Decrease In Water Uptake Research Articles

Surface properties of thermally treated composite wood panels

Composite finger-jointed spruce and oak wood panels have been thermally treated under standard pressure and oxygen content conditions at two different temperatures, 180°C and respectively 200°C for short time periods (3 and 5h). Due to the thermally-aided chemical restructuration of the wood components, a decrease in water uptake and volumetric swelling values with up to 45% for spruce and 35% for oak have been registered, comparing to the reference samples. In relation to water resistance, a 15% increase of the dispersive component of the surface energy has been registered for the thermal-treated spruce panels, which impedes water spreading on the surface. The thermal-treated wood presents superior resistance to accelerated UV exposure and subsequently, with up to 10% higher Brinell hardness values than reference wood. The proposed thermal treatment improves the durability of the finger-jointed wood through a more economically and environmental friendly method than traditional impregnation, with minimal degradative impact on the structural components of wood.

Mechanical and moisture absorption characterization of PLA composites reinforced with nano-coated flax fibers

This research is intended to improve the interface between the fibers and the matrix and limit water absorption of bio-based material thereby decreasing degradation of the composites when they are exposed to external environment such as high temperature and humidity. In this study, flax fibers were treated with an organic surface coating containing SiO2 nanoparticles. This coating was a dispersion of silica fume in epoxy. One composite was also made with raw fibers as reference as well as one sample of pure PLA. Flax fibers/PLA composites were manufactured by hot pressing by stacking 4 PLA films and 3 pieces of flax fabric. Morphology and dispersion of the coating on the fibers was observed by scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Accelerated ageing was carried out on the 3 materials by placing them in a 50 °C water bath until saturation to investigate the influence of the coating on water diffusion. Mechanical properties of the different composites were investigated by tensile (before and after conditioning) and short beam shear (SBS) testing in order to evaluate the impact of the coating on the interfacial properties of the materials. The results show that the fibers surface was homogenized and that a better adhesion was reached because of the coating. Coating the fibers also allowed the decrease in water uptake by more than 10 % and their protection during conditioning, preserving their mechanical properties.

Exploring backbone-cation alkyl spacers for multi-cation side chain anion exchange membranes

In order to systematically study how the arrangement of cations on the side chain and length of alkyl spacers between cations impact the performance of multi-cation AEMs for alkaline fuel cells, a series of polyphenylene oxide (PPO)-based AEMs with different cationic side chains were synthesized. This work resulted in samples with two or three cations in a side chain pendant to the PPO backbone. More importantly, the length of the spacer between cations varied from 3 methylene (-CH2-) (C3) groups to 8 methylene (C8) groups. The highest conductivity, up to 99 mS/cm in liquid water at room temperature, was observed for the triple-cation side chain AEM with pentyl (C5) or hexyl (C6) spacers. The multi-cation AEMs were found to have decreased water uptake and ionic conductivity when the spacer chains between cations were lengthened from pentyl (C5) or hexyl (C6) to octyl (C8) linking groups. The triple-cation membranes with pentyl (C5) or hexyl (C6) groups between cations showed greatest stability after immersion in 1 M NaOH at 80 °C for 500 h.

Effect of polymer sulfonation on the proton conductivity and fuel cell performance of polyvinylalcohol‐mordenite direct methanol fuel cell membranes

AbstractSulfonated polyvinylalcohol‐mordenite (SPVA‐MOR) membranes for direct methanol fuel cell use were synthesized and characterized. It had earlier been found out that polyvinylalcohol‐mordenite (PVA‐MOR) membranes, while having excellent methanol permeability and modest proton conductivity values, had inferior direct methanol fuel cell performances than Nafion™. Sulfonating the polyvinylalcohol matrix had been suggested to improve the proton conductivity. In this work, polyvinylalcohol powder was sulfonated by using propane sultone as the sulfonating agent prior to the membrane synthesis. Morphological analyses revealed that the zeolite particles mixed homogeneously within the polymer matrix. Sulfonating the polymer slightly decreased both water and methanol uptakes. Both in PVA‐MOR and SPVA‐MOR membranes, water uptake turned out to be higher than the methanol uptake. SPVA‐MOR membranes were found to have an average proton conductivity of 0.052 S·cm−1 when compared with the 0.036 S·cm−1 of PVA‐MOR membranes, while Nafion™ has a proton conductivity of approximately 0.1 S·cm−1. The increase in the proton conductivity upon sulfonation despite the decrease in water uptake was explained by the dominance of the Grotthuss mechanism over the vehicular mechanism for proton conductivity. Fuel cell test results showed that while SPVA‐MOR membranes cannot outperform Nafion™, they give higher power output than PVA‐MOR membranes, especially at low temperatures and high methanol concentrations. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Investigation of the temperature dependence of water adsorption on silica-based stationary phases in hydrophilic interaction liquid chromatography

In the present work, the adsorption of water was investigated in aqueous normal-phase liquid chromatography on Cogent Silica C and Cogent Phenyl hydride stationary phases at different temperatures by frontal analysis – using coulometric Karl Fischer titration – to compare the temperature dependence of adsorption of water from aqueous acetonitrile.The Cogent Silica-C and Cogent Phenyl Hydride columns have a silicon hydride surface (silica hydride) with less than 2% free silanol group; therefore, they do not have a strong association with water. The adsorption behavior of water on the mentioned stationary phases was modeled by Langmuir isotherm. The preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water slightly depends on the temperature.The adsorbed water may fill four to eight percent of the pore volume over the studied temperature range, which approximately corresponds to the equivalent of 0.24–0.68 water layer coverage of the adsorbent surface. The phenyl hydride stationary phase shows decreased water uptake in comparison to the Silica C stationary phase.

Nanopartículas de sílica silanizada como compatibilizante em compósitos de fibras de sisal/polietileno

Resumo Foi discutida neste estudo a influência de nanopartículas de sílica na compatibilidade entre fibras de sisal e polietileno de alta densidade, utilizados na preparação de compósitos. As fibras de sisal foram tratadas quimicamente e recobertas com nanopartículas de sílica por moagem mecânica. Os compósitos foram preparados por extrusão do polietileno com diferentes quantidades de fibras. Utilizou-se diferentes técnicas de caracterização para se obter as propriedades térmicas e a morfologia das fibras de sisal e dos compósitos, a influência das fibras de sisal e da sílica na cristalinidade do polietileno e o comportamento mecânico e a absorção de água do polietileno e dos compósitos. Foi observado que a as propriedades térmicas do polietileno não são afetadas pela presença das fibras e nanopartículas. Os diferentes tratamentos químicos e a presença de sílica nas fibras de sisal resultaram em propriedades mecânicas melhoradas e foram preponderantes para a diminuição da absorção de água nos compósitos, comparados ao polietileno.

Insight into halloysite nanotubes-loaded gellan gum hydrogels for soft tissue engineering applications

A tri-component hydrogel, based on gellan gum (GG), glycerol (Gly) and halloysite nanotubes (HNT), is proposed in this work for soft tissue engineering applications. The FDA-approved GG polysaccharide has been recently exploited as biomaterial because its biomimetic features. Gly is added as molecular spacer to improve hydrogel viscosity and mechanical properties. HNT incorporation within the hydrogel offers the versatility to improve the GG-Gly biocompatibility with potential incorporation of target biomolecules. In this work, hydrogels with different composition ratios are physically crosslinked for tuning physico-mechanical properties. An accurate physico-chemical characterization is reported. HNT addition leads to a water uptake decrease of 30–35% and tuneable mechanical properties with a compressive Young’s modulus ranging between 20 and 75kPa. Finally, in vitro study with human fibroblasts on GG-Gly hydrogels loaded with 25% HNT offered the higher metabolic activities and cell survival up to 7days of incubation.

Groundwater Level Changes since 1978 in an African City on Basement Rocks: The Case of the CIEH Borehole in Ouagadougou (Burkina Faso)

The CIEH piezometer, located in the center of Ouagadougou city presents a water level record spanning the West African Drought which peaked during the 80s and 90s. Its water level is investigated as a potential proxy for groundwater water resources in West African basement rock aquifers submitted to climate changes. 23 boreholes and wells in various land uses and within a 2 km radius around the CIEH piezometer were monitored during the 2013-2014 hydrologic year. The minimum water level occurred in May, at the end of the dry season, while the maximum took place in October, one month after the end of the rainy season. The mean water level amplitude is 3 m, the minimum amplitude being reached at the CIEH piezometer (0.76 m). Moreover, the CIEH piezometer is located in a 2 m amplitude water table depression either in May or in October. Simplified 2d modeling using a general basement aquifer structure shows that (i) the water level in the piezometer is under ongoing influence of the spillway raise of the nearby dam#3 lake in 2002, (ii) the whole 1978-2004 period cannot be modelled with constant parameters. A 3% decrease of water uptake is adopted after 1985, presumably resulting from land use changes in the Ouagadougou city. The water table at the CIEH piezometer is presently at its 1978 level, which can considered as a pre-drought value. However this includes a 1.5 m contribution of the two abovementioned anthropic effects Further quantitative interpretations of the CIEH piezometer record will require additional geophysical and hydrological investigations.

Synthesis and Characterization of Stable Anion Exchange Membranes: The Addition of Electron-withdrawing Group

Anion exchange membranes (AEM) based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were used as polymer electrolyte membrane for fuel cell applications. The membranes were prepared via bromination, quaternization and nitration reactions and their fuel cell-related properties (water uptake, ion exchange capacity, ionic conductivity) were determined. Also, the structures and thermal properties were studied with Fourier transform infrared spectroscopy (FTIR), Size exclusion chromatography (SEC) and Differential scanning calorimetry (DSC). Nitration of quaternized PPO (Q-PPO) leaded to a decrease in water uptake and ion exchange capacity of the AEM. However, Q-PPO membrane treated with nitration reaction (NO 2 -Q-PPO) exhibited a significant alkaline stability compared to quaternized PPO (Q-PPO). The results indicated that the addition of electron-withdrawing group, such as nitro, into the structure in order to improve in alkaline stability is a promising new route for preparation alkaline stable AEM membranes.

GISAXS Analysis for Ionomer Thin Films

Perfluorinated sulfonic-acid (PFSA) polymers are a class of ion-conducting polymers (ionomers) heavily utilized in fuel cells and similar electrochemical technologies. The hydrophobic backbone gives excellent mechanical properties, while the side-chain terminated with a hydrophilic acid group bestows superior proton conductivity. The crystallinity of the backbone is believed to be inversely proportional to conductivity and proportional to the mechanical modulus in bulk membranes. Demonstrated previously, the transport and mechanical properties of PFSA ionomers deviate from bulk membranes as the ionomers are confined into thin-film geometries.[1]Under such confinement, conductivity and water uptake decrease, while the modulus increases. Studying this deviation from bulk behavior is crucial as ionomer is present as thin films in the catalyst layer of these electrochemical devices. In this work, we correlate the relative crystallinity of PFSA thin-films, calculated from Grazing-incidence Wide-angle X-ray Scattering (GIWAXS), to their mechanical properties measured using a cantilever bending system.[2]Using a laser array, thin-film stress can be measured as a function of humidity from which mechanical properties are calculated. This system allows the study of thin films on hard impenetrable surfaces that induce confinement effects, and probe the effect of interfacial interactions on different substrates. Understanding crystallinity and mechanical properties as part of the structure-property relationship will allow optimization of ionomer performance within the catalyst layer. Acknowledgement This work was sponsored by the Army Research Office under MIPR0010754069. The work utilizes beamline 7.3.3 at the Advanced Light Source, which is funded by DOE Basic Energy Science under contract number DE-AC02-05CH11231.

Side Chain Influence on the Mechanical Properties and Water Uptake of Confined Comb-Shaped Cationic Polymer Thin Films

Water uptake is measured for ≈100 nm and ≈60 μm thick quaternized comb-shaped poly(2,6-dimethyl-1,4-phenylene oxide) (QA-PPO) polymers with 0, 6, 10, and 16 carbon alkyl side chains to probe the influence of thin film confinement. The thin film modulus is measured to probe the effect of side chain length on the thin film modulus and the ensuing water uptake. Increasing the alkyl side chain length results in increased modulus, decreased swelling strain, and decreased water uptake due to the lengthening of the n-alkyl side chains. Confinement effects on the comb-shaped QA-PPO water uptake are expressed through increased water uptake in the thin film compared to the bulk membrane. The thin films also exhibit a different water sorption mechanism consistent with two types of water compared to the bulk membranes that exhibit a single type of water sorption.

Polymer Electrolyte Composite Membrane Based on Molecular Sieve 13X Mixed with Sulfonated Poly(ether ketone ether sulfone)/Poly(phenylene ether ether sulfone) Blended Membrane for Use in Direct Methanol Fuel Cell

AbstractBlend membranes between sulfonated poly(ether ketone ether sulfone) (S‐PEKES) and poly(phenylene ether ether sulfone) (PPEES) were fabricated at various mole ratios. Interestingly, increasing the hydrophobic PPEES in S‐PEKES/PPEES blend membranes led to the decreases in water uptake (%) when compared to S‐PEKES. Incorporation of molecular sieve 13X drastically improved proton conductivity. Methanol permeability slightly decreased with molecular sieve 13X. The composite membrane with the 15% v/v molecular sieve 13X content showed the highest proton conductivity of 1.44 × 10−2 S/cm which is four times higher than Nafion 117. Thus, the blending between S‐PEKES and PPEES can help to decrease methanol permeability, and incorporating molecular sieve 13X can enhance proton conductivity.

Study to extend the vase life of cut rose (Rosa hybrida L.) flowers

This study investigated anatomic and physiologic changes during senescence to improve the vase life of cut rose flowers. When holding the flowers in the distilled water, the fresh weight increased in the 2nd day, and decreased in the following days. In progressing flower senescence, there were decreases in water uptake, dry weight, rate of photosynthesis, and concentration of auxin, gibberellin and zeatin, while the ionic conductance, and ABA concentration increased. The rate of respiration increased until the 3rd day, and then decreased. The UV absorption curve of the petal extract showed two peaks at 446 and 665 nm. The absorbances was the highest in the 1st day then decreased in the following days. Among the treatments, the combination of 10 mg/L BA, 1 mg/L GA3 and 0.1 mg/L NAA, and the combination of 10 mg/L BA and 0.1 mg/L NAA gave a vase life for cut roses 2 days longer than that of the control.

Effect of neem wood sawdust content on properties of biodegradable thermoplastic acetylated cassava starch/neem wood sawdust composites

Due to several important limitations for applications of thermoplastic starch (TPS), thermoplastic acetylated cassava starch (TPACS) polymer was reinforced by different contents of neem wood sawdust (SD). Thermoplastic cassava starch (TPCS)/SD composites were also prepared and reinforced by different SD contents and compared with the TPACS/SD composites. Morphological, thermal, and biodegradable properties of different composites were also examined. The results showed that IR absorption bands of OH stretching and OH bending vibrations shifted to lower wavenumbers, indicating new hydrogen bond formation for all composites. Stress at maximum load and Young's modulus were significantly improved when the SD content increased for all the TPACS/SD and TPCS/SD composites; strain at maximum load was higher for the TPACS/SD composites. A decrease in water uptake was detected when the SD reinforcement was incorporated into either the TPACS or TPCS matrix.

Effects of salt stress on eco-physiological characteristics in Robinia pseudoacacia based on salt-soil rhizosphere

Robinia pseudoacacia is the main arbor species in the coastal saline–alkali area of the Yellow River Delta. Because most studies focus on the aboveground parts, detailed information regarding root functioning under salinity is scare. Root traits of seedlings of R. pseudoacacia including morphological, physiological and growth properties under four salinity levels (CK, 1‰, 3‰ and 5‰ NaCl) were studied by the pot experiments to better understand their functions and relationships with the shoots. The results showed that seedling biomass decreased by the reduction of root, stem and leaf biomass with the increase of salinity levels. With increasing salinity levels, total root length (TRL) and total root surface area (TRSA) decreased, whereas specific root length (SRL) and specific root area (SRA) increased. Salt stress decreased root activity (RA) and the maximum net photosynthetic rate (Amax) and increased the water saturation deficit (WSD) significantly in the body. Correlation analyses showed significantly correlations between root morphological and physiological parameters and seedling biomass and shoot physiological indexes. R. pseudoacacia seedlings could adapt to 1‰ salinity by regulating the root morphology and physiology, but failed in 5‰ salinity. How to adjust the water status in the body with decreasing water uptake by roots was an important way for R. pseudoacacia seedlings to adapt to the salt stress.

Processing–properties–applications relationship of nanocomposites based on thermoplastic corn starch and talc

Films based on thermoplastic corn starch (TPS) and talc nanoparticles were developed by melt mixing and thermo‐compression. Films structure, optical and barrier properties, as well as thermal stability and water sorption behavior were studied. TPS structure resulted homogeneous and smooth. Talc laminar morphology and thermo‐compression induced particle preferential orientation within the matrix. Good particle distribution and talc‐TPS adhesion were evidenced. Nanometric thickness of mineral particles allowed obtaining translucent composite films, without significant color variation of TPS films. Talc addition at concentrations higher than 3% w/w led to an improvement on TPS barrier properties against water vapor and oxygen. It was also demonstrated that talc decreased water uptake of TPS films exposed to ambient conditions with relative humidity higher than 40%. In conclusion, films based on TPS and talc nanoparticles could be an alternative to develop biodegradable packages for food products with suitable final properties. POLYM. COMPOS., 39:1331–1338, 2018. © 2016 Society of Plastics Engineers

Soft-matrices based on silk fibroin and alginate for tissue engineering

Soft tissue regeneration requires the use of matrices that exhibit adequate mechanical properties as well as the ability to supply nutrients and oxygen, and to remove metabolic bio-products. In this work, we describe the development of hydrogels based on the blend between alginate (Alg) and silk fibroin (SF). Herein, we report two main strategies to combine cells with biomaterials: cells are either seeded onto prefabricated hydrogels films (2D), or encapsulated during hydrogel microcapsules formation (3D). Both geometries were successfully produced and characterized. FTIR results indicated a change of conformation of SF from random coil to β-sheet after hydrogel formation. The thermal degradation behavior of films and microcapsules fabricated from Alg, and Alg/SF was dependent on the hydrogel composition and on the geometry of the samples. The presence of SF caused decreased water uptake ability and affected the degradation behavior. Mechanical tests showed that addition of SF promotes an increase in storage modulus, leading to a stiffer material as compared with pure Alg (6 times higher stiffness). Moreover, the in vitro cell-material interaction on Alg/SF hydrogels of different geometries was investigated using human umbilical vein endothelial cells (HUVECs). Viability, attachment, spreading and proliferation of HUVECs were significantly increased on Alg/SF hydrogels compared to neat Alg. These findings indicate that Alg/SF hydrogel is a promising material for the biomedical applications in tissue-engineering and regeneration.

Indirect monitoring of root activity in soybean cultivars under contrasting moisture regimes by measuring electrical capacitance

The applicability of root electrical capacitance (EC) measurement for in situ investigation of root activity and drought tolerance was tested in soybean cultivars. Well-watered and drought-stressed plants were grown in pots with repeated EC measurements, followed terminally by harvest to determine root dry mass (RDM), shoot dry mass (SDM), root/shoot ratio (RSR) and leaf area (LA). EC measurement showed the cultivar differences in root growth and biomass production. EC increased till the beginning of flowering, then became nearly constant. Terminal EC was highly correlated with RDM for non-stressed (R 2 = 0.844) and stressed plants (R 2 = 0.936). Drought reduced the EC of cultivars by 28.8–50.5 %, consistently with the corresponding changes of SDM (25.5–49.1 %) and LA (23.6–51.5 %), but considerably exceeded the loss of RDM (12.6–47.3 %) in some cultivars. The reason is drought increased the RSR (by 3.9–21.9 %), leading to decreased water uptake, and thus EC per unit of RDM. This was confirmed by the significantly decreased slope of EC–RDM regression line from 0.437 to 0.317 nF g−1 RDM calculated for well-watered and drought-stressed plants, respectively. As EC referred to root uptake activity, it was better indicator of the actual root status than RDM. EC measurement was adequate for monitoring the cultivar-specific differences in root growth and for estimation of biomass loss caused by drought. By supplementing the conventional methods, this in situ technique could be useful for various fields of agriculture, including cultivar selection or stress tolerance studies.

Plant water relations and canopy temperature depression for assessing water stress tolerance of potato

An experiment was conducted with five potato genotypes at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during 2010–2011 under control and water stress conditions to determine the effect of water stress on plant water relations and canopy temperature depression of potato. Of the five genotypes, CIP 393371.58 and CIP 396244.12 maintained higher relative water content (RWC) under both the conditions and showed comparatively less midday depression in RWC. The water stress condition significantly decreased water uptake capacity. Under water stress condition tolerant genotypes CIP 393371.58 and CIP 396244.12 showed highest xylem exudation rate of 0.26 and 0.18 g h−1, respectively and transpiration rate of 36 and 34 µg m−2 s−1, respectively at 50 days after planting, and both were positively and significantly correlated. Greater increases in canopy temperature were observed at noon in Asterix and CIP 391004.18 and lower in CIP 393371.58 and CIP 396244.12 and showed inverse relationship with transpiration rate. The genotypes CIP 393371.58 and CIP 396244.12 showed higher canopy temperature depression value and the genotypes CIP 391004.18 and Asterix showed lower canopy temperature depression value under water stress condition. Among the genotypes, CIP 393371.58 and CIP 396244.12 showed better tolerance to water stress condition.

Effect of reinforced Al2O3 nanoparticles on collagen nanobiocomposite from chrome-containing leather waste for biomedical applications

The present study aims at developing nanobiocomposite from collagen extracted from solid biowaste, chrome-containing leather waste having aluminium oxide nanoparticles as reinforcement for value-added products. The extracted collagen was confirmed using sodium dodecyl sulphate-poly(acrylamide) gel electrophoresis technique, while Fourier-transform infrared spectroscopy and scanning electron microscopy were used to study the physicochemical and morphological properties of the prepared composites. Enhanced thermal stability and increase in denaturation temperature from 39 to 43 °C with the increase in aluminium oxide content from 2 to 10 % in the composites were confirmed by differential scanning calorimetry and thermogravimetric analyses. Improved mechanical properties such as tensile, tear and flexural strength for the nanobiocomposites (NBCs) were also obtained. Moreover, decrease in water uptake from 475 to 285 % with the increase in aluminium oxide nanoparticles is attributed to the reduced porosity and their weak interaction with collagen that reduces the hydrophilicity of the NBCs. The above results indicate that the collagen-based NBCs present a simple, clean and easy route for effective recycling and recovery of biowaste that could find use in hip prosthesis and has the potential to be used in other biomedical applications.