Influence Of Water Uptake Research Articles

Relative Humidity Dependence of Growth Factor and Real Refractive Index for Sea Salt/Malonic Acid Internally Mixed Aerosols

AbstractSea salt aerosols (SSAs) often mix with organic matter via sea‐to‐air emission, photochemical oxidation, and atmospheric transport, which change particle hygroscopicity and real refractive index (RRI), thereby the radiative effects. However, the influence of water uptake and organic matters on radiative effects is not well understood. In this study, relative humidity (RH)‐dependent growth factor (GF), light scattering enhancement factor, RRI (nmea), and radiative forcing efficiency (RFE) in the visible spectrum of SSAs/malonic acid (MA) internally mixed aerosols were investigated. Our results showed that MA‐mediated SSAs readily absorbed water even at low RH but suppressed hygroscopic growth at high RH. The discrepancy between Zdanovskii‐Stokes‐Robinson predictions and measured GF indicated that the suppressing effect on size caused by produced malonate salts in chloride depletion became more evident as MA content increased. RRI in the visible spectrum decreased as MA got enriched and approached toward water's RRI at high RH, resulting in a less cooling effect. The increasing RH reduced RFE both by decreasing RRI and increasing particle size substantially. Ignoring the effect of MA on particle size and RRI under varied RH, errors in RFE at 525 nm up to 25% could be induced. Volume mixing rule performs well in predicting the RRI of mixed aerosols in dry conditions, while the retrieved difference of 0.061 between volume mixing RRI nvol and nmea would make the error in RFE up to 1.15 W·m−2·Aerosol optical depth−1 at 87% RH. Our study helps understand the impact of water content and dicarboxylic acids on the direct radiative effects of SSAs.

Water transport in epoxy/polyurethane interpenetrating networks

AbstractDiffusion of water in epoxy–polyurethane (PU) interpenetrating networks was investigated using gravimetry, time‐resolved ATR‐FTIR, and 2D correlation analysis. In this study, the amount of PU component and the length of polyethylene oxide soft block in them were systematically varied to determine their influence on water uptake. The diffusion coefficients were calculated and anomalous water diffusion is well described by the Carter and Kibler model. Water molecules of four different states were identified in the network volume, and sequence of their formation was determined by 2D‐IR spectroscopy. One of them could be confined into free volume (microvoids) or molecularly dispersed with hydrogen‐bonding at cluster formation (bulk dissolved), while the others could be attributed to the bound water forming strong hydrogen bonds with hydrophilic entities of networks. These results were supported by solid‐state 2H NMR data. The influence of water uptake on thermomechanical behavior of epoxy/PU networks was determined. It was shown that the increase of PU content in composites leads to the changes of the effect of water uptake from plasticizing to the anti‐plasticizing as a result of the formation of new networks of interchain hydrogen bonds.

Investigation of the effect of water absorption on thermomechanical and viscoelastic properties of flax‐hemp‐reinforced hybrid composite

AbstractThe recent development of natural fiber‐reinforced polymer composites have shown innumerable economic and environmental benefits for a vast array of engineering applications. It is quintessential to investigate the effect of water absorption on the composites that remain in the water for a maximum of their intended service period. This study is an effort in this direction that investigates the effect of water absorption on thermo‐mechanical properties of flax‐hemp‐reinforced epoxy composites fabricated using compression hand layup technique with different weight fraction of fiber. The fabricated composites have been characterized physically (density and water absorption), thermo‐mechanically (tensile, flexural, thermal conductivity, and dynamical mechanical analysis), and morphologically (scanning electron microscopy [SEM]). The analysis revealed that hemp‐reinforced composites (S1) had the highest water absorption capabilities in comparison to the flax‐reinforced composites (S5). Higher water absorption capability had an adverse effect on the mechanical properties of fabricated composites. However, hybrid composites (S2, S3, and S4) reported better performance with regard to S1. The increased water content, however, increased the thermal conductivity of composites and maximum has been revealed for S1 (0.82 W/mK) and minimum for S5 (0.48 W/mK). The water molecules showed detrimental effects on the viscoelastic properties and revealed S3 have better interlocking bond with the lowest reduction in storage modulus (12%) and glass transition temperature (4°C) in comparison to S1 (30%) under wet conditions. A comparative analysis of the thermo‐mechanical properties was also made for developed composites under dry, saturated, and re‐dried conditions. The SEM has been used to characterize the morphological and fracture behavior of the fabricated composites under the influence of water uptake. The effects of water molecules on the hygrothermal aging index and diffusion co‐efficient have also been discussed. Overall, the hybridization of flax with hemp fiber showed better results over the hemp fiber‐reinforced composites (S1).

Influence of Water Uptake, Charge, Manning Parameter, and Contact Angle on Water and Salt Transport in Commercial Ion Exchange Membranes

In electrochemical processes such as electrodialysis or redox flow batteries, where ion exchange membranes (IEMs) play a critical role in process performance, energy losses can be reduced by minimi...

The Effect of Moisture on the Properties of Glass Fiber Polymer Matrix Composites with MoS2 and CaCO3

The mechanical properties and water absorption behavior of a pure glass fiber reinforced epoxy matrix and a glass fiber reinforced epoxy filled composites immersed into a tap water were investigated. The main purpose of this experiment is addition of two different powdered fillers (CaCO3 and MoS2) into the epoxy matrix and comparing the properties of pure GFRP and filled GFRP. The composites specimens with fillers absorb less water when compared to pure GFRP specimens at room temperature. Water absorption curves and equilibrium moisture content were determined. The composites exhibit a positive deviation from the Fickan’s law with the addition of fillers into the matrix. The influence of water uptake has significant effect on the reduction of mechanical properties. It is observed that 3% filled MoS2 in epoxy matrix has less uptake of water and the tensile strength decreased is 3% , flexural strength decreased up to 18% and shear strength is 42% decreased when compared to CaCO3 filled composites and unfilled glass fiber reinforced polymer composite.

Effect of hydration on water state, glass transition dynamics and crystalline structure in chitosan films

The influence of water uptake on water state, glass transition dynamics and crystalline structure in chitosan films was investigated by differential scanning calorimetry (DSC), X-ray diffraction and infrared spectroscopy (FTIR) techniques. DSC result indicated that two types of water, i.e., non-freezable water and freezable water, appeared in turn with the gradual increase of water content. Only the non-freezable water was responsible for the reduction of glass transition temperature (Tg), which leveled off at higher hydration levels. Structural analysis revealed that moisture could bring about a slight increase in the crystallinity of polymer due to alignment of hydrated and relaxed chitosan chains in the amorphous region. FTIR result showed that the hydrogen bonds and electrostatic forces existing in chitosan films varied slightly with water content. These observations suggest that changing the water content in such systems offers the possibility to control the microstructure as well as properties of polymers.

Influence of water uptake on the electrical DC-conductivity of insulating LDPE/MgO nanocomposites

Low-density polyethylene (LDPE), typically in cross-linked form, is currently the main insulation material for extruded high voltage cables. The DC-conductivity of LDPE can be reduced 100 times by adding 1–3 wt% well-dispersed metal-oxide nanoparticles (MgO, ZnO, Al2O3), but the underlying physics remain unclear. One of several feasible explanations is that the nanoparticles attract electrical charges, polar molecules (H2O and crosslinking by-products) and ions (H+, OH−, salts and ionic species originating from the crosslinking by-products), and thus clean the polymer. Effective media FEM simulations, assuming that the polymer conductivity is proportional to the moisture content, were used in order to examine this hypothesis. Water sorption measurements for LDPE and MgO/LDPE nanocomposites were conducted as experimental input. The simulations could conceptually predict the experimentally measured composite conductivities. The hypothesis was further strengthened by DC-conductivity measurements on LDPE and MgO/LDPE nanocomposites at 0 and 50% relative humidity (RH), showing a 100-fold conductivity increase for the nanocomposite at the elevated humidity. The DC-conductivity of the most insulating composite (3 wt% MgO) was below 10−16 S/m after 64 h at 60 °C and 0% RH, using an electric field of ca 30 kV/mm. The long-term insulation efficiency of an insulating polymer nanocomposite is thus optimal if the material is carefully dried and surrounded by an impenetrable moisture barrier before use.

Influence of atmospheric water uptake on the hydrolysis of stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate

Abstract In this paper we report on the influence of water uptake on the hydrolysis of anhydrous stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py 1,4 ]TfO) under ambient atmosphere. The effect of water uptake on the electrodeposition of tin in the employed ionic liquid containing 0.1 M SnCl 2 was also demonstrated. The hydrolysis products as well as the Sn electrodeposits were characterized by different techniques comprising; scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results show that the employed ionic liquid electrolyte strongly absorbs water under ambient conditions. Colloidal particles were formed in the electrolyte after an exposure time of about 4 weeks as a result of the hydrolysis of Sn(II) species. The electrochemical behaviour of the employed electrolyte and the morphology of tin electrodeposits were significantly influenced by the presence of water. Tin dendrites were obtained from IL-electrolyte exposed to air for one month, whereas dendrite free deposits were formed in the freshly prepared electrolyte.

Frost durability of steel fiber self-compacting concrete for pavements

The paper presents the results from the research on self-compacting concrete with different steel fibre type addition. The reference self-compacting concrete mix with water/binder = 0.33 was prepared, then modified with steel fibres in the amounts of 0–60 kg/m3 and air entrained with polymer microspheres (40 μm diameter). The major objective of the research was to determine the effect of steel fibre and air content on the self-compacting concrete mix properties and hardened concrete frost durability. The tests also included internal cracking and scaling resistance evaluation for concrete specimens subjected to cyclic freeze-thaw process − two beams were frozen in air and two beams were partially submerged in water and then frozen. The scaling resistance was tested using the slab method on the specimens with sawn surface and on the specimens with natural finished surface. Non-air entrained steel fibrereinforced concretes, despite their high strength class (C55/67–C60/75) and medium absorption (4.34–5.11%), showed unsatisfactory resistance to internal cracking and scaling tests. The beams partially submerged in water failed after 100 freeze-thaw cycles, which confirms a significant influence of water uptake from moist environment during freeze-thaw cycles and the acceleration of the damage process. Test results indicate that air entrainment with polymer microspheres is a very effective method and allows obtaining very good air pore structure parameters and frost resistance results. The specimens with top − finished surface exhibited less damage in the scaling resistance tests in relation to the specimens with sawn surface.

The influence of water uptake on matric head variability in a drip-irrigated root zone

Irrigation is a service provided to agricultural crops in order to improve their yields. This is also a rare situation where the location of the costumers (roots) is not known and the heterogeneity in the water delivery system (soil) effects the water distribution. This non-uniformity of soil-plant conditions in the agricultural field complicates decision-making parameters regarding irrigation management (where to place sensors, how many sensors are needed, when and how much to irrigate). Many aspects of this non-uniformity have been studied in the past decades, including soil hydraulic properties, tillage history, irrigation method, sensor location, measured volume, and more. One aspect that has been relatively neglected is how plant roots affect variability. In this work, we focus on the effect that growing roots have on the variability of tensiometer measurements.Corn seeds were sown in a pre-designed experimental plot that consisted of three very distinct soils (sand, sandy loam, clay) to create high variation in investigated conditions. Subsurface drip irrigation was installed in the plot, and the drippers of the center line were wrapped with geotextile to create a geotextile-drip interface (GDI), i.e., a volume which has preferred conditions for root growth. Tensiometers were installed in the GDI (GDI treatment) and 10cm away from the drip lines (S10 treatment); the matric head was monitored throughout the season.The weekly averaged coefficient of variation (CV) of the GDI treatment decreased as the corn plants grew, for each soil type and the entire plot. As time passed and the corn plants grew, CV peaks, due to irrigation, and the duration of high CV decreased because of the increasing influence of root water uptake on fluxes in the measured volume. After harvest, the CV returned to initial values. S10 tensiometers showed higher CV values than the GDI tensiometers during the last week of growth. After harvest, the CV of the S10 tensiometer measurements decreased, contrary to the trend in the GDI tensiometers. The results point to the major influence of roots on matric head variability, first, by decreasing variability with time and second, through the effect of tensiometer location since the GDI tensiometers were located in volumes with high root density. This influence has major consequences regarding the methodology of tensiometer measurements to represent an agricultural field, and might provide means for global guidelines for tensiometer placement and irrigation management.

Influence of Water Uptake on Dynamic Fracture Behavior of Poly(Methyl Methacrylate)

A study was completed to assess the effects of various humidity levels and amount of sorbed water on the fracture behavior of notched poly(methyl methacrylate) (PMMA) samples subjected to stress pulses generated by the impact of a projectile launched from an air gun. Impact experiments were performed on six sets of samples conditioned in different environments: dry samples; samples exposed to three different relative humidity environments (11 %, 60 %, and 98 %) using saturated salt solutions (Lithium Chloride, Sodium Bromide, and Potassium Sulfate, respectively); and distilled water- and seawater-exposed samples. Experiments varied by immersion time and water content, while loading conditions were kept constant. The main goal of this study was to understand the effects of sorbed water on the fracture behavior of PMMA when subjected to high strain rate impacts. It was observed that when PMMA is subjected to strain rates of 102 s −1, the effect of water content is not a dominant mechanism on the crack initiation and crack-tip speed of PMMA.

A study on the mechanical properties and the influence of water uptake and temperature on biocomposites based on polyethylene from renewable sources

This work is aimed to evaluate the properties in terms of structural applications of the fully biobased composites obtained at reasonable price, without additional and costly chemical modifications. The bio-polyethylene obtained from sugarcane ethanol (Braskem, Brazil) was filled with four different fillers (25wt.%): wood flour, ultrafine cellulose powder, kenaf chopped fibres and microparticles of mineral tuff filler. Physical, mechanical and thermal properties of the biocomposites were tested, as well as the influence of soaking in water and temperature on tensile properties. The fracture surfaces were studied using scanning electron microscope. Low density, increase in stiffness, improved resistance to deformation on heat and thermal properties stabilization within the temperatures of usage were the main advantages of the biocomposites comparing to the neat biopolyethylene.

Environmental effects on the mechanical behaviour of pultruded jute/glass fibre-reinforced polyester hybrid composites

The environmental degradation of the mechanical properties of pultruded jute and jute/glass hybrid reinforced polyester composites with high fibre volume fraction (0.70) has been investigated with special focus on the effects of water ageing and moderate temperature (up to 80 °C). Water absorption tests were conducted by immersing specimens in distilled water at room temperature until saturation (4076 h). Water absorption curves and characteristic parameters such as coefficient of diffusion and equilibrium moisture content were determined. The composites exhibited a deviation from the Fickian behaviour with a positive role played by the addition of glass fibres in terms of moisture resistance. The influence of water uptake on tensile and flexural properties of composites was evaluated and a significant reduction in both strength and modulus was observed, with a superior strength retention offered by hybrid composites. Acoustic emission (AE) and scanning electron microscopy enabled to identify the weakening of fibre/matrix interface induced by water ageing. The effects of temperature were mitigated by glass fibres if compared with the higher degradation experienced by jute fibres.

Influence of water uptake on the aerosol particle light scattering coefficients of the Central European aerosol

The influence of aerosol water uptake on the aerosol particle light scattering was examined at the regional continental research site Melpitz, Germany. The scattering enhancement factor f(RH), defined as the aerosol particle scattering coefficient at a certain relative humidity (RH) divided by its dry value, was measured using a humidified nephelometer. The chemical composition and other microphysical properties were measured in parallel. f(RH) showed a strong variation, e.g. with values between 1.2 and 3.6 at RH=85% and λ=550 nm. The chemical composition was found to be the main factor determining the magnitude of f(RH), since the magnitude of f(RH) clearly correlated with the inorganic mass fraction measured by an aerosol mass spectrometer (AMS). Hysteresis within the recorded humidograms was observed and explained by long-range transported sea salt. A closure study using Mie theory showed the consistency of the measured parameters.

Potential of using polyester reinforced coconut fiber composites derived from recycling polyethylene terephthalate (PET) waste

Unsaturated polyester resin synthesized from glycolyzed product of polyethylene terephthalate (PET) waste was used as a matrix to form coconut fiber/polyester composites. PET wastes were recycled through glycolysis and polyesterification reaction to produce a formulation for unsaturated polyester resin (UPR). FTIR spectra of glycolyzed product and prepared resin revealed that cross-links between unsaturated polyester chain and styrene monomer occurred at the saturated sites which resulted in the forming of cross linking network. To improve the adhesion between coconut fiber and polyester resin, various concentrations of alkali, silane and silane on alkalized fiber were applied and the optimum concentration of treatments was determined. The influence of water uptake on the sorption characteristics of composites was studied via immersion in distilled water at room temperature. Surface treatment of coconut fiber caused a significant increase in the tensile properties with the optimum treatment is 0.5 % silane on the 5 % alkalized coconut fiber/polyester composites. It was also observed that the treated fiber composites showed lower water absorption properties in comparison to those of untreated fiber composites. This observation was well supported by the SEM investigations of the fracture surfaces. From the study, it was concluded that polyester reinforced coconut fiber composites derived from recycling polyethylene terephthalate (PET) waste may have the potential application in the fields of construction and automotive interior substrates.

Effect of Chemical Treatment on Mechanical and Water-Sorption Properties Coconut Fiber-Unsaturated Polyester from Recycled PET

Coconut fibers were used as reinforcement for unsaturated polyester resin from recycled PET that has been prepared using glycolysis and polyesterification reaction. Various concentrations of alkali, silane, and silane on alkalized fiber were applied and the optimum concentration of treatments was determined. Morphological and mechanical properties of the composite have also been investigated to study the effect of fiber surface treatment. The influence of water uptake on the sorption characteristics of composites was studied via immersion in distilled water at room temperature. Surface treatment of coconut fiber caused a significant increase in the tensile properties with the optimum treatment of 0.5% silane on the 5% alkalized coconut fiber/polyester composites. For water absorption study, it was observed that the treated fiber composites showed lower water absorption properties in comparison to those of untreated fiber composites. SEM investigation showed that the surface modification of fiber has better fiber-matrix interaction. Thus, chemical treatments on the fiber improve fiber/matrix adhesion especially for silane on alkalized fiber treatment.

Influence of water uptake, gel network, and disintegration time on prednisone release from encapsulated solid dispersions

Prednisone is considered the glucocorticoid of choice for anti-inflammatory and immunosuppressant effects. However, its very low aqueous solubility can compromise oral bioavailability. Changes in the dissolution of a prednisone-PEG 6000 solid dispersion into capsule were investigated by addition of pregelatinized starch. Physical state of prednisone:PEG 6000 was analyzed by X-ray diffractometry, and scanning electron microscopy. Capsule formulations containing prednisone-PEG 6000 and pregelatinized starch showed superior dissolution properties (> 95% in 60 min) when compared with reference capsules without disintegrant (< 45% in 60 min). Water uptake and disintegration time were directly correlated with pregelatinized starch amount. The morphology of prednisone-PEG 6000 particles with disintegrant was analyzed by SEM, showing a novel surface structure. Thus, solid dispersions of a poorly water soluble drug combined with a disintegrant were confirmed as a valid approach to the improvement of drug dissolution.

Influence of water uptake, gel network, and disintegration time on prednisone release from encapsulated solid dispersions

Prednisone is considered the glucocorticoid of choice for anti-inflammatory and immunosuppressant effects. However, its very low aqueous solubility can compromise oral bioavailability. Changes in the dissolution of a prednisone-PEG 6000 solid dispersion into capsule were investigated by addition of pregelatinized starch. Physical state of prednisone:PEG 6000 was analyzed by X-ray diffractometry, and scanning electron microscopy. Capsule formulations containing prednisone-PEG 6000 and pregelatinized starch showed superior dissolution properties (> 95% in 60 min) when compared with reference capsules without disintegrant (< 45% in 60 min). Water uptake and disintegration time were directly correlated with pregelatinized starch amount. The morphology of prednisone-PEG 6000 particles with disintegrant was analyzed by SEM, showing a novel surface structure. Thus, solid dispersions of a poorly water soluble drug combined with a disintegrant were confirmed as a valid approach to the improvement of drug dissolution.

Mechanical properties of short flax fibre bundle/polypropylene composites: Influence of matrix/fibre modification, fibre content, water uptake and recycling

The aim of this work was to compare the effect of modification way of short flax fibre bundle/polypropylene (PP) composites on mechanical properties. Modification was carried out on fibre surface and also modifying PP matrix using several amounts of maleic anhydride-polypropylene copolymer (MAPP) as compatibilizer. The optimum doses of two different MAPP compatibilizers have been obtained. The effect of fibre bundle loading on composite mechanical properties was also analysed. The influence of water uptake on the sorption characteristics of composites has been studied by immersion in distilled water at room temperature. The effects of fibre bundle loading and also the use of MAPP modification on both water sorption and mechanical properties were also evaluated. Results showed that using MAPP as coupling agent, mechanical properties of composites improved, and water uptake rate clearly decreased. However, after long period of water immersion mechanical properties drastically decreased. On the other hand, mechanical recycling of flax fibre bundle/PP composites has been shown to be feasible.

Environmental effects on the degradation behaviour of sisal fibre reinforced polypropylene composites

The environmental degradation behaviour on the physical and mechanical properties of short sisal/PP composites has been studied with special reference to the influence of ageing conditions like treatment with water and UV radiation. The dependence of water uptake on the sorption characteristics of sisal/PP composites was evaluated by immersion in distilled water with respect to fibre loading, temperature and chemical treatment. It is found that water uptake increases with increase of fibre loading due to the increase in cellulose content. The raise of temperature up to 70 °C is accompanied by an increase of the rate and extent of sorption. Chemical treatments such as urethane derivative of PPG, PMPPIC and MAPP were given to sisal fibre. All chemically modified fibre composites showed lower uptake than the unmodified composites. This is because all chemical treatments given to sisal fibre reduce its hydrophilicity thereby favouring strong interfacial adhesion between the fibre and PP matrix. The influence of water uptake on the tensile properties of sisal/PP composites was studied. Tensile properties decreased with water uptake, time of immersion and fibre loading. The behaviour was strongly dependent on the chemical treatment and fibre orientation. The influence of the tensile properties of sisal/PP composites exposed to UV radiation was studied. The tensile properties were found to decrease with increase in the time of exposure to UV radiation. The reduction in properties is due to chain scission and degradation occurring to PP molecules as a result of photooxidation promoted by ultraviolet radiation. As a result of UV irradiation, surface cracks can be seen on neat PP and PP composites which can be evidenced from SEM photos. The retention of tensile properties increased with increase of fibre loading.