Hygroscopic Behavior Research Articles

Structural behaviour of unstabilized rammed earth constructions submitted to hygroscopic conditions

Rammed earth constructions exhibit strength and deformation properties that evolve as a function of the relative humidity of the air in contact with the walls. This effect must be considered in the structural design of the construction. This work studies, through finite element simulation, the impact of the hygroscopic transfers through the wall on the structural response of a classical two-storey rammed earth building. The coupling between the mechanical and the hygroscopic behaviour is considered by the concept of effective stress for unsaturated soils, in order to reproduce the effect of suction on the strength, the stiffness and the volumetric variations of the rammed earth. The simulations show classical deformation of the structure due to distributed load on the floors while the hygroscopic changes in the rammed earth (essentially drying) induce additional displacements of the walls that remain in a very acceptable range. Finally, an extreme case is envisaged in which the loads on the floors are increased excessively in order to study the plastic response of the wall.

Adsorption isotherms of the red mombin powder produced in spouted bed dryer

ABSTRACT Red mombin is a seasonal fruit and susceptible to degradation reactions due to its high water content. This highlights the need to use processes that prolong its life and make it available all year round, including to markets away from the production sites. Thus, the objective of this study was to produce red mombin pulp powder in spouted bed dryer, evaluate it regarding physical and chemical parameters and assess its hygroscopic behavior at temperatures of 20, 30 and 40 °C, fitting the models of the GAB, Oswin and Peleg to the experimental data. The results of the physical and chemical analyses showed intermediate wetting time of 0.39 g min-1, solubility higher than 60% and mean flowability with Hausner ratio and Carr index of 1.26-1.34 and 0.21-0.25, respectively. The powder particles exhibited spherical shape, smooth surface and some irregularities, with tendency to form agglomerates. The isotherms had a type-II sigmoidal behavior, and the Peleg model, at all temperatures, showed the best fits to the experimental data with determination coefficients above 0.99 and mean percentage deviations lower than 2.0%.

Powdered tucupi condiment: sensory and hygroscopic evaluation

Abstract Tucupi is a fermented liquid obtained from cassava (Manihot esculenta Crantz), very much appreciated by the traditional cuisine of Northern Brazil. However, there are no scientific reports on its use in the formulation of products. Thus, the present study aimed to elaborate a powdered condiment with tucupi, as well as to assess the product’s sensory acceptability and its hygroscopic behavior. The powdered tucupi used in the formulation of the condiment was obtained by drying in a spray dryer. The product underwent sensory evaluation for its acceptability regarding the attributes of color, aroma, flavor, and overall impression and a purchase intention test was applied by hedonic scale. The acceptability index was 80% for overall impression and the purchase intention test indicated that 94% of the judges would be willing to buy the product. The product’s moisture sorption isotherms presented type-II behavior for adsorption and type-III for desorption, at 25 °C. The hygroscopic behavior indicated that the product is more susceptible to spoilage changes when stored in an environment with relative humidity above 60% and the Peleg model showed an excellent performance on predicting the product’s moisture sorption isotherms.

Individual Test Rig for Measuring the Creep Behaviour of Corrugated Board for Packaging

Corrugated board is one of the most important and most popular packaging materials worldwide for transporting goods. Due to its hygroscopic behavior, it has a tendency to creep when subjected to stress under a constant load, which can ultimately result in loss of strength, with possible damage to products. The creep behavior of corrugated board is still a largely under-researched area. This paper attempts to examine the long-term behavior of corrugated board during use more precisely than before, and presents the first step and results of the research process. For the measurement, a compact and high-precision individual test rig was developed and used, in order to reduce the side effect of coupled systems, that is, to avoid their mutual influence. This paper successfully presents results reproducible with the described test rig apparatus for determining the creep behavior of corrugated board. It will be continued to publish further results of the research in the near future.

Hygroscopic equilibrium of microencapsulated extract of passion fruit seed and its effect on the antioxidant capacity

AbstractThe hygroscopic behavior of microcapsules of antioxidant extract of defatted passion fruit seed, produced using spray drying technique, was analyzed at 20 and 40 °C by the static method with saturated saline solutions. The isosteric heat of sorption of the microcapsules, concentration of phenolic compounds and piceatannol, and the antioxidant capacity using ABTS and DPPH methods were measured during storage at different relative humidities. The isotherms were classified as GAB isotherms, exhibiting a Type II behavior. Isosteric heat of sorption decreased when the relative humidity increased and critical equilibrium moisture reached 61%. The microencapsulated extracts retained their antioxidant capacities within the evaluated conditions, what suggests that it may be applied in food at any of these water activity values.Practical applicationsPiceatannol is a stilbene with expressive antioxidant capacity which can be found in passion fruit seeds. In this work, the seeds were used to obtain the crude hydroethanolic extract which was microencapsulated by spray drying. The hygroscopic behavior of the microencapsulated extract of piceatannol was evaluated by fitting the data on different isotherm theoretical models. It was possible to verify the interference of the water activity in the antioxidant capacity and establish a relationship with possible critical storage conditions of the microencapsulated extract.

Water transport kinetics and thickness swelling behavior of natural fiber-reinforced HDPE/CNT nanocomposites

Abstract This study mainly focused on investigating the effect of carbon nanotubes (CNTs) on the long-term hygroscopic behavior of composites based on old corrugated container (OCC) and high density polyethylene (HDPE). Composite profiles were made by melt compounding and then injection molding. For CNT as a reinforcing agent, different loading levels of 0, 1, 3 and 5 phc was used. The amount of HDPE and coupling agent was fixed at 50 wt% and 2 phc for all formulations, respectively. The governing kinetic behavior of water transport in the studied composites was examined by immersing them in water at room temperature for several weeks, and water diffusion coefficients were also calculated by evaluating the water absorption isotherms. In addition, a predictive model for determining the thickness swelling rate of the samples was developed by Shi and Gardner model. Results indicated that the composites filled with CNT had considerably lower water absorption compared with those samples without ones. The absorption processes for all families of composites were found to exhibit Fickian diffusion behavior. It was found that that equilibrium thickness swelling and also shorter equilibrium time (the time to reach the equilibrium thickness swelling) decreased with increase of CNT loading. Furthermore, the swelling model provided a good predictor of the hygroscopic thickness swelling process of HDPE/OCC/CNT hybrid composites. Also, a good linear relationship was fit between swelling rate parameter ( K SR ) and CNT contents. The minimum K SR values were observed in composites made of 5 phc CNT.

Harnessing the hygroscopic and biofluorescent behaviors of genetically tractable microbial cells to design biohybrid wearables.

Cells' biomechanical responses to external stimuli have been intensively studied but rarely implemented into devices that interact with the human body. We demonstrate that the hygroscopic and biofluorescent behaviors of living cells can be engineered to design biohybrid wearables, which give multifunctional responsiveness to human sweat. By depositing genetically tractable microbes on a humidity-inert material to form a heterogeneous multilayered structure, we obtained biohybrid films that can reversibly change shape and biofluorescence intensity within a few seconds in response to environmental humidity gradients. Experimental characterization and mechanical modeling of the film were performed to guide the design of a wearable running suit and a fluorescent shoe prototype with bio-flaps that dynamically modulates ventilation in synergy with the body's need for cooling.

Potential of the hornification treatment on eucalyptus and pine fibers for fiber-cement applications

In the industry of cement-based products, various lignocellulosic materials are used as reinforcing elements. These cellulosic materials are presented as potential alternatives because of their sustainability, low cost and technical features. However, plant fibers, in spite of good mechanical performance as reinforcement materials, exhibit a number of shortcomings in relation to durability in the alkaline environment of cementitious materials as well as dimensional variation due to their characteristic hygroscopic behavior. Thus, hornification emerges as an alternative, economic and simple pretreatment that is expected to minimize these problems. This study evaluated the physical, chemical and morphological effects of four hornification cycles on pine pulp and innovative eucalyptus pulps, both bleached and unbleached, proving that the treatment does not deteriorate the characteristics of interest of the fibers. Hornification modifies fiber surfaces and reduces their water absorption capacity, turning the pulps into more suitable materials and giving them the technical capability to reinforce brittle inorganic matrices.

Hygroscopic properties of potassium chloride and its internal mixtures with organic compounds relevant to biomass burning aerosol particles

While water uptake of aerosols exerts considerable impacts on climate, the effects of aerosol composition and potential interactions between species on hygroscopicity of atmospheric particles have not been fully characterized. The water uptake behaviors of potassium chloride and its internal mixtures with water soluble organic compounds (WSOCs) related to biomass burning aerosols including oxalic acid, levoglucosan and humic acid at different mass ratios were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA). Deliquescence points of KCl/organic mixtures were observed to occur at lower RH values and over a broader RH range eventually disappearing at high organic mass fractions. This leads to substantial under-prediction of water uptake at intermediate RH. Large discrepancies for water content between model predictions and measurements were observed for KCl aerosols with 75 wt% oxalic acid content, which is likely due to the formation of less hygroscopic potassium oxalate from interactions between KCl and oxalic acid without taken into account in the model methods. Our results also indicate strong influence of levoglucosan on hygroscopic behaviors of multicomponent mixed particles. These findings are important in further understanding the role of interactions between WSOCs and inorganic salt on hygroscopic behaviors and environmental effects of atmospheric particles.

Cocrystallization as a tool to solve deliquescence issues: The case of l-lactic acid

l-Lactic acid is an organic acid used in various fields such as food, cosmetic or pharmaceutical industry. It furthermore is the building-block of poly-lactic acid, a biodegradable and bioavailable polymer. Still, handling l-lactic acid under its solid form remains less straightforward mainly due to its deliquescent behavior, a phase transition from the solid to the dissolved state resulting from air humidity absorption. If several techniques are already known to avoid or reduce deliquescence, the use of cocrystallization in this context is still poorly investigated. In this paper, we investigate whether cocrystallization can be used as a suitable solution for deliquescence in the case of l-lactic acid.Out of 32 possible coformers tested, four were found to form cocrystals with l-lactic acid and the crystal structures of 1:1 l-lactic acid:d-tryptophan and 1:1 l-lactic acid:3-nitrobenzamide were determined. The hygroscopic behavior of these latter two was studied and compared to the behavior of pure l-lactic acid. Significant improvement was observed: dynamic vapor sorption at 25°C revealed that water absorbed at 90% relative humidity dropped from 1.3157g/gsample to 0.0017g/gsample or 0.0299g/gsample, with cocrystals of d-tryptophan and 3-nitrobenzamide respectively. This illustrates the effectiveness of cocrystallization as a tool to treat deliquescent materials.

Impact of hydrogenated starch hydrolysate on glass transition, hygroscopic behavior and crystallization of isomalt-based systems

Impact of hydrogenated starch hydrolysate on glass transition, hygroscopic behavior and crystallization of isomalt-based systems

Biological invasion in the indoor environment: the spread of Eurotium halophilicum on library materials

Volumes from an archive of the University of Milan showed whitish-grey discolouration putatively caused by microorganisms. Microscopic and viability assays proved that discolouration from two volumes were characterized by a marked presence of viable fungi, demonstrating that they were mainly biological in nature. Fungal sequences were phylogenetically most closely related to Eurotium, Aspergillus, Candida, Penicillium, Alternaria, Phaeosphaeria, Capnodiales and Pleosporales taxa. SEM analysis showed that Eurotium halophilicum is dominant on the two infected volumes. Viable airborne fungal loads near the two volumes were higher than recommended maximum values, demonstrating that airborne fungi could represent a source of risk. The airborne microbial community sampled in two different seasons was composed by fungi belonging in the genera Aspergillus, Candida and Eurotium. The detection of E. halophilicum also in the archival air indicated a possible source of contamination. Fluctuations of thermo-hygrometric values were also observed in the archive in the different seasons. The occurrence of white efflorescence on the stored volumes most likely depended on the lack of both a dusting programme and air-conditioning, and insufficient ventilation in the repository, and, on the hygroscopic behaviour of the binding materials used in the manufacture of the volumes.

Effect of differential surface anisotropy on performance of two plate shaped crystals of aspirin form I

Differential surface anisotropy of different crystals of the same API can have a significant impact on their pharmaceutical performance. The present work investigated the impact of differential surface anisotropy of two plate-shaped crystals of aspirin (form I) on their hygroscopicity, stability and compaction behavior. These crystals differed in their predominant facets (100) and (001) and were coded as AE-100 & E-001. (100) facets exposed polar carbonyl groups which provided hydrophilicity to the facets. In contrast, (001) facets possessed hydrophobicity as they exposed non-polar aryl and methyl groups. Both the samples showed different degradation behavior, at various stability conditions (i.e. 40°C/75%RH, 30°C/90%RH and 30°C/60%RH) and different time intervals. Polar groups of aspirin have been reported to be prone to hydrolysis due to which AE-100 was less stable than E-001. Dynamic vapor sorption (DVS) analysis at different simulated stability conditions also supported this observation, wherein AE-100 showed higher moisture sorption than E-001. Both the samples having similar particle size, shape, surface area and hardness value, showed differences in their compactibility. However, milling narrowed down the predominance of facets and both the milled samples showed similar stability and compaction behavior. This study was also supported by surface free energy determination, molecular modeling and face indexation of unmilled and milled samples.

Real-Time Investigation of Chemical Compositions and Hygroscopic Properties of Aerosols Generated from NaCl and Malonic Acid Mixture Solutions Using in Situ Raman Microspectrometry.

Recently, ambient sea spray aerosols (SSAs) have been reported to undergo reactions with dicarboxylic acids (DCAs). Several studies have examined the hygroscopic behavior and chemical reactivity of aerosols generated from NaCl-DCA mixture solutions, but the results have varied, especially for the NaCl-malonic acid (NaCl-MA) mixture system. In this work, in situ Raman microspectrometry (RMS) was used to simultaneously monitor the change in chemical composition, size, and phase as a function of the relative humidity, for individual aerosols generated from NaCl-MA solutions, during two hygroscopic measurement cycles, which were performed first through the dehydration process, followed by a humidification process, in each cycle. In situ RMS analysis for the aerosols showed that the chemical reaction between NaCl and MA occurred rapidly in the time scale of 1 h and considerably in the aqueous phase, mostly during the first dehydration process, and the chemical reaction occurs more rapidly when MA is more enriched in the aerosols. For example, the reaction between NaCl and MA for aerosols generated from solutions of NaCl:MA = 2:1 and 1:2 occurred by 81% and 100% at RH = 42% and 45%, respectively, during the first dehydration process. The aerosols generated from the solution of NaCl:MA = 2:1 revealed single efflorescence and deliquescence transitions repeatedly during two hygroscopic cycles. The aerosols from NaCl:MA = 1:1 and 1:2 solutions showed just an efflorescence transition during the first dehydration process and no efflorescence and deliquescence transition during the hygroscopic cycles, respectively. The observed different hygroscopic behavior was due to the different contents of NaCl, MA, and monosodium malonate in the aerosols, which were monitored real-time by in situ RMS.

Hygroscopic behavior of water-soluble matter in marine aerosols over the East China Sea

In this study, we investigated hygroscopic properties of water-soluble matter (WSM) in marine aerosols over the East China Sea, which were collected during a Natural Science Foundation of China (NSFC) sharing cruise in 2014. Hygroscopic growth factors (g) of WSM were measured by a hygroscopicity tandem differential mobility analyzer (H-TDMA) with an initial dry particle mobility diameter of 100nm. The observed g at 90% relative humidity (RH), g(90%)WSM, defined as the ratio of the particle diameter at 90% RH to that at RH<5% (initial dry diameter), ranged from 1.67 to 2.41 (mean±std: 1.99±0.23). The g values were lower than that of seawater (2.1) but comparable with those reported for marine aerosols (1.79–2.08). The H-TDMA retrieved hygroscopicity parameter of WSM, κWSM, ranged from 0.46 to 1.56 (0.88±0.35). The observed g(90%)WSM during the daytime ranged from 1.67 to 2.40 (1.95±0.21) versus 1.71 to 2.41 (2.03±0.26) during the nighttime. κWSM was 0.81±0.32 in the daytime and 0.95±0.40 in the nighttime. The day/night differences of g(90%)WSM and κWSM indicated that nighttime marine aerosols were more hygroscopic than those in daytime, which was likely related to enhanced heterogeneous reaction of ammonium nitrate in nighttime and the higher Cl−/Na+ molar ratios obtained (0.80) in nighttime than those (0.47) in daytime. Inorganic ions accounted for 72–99% of WSM with SO42− being the dominant species, contributing to 47% of the total inorganic ion mass. The declined g(90%) comparing with sea water was likely due to the transport of anthropogenic aerosols, chemical aging of dust particles, the contribution of biomass burning products, and the aerosol hygroscopic growth inhibition of organics.

Understanding the drying kinetic and hygroscopic behaviour of larvae of yellow mealworm (Tenebrio molitor) and the effects on their quality

The use of insects for preparing high nutritional value foods is emerging. The dehydration kinetic of yellow mealworms larvae and its hygroscopic behaviour were described also analysing the changes in quality attributes. Blanching was performed before air drying at 50, 60 and 70 °C while sorption isotherms were studied after air drying and freeze-drying. The Page model described the dehydration kinetic at 50, 60 and 70 °C with a coefficient of determination of 0.993. Moisture diffusion coefficients between 4.85×10-11 and 1.62×10-10 m2/s were estimated and their temperature dependence was described by the Arrhenius equation, estimating an Ea of 52.1 kJ/mol. The Guggenheim-Anderson-de Boer model well fitted experimental data, showing isotherms of type II and estimating a monolayer value of 0.05 g H2O/g dry matter. Blanching significantly modified the adsorption isotherms, increased the moisture of fresh larvae without affecting their proximate composition. Rehydration after lyophilisation produced higher colour degradation probably due to the increase of enzymatic activity.

Phase state of ambient aerosol linked with water uptake and chemical aging in the southeastern US

Abstract. During the summer 2013 Southern Aerosol and Oxidant Study (SOAS) field campaign in a rural site in the southeastern United States, the effect of hygroscopicity and composition on the phase state of atmospheric aerosol particles dominated by the organic fraction was studied. The analysis is based on hygroscopicity measurements by a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA), physical phase state investigations by an Aerosol Bounce Instrument (ABI) and composition measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). To study the effect of atmospheric aging on these properties, an OH-radical oxidation flow reactor (OFR) was used to simulate longer atmospheric aging times of up to 3 weeks. Hygroscopicity and bounce behavior of the particles had a clear relationship showing higher bounce at elevated relative humidity (RH) values for less hygroscopic particles, which agrees well with earlier laboratory studies. Additional OH oxidation of the aerosol particles in the OFR increased the O : C and the hygroscopicity resulting in liquefying of the particles at lower RH values. At the highest OH exposures, the inorganic fraction starts to dominate the bounce process due to production of inorganics and concurrent loss of organics in the OFR. Our results indicate that at typical ambient RH and temperature, organic-dominated particles stay mostly liquid in the atmospheric conditions in the southeastern US, but they often turn semisolid when dried below ∼ 50 % RH in the sampling inlets. While the liquid phase state suggests solution behavior and equilibrium partitioning for the SOA particles in ambient air, the possible phase change in the drying process highlights the importance of thoroughly considered sampling techniques of SOA particles.

Relative humidity non-uniformities in Hygroscopic Tandem Differential Mobility Analyzer measurements

Hygroscopic Tandem Differential Mobility Analyzers (HTDMAs) are widely used to measure the water uptake characteristics of aerosol particles. As has been shown experimentally in the past, potential differences in the relative humidity (RH) between the aerosol and the sheath flow of the second Differential Mobility Analyzer (DMA) can lead to erroneous estimates of the apparent hygroscopic behavior of the sampled particles. A prompt phase transition, for example, may become smeared and be erroneously interpreted as non-prompt. Using a particle-tracking model, here we simulate the trajectories and the state of the particles classified in a DMA with non-uniform RH and temperature profiles. Our simulations corroborate earlier observations proving that such an experimental artifact can induce particle growth within the second DMA. Given the importance of maintaining uniform RH and temperature inside the second DMA of HTDMA systems and the limitations of existing RH and temperature sensors, we further provide suggestions for their operation.

An overview of oil palm biomass torrefaction: Effects of temperature and residence time

Biomass is characterized as high moisture content, low bulk and energy density, possesses hygroscopic behaviour and poor grindability material as compared to the superior coal. A thermal treatment called torrefaction is a heating of biomass in a temperature range between 200°C to 300°C under inert atmosphere in order to upgrade biomass properties. Torrefied biomass has many similar characteristics to coal such as low moisture content, high bulk and energy density, hydrophobic and good grindability. This paper reviews the effects of oil palm biomass torrefaction in terms of temperature and residence time. This is because comprehensive studies on torrefaction parameters need to be carried out since different parameters might affect the chemical and physical characteristic of the torrefied product. Hence, this paper aims to discuss the effects of different torrefaction temperature and residence time towards physicochemical characteristic, mass and energy yield as well as calorific value of torrefied oil palm biomass.

Physical and mechanical properties of PLA composites reinforced by TiO2 grafted flax fibers

In this study, modified TiO2 grafted flax fibers were used to reinforce PLA composites. The fibers were oxidized in order to improve the interfacial adhesion of the fibers to TiO2 film. The TiO2 film was created on the flax fiber by a Sol-Gel dip-coating technique. The interfacial adhesion of the fibers to the matrix was investigated qualitatively by microscopy, and quantitatively by measuring inter-laminar shear strength. Impact and tensile tests characterized the mechanical properties of the modified TiO2 grafted flax fiber reinforced composites. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Dynamic mechanical analysis (DMA) were used to reveal the thermal and thermo-mechanical behavior of the composites. The hygroscopic behaviors of the composites were determined by the water uptake assessment. The results showed statistically significant increase in adhesion bonding of the modified fibers to the matrix. The modified TiO2 grafted flax fibers increased the impact resistance of pure PLA by three times. The microscopic observations verified the modifications in the mechanical and physical properties of the composites. Moreover, the amount of water sorption decreased by 18% in the modified TiO2 grafted fiber reinforced composite.