of composites reinforced with cotton fibres recovered from textile waste

The primary aim of this research is to develop thermoset composites reinforced with cotton fibres extracted from textile waste. These composites are mainly targeted to replace timber in its application for furniture items and in some visible and non-visible automotive components. The pre-consumer cotton textile wastes such as cutting waste, in garment manufacturing, and defective fabrics were converted into the fibrous form called ‘shoddy’, using rag-tearing technique. The fibrous web of shoddy was produced using the carding machine. This web was used for developing thermoset composites as a reinforcement material. The thermoset composites with four different fibre volume fraction values, namely 0.1, 0.2, 0.3 and 0.4 were developed using compression moulding technique. The developed composites were characterised by mechanical properties, dynamic mechanical properties, thermal degradation behaviour and water absorption behaviour. The mechanical properties of the composites were found comparable with that of commercial wood. These composites can be used to develop a dashboard panel. The composites developed in this research have shown low water diffusion coefficient values as compared with pine, oak and linden wood.

Composites based on Juncus maritimus fibers for building insulation

Juncus maritimus fibers present an interesting cellular porous microstructure useful for thermal insulating properties. The elaboration and experimental characterization of composite materials based on different Juncus maritimus fibers content (0, 2, 5, 7 and 10 by mass) are investigated. We show that optimized composite materials can be elaborated from a simple chemically treatment of fibers. The thermo-physical properties (thermal conductivity, thermal diffusivity, and density) of both mortar composites with the raw and chemically treated fibers, were evaluated experimentally. Also, the water absorption uptake and mechanical strengths were performed to evaluate the chemical surface modification effects on the performances of the composites. As a result, due to their porous cellular microstructure, the use of Juncus maritimus fibers enhances the thermal insulating and lightness performances of reference mortar but affects negatively its mechanical strengths. The moisture effect tests reveal that thermal conductivity and density of the saturated composites are two times higher than that in a dry state. The chemical surface modification of used Juncus maritimus fibers improves the flexural and compressive strengths, decreases the water uptake of resulting composites with a low water diffusion coefficient. Thus, these new treated bio-cellular fibers composites can be used as structural and insulating lightweight concrete.

Water permeation and corrosion resistance of single- and two-component hydrophobic polysiloxane barrier coatings

The degradation of corrosion preventative coatings contributes to the high cost and time requirements for maintaining structures in harsh environments. However, the development of new hydrophobic coatings holds the promise of extending the usable life of structures in marine environments. In this work, we quantify the barrier properties and corrosion resistance of two novel highly hydrophobic polysiloxane formulations and the legacy silicone alkyd topcoat used on the topside of Navy’s ships, all with haze gray pigmentation. Based on FTIR-ATR and EIS measurements of the pristine coatings, both the single- (1K) and the two-component (2K) polysiloxane provide significantly improved barrier characteristics (lower water diffusion coefficient and capacitance) than the silicone alkyd. These results were confirmed through a 3-month-long immersion corrosion test, which also showed that the 1K and 2K polysiloxane coatings had comparable degradation characteristic and remained highly hydrophobic.

Evaluation of glymphatic system activity with the diffusion MR technique: diffusion tensor image analysis along the perivascular space (DTI-ALPS) in Alzheimer's disease cases.

The activity of the glymphatic system is impaired in animal models of Alzheimer's disease (AD). We evaluated the activity of the human glymphatic system in cases of AD with a diffusion-based technique called diffusion tensor image analysis along the perivascular space (DTI-ALPS). Diffusion tensor images were acquired to calculate diffusivities in the x, y, and z axes of the plane of the lateral ventricle body in 31 patients. We evaluated the diffusivity along the perivascular spaces as well as projection fibers and association fibers separately, to acquire an index for diffusivity along the perivascular space (ALPS-index) and correlated them with the mini mental state examinations (MMSE) score. We found a significant negative correlation between diffusivity along the projection fibers and association fibers. We also observed a significant positive correlation between diffusivity along perivascular spaces shown as ALPS-index and the MMSE score, indicating lower water diffusivity along the perivascular space in relation to AD severity. Activity of the glymphatic system may be evaluated with diffusion images. Lower diffusivity along the perivascular space on DTI-APLS seems to reflect impairment of the glymphatic system. This method may be useful for evaluating the activity of the glymphatic system.

Hydrophobic networks for advanced proton conducting membrane: Synthesis, transport properties and chemical stability

The design of interpenetrated networks (IPN) membranes for fuel cell applications requires both an electrolyte and a neutral network. The composition and architecture of the latter are of major importance for the final IPN membrane properties. In this work, networks based on a fluorinated diepoxy oligomer (DFODDE) and a non-fluorinated triepoxy monomer (TMPTGE) were synthesized. The network composition was varied from 100% DFODDE to 100% TMPTGE, resulting in an increase of the crosslinking density and concomitantly a decrease of the fluorine content. The curing process was optimized to achieve a total epoxy conversion and the chemical structure of the networks was characterized by Raman and Infrared spectroscopies. The physical, thermal and chemical membrane properties were studied and discussed as a function of the crosslinking density and of the fluorine content. Increasing the crosslinking density led to a decrease of the membrane permeability to oxygen. Water sorption properties depended on both parameters, with a prevailing role of the fluorine content on the water uptake and a major influence of the crosslinking density on the diffusion parameter. The thermal stability increased also with the fluorine content. All materials exhibited a good stability in water at 80°C but a significant weight loss after immersion in a concentrated H2O2 solution. Altogether, these results indicate that networks containing 20% of TMPTGE exhibit an interesting set of properties (low oxygen permeability, high Tg, good chemical and thermal stability) to behave as a neutral partner in an IPN membrane. Moreover, the low water uptake and diffusion rate measured in these networks make them attractive for water barrier membranes.

Ionic Liquid Containing Solid Polymer Electrolytes for Lithium Metal Batteries

Researching novel battery systems is essential for the turn away from fossil fuels and electrification of cars, since renewable energies (e.g. light, wind) are not available at all times and the energy is not necessarily consumed at the place where it is gained. Lithium air / lithium oxygen batteries state a possible candidate facing the necessity for high energy battery systems, due to a high theoretical energy density (11.680 Wh∙kg-1), comparable with those of gasoline (13.000 Wh∙kg-1).[1] Several reasons hindered the commercialization of secondary lithium air / lithium oxygen batteries so far. On the cathode side the oxygen evolution and the oxygen reduction reaction are not yet efficient without (expensive) catalysts (e.g. gold, platinum). Like in normal lithium metal batteries, most of the challenges are related to the negative electrode material. Lithium metal is unstable against various materials, including the commonly used organic carbonate based electrolytes. While reacting with the electrolyte, the capacity of the battery is dramatically fading, and a highly resistive layer, the Solid Electrolyte Interface (SEI) is growing. The reaction of electrode and electrolyte does not only lead to solid components, but also to gaseous products, which in closed systems cause dangerous pressure increase. Within a lithium air battery also reactions with other components of the ambient air (e.g. carbon dioxide, nitrogen, moisture) have to be taken into account. During these reactions inactive materials like lithium carbonate and -nitrate are formed, disabling the cyclability very fast. The most important reason hindering the commercialization of secondary lithium metal batteries is the formation of high surface area lithium during cycling, categorized by the morphology subdivided into dendritic, mossy and granular lithium. Dendritic lithium is the most dangerous one. The best case scenario would be a loss of contact of the dendrites to the lithium metal electrode, just leading to a fade in capacity. The worst case would be a dendrite growing through the separator to the positive electrode, causing thermal runaway and explosion of the cell. This can be prevented by the use of a solid electrolyte. Solid electrolytes have negligible vapor pressure, are not flammable and are leakage-free. They also combine the benefits of a separator with an electrolyte, thus saving costs. Depending on the system they have low gas and water diffusion rates. One drawback compared to liquid electrolytes is the usually much lower specific conductivity. Within the last years ionic liquids have been investigated, and they show a suppression of dendrite growth.[2] They have higher specific conductivities than solid electrolytes, but still there are some drawbacks in open systems (e.g. in lithium air batteries) like leakage and cost. Solid polymer- and gel electrolytes offer good compromises. In this work we show the combnation of a solid polymer electrolyte with an ionic liquid, combining the benefits of both systems. We will introduce tetrafluoroborate based Solid Polymer Electrolytes (SPEs). Compared to systems based on trifluoromethylsulfonylimide,[3] they combine good conductivity in the desired temperature region (20-60 °C) with high electrochemical stability, while tetrafluoroborateas anion offers water stability and is cheap in production. Free standing films with thicknesses of 80 - 100 µm were achieved (Figure 1), while keeping the mechanical properties needed for handcrafted cell building. The SPEs were characterized in respect to their electrochemical behavior in lithium metal half cells (plating/stripping), conductivities (electrochemical impedance spectroscopy - Figure 2) as well as electrochemical stability (linear sweep voltammetry) and compared to our previous prepared bis(oxalate)borate based SPEs.[4] Also lithium metal full cells (Lithium vs. Lithium iron phosphate) were tested (cyclic voltammetry - Figure 3). The tests were carried out temperature dependent. [1] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, W. Wilcke, J. Phys. Chem. Lett., 1, (2010), 2193-2203. [2] G.B. Appetecci, G.T. Kim, M. Montanino, M. Carewska, R. Marcilla, D. Mecerreyes, I. De Meatza, J. Power Sources, 195, (2010), 3668-3675. [3] G.T. Kim, G.B. Appetecci, M. Carewska, M. Joost, A. Balducci, M. Winter, S. Passerini, J. Power Sources, 195,(2010), 6130-6137. [4] R. Jakelski, M. Winter, P. Bieker, Conference Poster No. 508, 224th ECS, (2013). Figure 1

Abstract 734: Water diffusion decreased in low collagen containing hypoxic regions of breast cancer xenograft.

Abstract Tumors display chaotic vasculature that leads to hypoxia. Hypoxia is associated with an aggressive phenotype and increased resistance to radiation and chemotherapy. Hypoxic tumor regions also contain very few collagen 1 fibers, which is a major component of the tumor extracellular matrix (ECM) and plays an important role in molecular movement through the ECM. Here we examined the effects of hypoxia on water diffusion in a breast cancer xenograft model engineered to fluoresce under hypoxia. We observed, for the first time, that in hypoxic regions water diffusion and diffusion anisotropy was lower than in normoxic regions that may be explained by the few collagen fibers in hypoxic regions. Severe combined immunodeficient female mice were inoculated in the mammary fat pad with 2x106 MDA-MB-231 cells stably expressing red fluorescent protein (RFP) under the control of a hypoxia response element. Once tumor volume was approximately 300-400 mm3 the tumor was excised, fixed and imaged using high-resolution diffusion tensor imaging (DTI). The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps were calculated. Following DTI, the tumor was sliced at 1 mm thick sections for optical imaging. Using a 1x lens to cover the entire tumor section, bright field and fluorescence optical images were acquired to detect the RFP-containing hypoxic regions. Multimodality registration was performed by feature extraction to co-register the optical images to the DTI images. Statistical dice similarity indices were calculated as a measure of the registration error. Hypoxic regions were identified from the optical fluorescence field images and the ADC and FA values were calculated in the corresponding hypoxic and normoxic regions. ADC and FA value distributions were identified in the DTI data and red fluorescent hypoxic regions were identified from the optical images. Co-registration accuracy confirmed by dice similarity index of 0.88 indicates a good overlap of optical and DTI images. Overall, hypoxic regions had lower water diffusion (ADC) and diffusion anisotropy (FA) values than normoxic regions. We have consistently observed that collagen fibers are significantly decreased in hypoxic regions, which could explain the lower ADC and FA values observed in hypoxic regions. In separate studies we have also observed high ADC in high collagen fiber containing regions in human breast cancer tissue. Low ADC and FA values observed in low collagen containing hypoxic regions indicate a functional role of these fibers in molecular transport. Decreased diffusion of molecules due to fewer collagen fibers in hypoxic regions may also contribute to poor drug delivery and tumor recurrence in hypoxic regions. Increased cellularity is thought to be one reason why lower ADC and FA values are observed in tumors. An even lower ADC within this backdrop may be due to hypoxic tumor regions. This work was supported by NIH P50CA103175 P30CA006973 Citation Format: Samata M. Kakkad, Jiangyang Zhang, Alireza Akhbardeh, Meiyappan Solaiyappan, Venu Raman, Dieter Leibfritz, Kristine Glunde, Zaver M. Bhujwalla. Water diffusion decreased in low collagen containing hypoxic regions of breast cancer xenograft. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 734. doi:10.1158/1538-7445.AM2013-734

Modulation of the Structures and Properties of Bacterial Cellulose Film by Fermentation Carbon Sources

Bacterial cellulose (BC), a natural pure cellulose synthesized by some bacteria, shows great potentials for wound dressing applications. In order to obtain suitable properties, different fermentation carbon sources, i.e. glucose, maltose and sucrose were used to synthesize BC films by static culture. The crystallinity and pore analysis was performed by X-ray diffraction spectroscopy and nitrogen physisorption measurements, respectively. Some important properties of BC materials from different carbon sources were investigated, such as the mechanical strength, water holding capacity, water swelling ratio and water diffusion ability, which were key parameters for wound dressing applications. For comparison, the conventional cotton fiber was used as control. It was found that the carbon sources could change both the structures and properties of BC. The sucrose-derived BC exhibited lower crystallinity, but more suitable mechanical property, higher water holding capacity and water swelling ratio than other samples. All tested BC samples showed higher water holding capacity and water swelling ratio, but lower water diffusion property than the cotton fibers which were expected as good wound-healing biomedical materials.

Moisture Permeation in Liquid Crystalline Epoxy Thermosets

AbstractA liquid crystalline thermoset (LCT), 4,4′‐diglycidyloxy‐α‐methylstilbene/sulfanilamide, is studied by dynamic mechanical and vapor sorption measurements. Sub‐Tg transitions are assigned to the specific segmental motions through molecular modeling and used to define the environmental temperatures for the study of water transport properties in LCT. The variation of moisture transport with amine‐epoxy ratio reveals that the crosslink density and local concentration of polar groups play the key role in determining both the diffusivity and solubility. The LCT exhibits much lower water diffusion than analogous isotropic networks while the solubility is essentially the same. Segmental flexibility and an ordered smectic layered structure are responsible for the lower permeability.

The effect of the side-chain ratio on main-chain-type and side-chain-type sulfonated poly(ether ether ketone) for direct methanol fuel cell applications

A series of side-chain ratios of novel main-chain-type and side-chain-type sulfonated poly(ether ether ketone)s (MS-SPEEKs) were synthesised by reaction of the sulfonic acid groups of pristine SPEEKs with 2-aminoethanesulfonic acid to improve the nano-phase separated morphology of the material. 1H NMR and FT-IR spectroscopy was employed to determine the structure and composition of main-chain-type and side-chain-type sulfonated polymers. Flexible and tough membranes with reasonable thermal properties were obtained. The MS-SPEEKs showed good hydrolytic stability, and water uptake values that range from 17% to 25% were observed. Compared to Nafion® 117, the methanol permeability of the MS-SPEEKs was dramatically reduced to between 9.97 × 10−8 cm2 s−1 and 1.51 × 10−7 cm2 s−1. The proton conductivity increased with increasing temperature and reached 0.031–0.099 S cm−1. A maximum power density and open-circuit voltage of 142 mW cm−2 and 0.79 V, respectively, were obtained at 70 °C, which were significantly greater than the values generated with Nafion® 117. The introduction of pendent side-chain-type sulfonic acid groups with a side-chain ratio of 8% showed the best cell performance; thus, the lower water diffusivity, lower methanol permeability and higher cell performance indicated that MS-SPEEK was a promising candidate for DMFC applications.

Preparation of main-chain-type and side-chain-type sulfonated poly(ether ether ketone) membranes for direct methanol fuel cell applications

Novel main-chain-type and side-chain-type sulphonated poly(ether ether ketone)s (MS-SPEEKs) are synthesised by reacting the sulphonic acid groups of pristine SPEEKs with 2-aminoethanesulphonic acid to improve the nano-phase separated morphology of the material. 1H NMR and FT-IR spectroscopy are employed to determine the structure and composition of main-chain-type and side-chain-type sulphonated polymers. Flexible and tough membranes with reasonable thermal properties are obtained. The MS-SPEEKs show good hydrolytic stability, and water uptake values ranging from 15% to 30% are observed. Compared to Nafion 117 ®, the methanol permeability of the MS-SPEEKs is dramatically reduced to 8.83 × 10 −8 cm 2 s −1 to 3.31 × 10 −7 cm 2 s −1. The proton conductivity increases with increasing temperature, reaching 0.013–0.182 S cm −1. A maximum power density and open circuit voltage of 115 mW cm −2 and 0.830 V are obtained at 80 °C, respectively, which is significantly greater than the values generated with Nafion 117 ®. The introduction of pendent side-chain-type sulphonic acid groups increases the single-cell performance by more than approximately 20%; thus, the lower water diffusivity, methanol permeability, electro-osmotic drag coefficient and high cell performance indicated that MS-SPEEK is a promising candidate for DMFC applications.

Jute fiber reinforced polypropylene produced by continuous extrusion compounding, part 1: Processing and ageing properties

AbstractThis article addresses the processing and ageing properties of jute fiber reinforced polypropylene (PP) composites. The composite has been manufactured by a continuous extrusion process and results in free flowing composite granules, comprising up to 50 weight percent (wt %) jute fiber in PP. These granules have similar shape and diameter as commercially available PP granules. Rheological analysis shows that viscosity of the compounds follows the same shear rate dependency as PP and is on the same level as glass‐PP compounds. The mechanical properties show very little variation and exhibit strength and stiffness values at the upper range of competing natural fiber reinforced compounds for injection molding. The mechanical performance reduces gradually upon prolonged thermal loading and immersion in water. The low water diffusion coefficient of the 50 wt % jute‐PP composites indicates that the fibers are not forming a continuous network throughout the polymer. The jute fibers exhibit a stabilizing effect against ultra violet irradiation (UV) on PP polymer and, as a consequence, the mechanical properties of jute‐PP composites hardly decrease during an accelerated UV ageing test. Bacteria, fungi, and garden mold grow easily on the compound material, but only have a limited effect on mechanical properties. The resistance to growth of bacteria on the materials surface can be increased using a biostabilizer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Water diffusion into silica glass at a low temperature under high water vapor pressure

Water in glass has disproportionately large effects on various properties of oxide glasses, such as chemical durability and mechanical strength. Silica glass is the basis of many oxide glasses. Thus, there have been numerous studies on water diffusion into silica glasses. But most past research on water diffusion into silica glasses has been conducted at high temperatures, where water diffusion is accompanied by structural changes of the glass. In the present study, water diffusion into silica glass at low temperature, 250°C, was measured using IR spectroscopy as the main research tool. Saturated high water vapor pressure was used to increase the amount of water diffusing into the glass so that the water can be detected by the IR method after a reasonably short heat-treatment time. It was found that both water solubility and diffusion coefficient were time dependent. Furthermore, both hydroxyl and molecular water were detected in the glass. From the concentrations of hydroxyl and molecular water, an apparent equilibrium constant, K=[SiOH]n/[H2O] was evaluated. At high temperatures, water reacts with silica glass by Si–O–Si+H2O↔2SiOH, and the local reaction equilibrium has been established at the value of n being 2. In the present study of low temperature water diffusion in silica glass, unlike the local reaction equilibrium in high temperature studies, the value of n was found to be close to 1. This indicates that the two hydroxyls formed in the glass during the reaction are not independent of each other.

EFFECTS OF GLASS MICROFILLERS ON THE WATER-TRANSPORT BEHAVIOR OF POLYURETHANE COMPOSITES

Glass microspheres with unique composition and diameter, and modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the liquid transport properties of the PU composites. Transport properties such as diffusion, permeability, and sorption coefficient were measured on various filler-filled PU composites at three different temperatures. These temperature-dependent parameters were used to provide a quantitative way to examine the effects of filler loading and the surface properties on the improvement of the water transport properties of PU composites. Results show that due to trapping at interfacial boundaries between filler and polymer, a high water affinity and large space for water activity is expected inside all the filler-filled composites. As a result, lower water diffusion (or high water resistivity) was found among all the filler-filled composites compared to that of filler-free composites. Besides, the more filler present in the composite, the longer the paths of the water molecules within the composites as the water penetration proceeds. Thus, lower diffusion coefficient values were observed for composites with large amounts of filler addition.