Water Vapor Sorption Properties Research Articles

Resistance against fungal decay of Scots pine sapwood modified with phenol-formaldehyde resins with substitution of phenol by lignin pyrolysis products

Abstract Phenol-formaldehyde (PF) resins can be impregnated and cured in situ to improve the woods dimensional stability and decay resistance. In search of renewable alternatives, the substitution of phenol by lignin cleavage products (LCP) has been discussed. However, the different chemical nature may affect the performance of the resin against fungal decay, formaldehyde emission, and equilibrium moisture content. In this study, 30 % (w/w) of the phenol in PF resins were substituted by LCP obtained from microwave-assisted pyrolysis. Scots pine sapwood was modified with the resin. The decay resistance against Rhodonia placenta, Gloeophyllum trabeum, and Trametes versicolor was determined. Additionally, effects of specimen organisation within the Petri dish, different substrates, length of leaching, and type of inoculum were studied. Further, the materials water vapor sorption properties and formaldehyde emission were determined. All modifications effectively reduced fungal decay. With 10 % weight percent gain (WPG), initial decay was detected, while 20 % WPG and 30 % WPG provided efficient protection. The substitution of phenol increases the formaldehyde emission. While further reduction in formaldehyde in the resin admixture or formaldehyde scavengers may be required, the method described herein can be used to partly replace fossil-based phenol, while maintaining good fungal resistance.

Structural and Physiological Properties of Footwear Textiles

Abstract Textile uppers in the form of fitted knitted fabrics are now gaining in importance in the production of commercial footwear. The subject of this study was twelve different textile uppers and two reference leather materials. Structural properties and parameters of physiological comfort were characterized for selected variants. In order to analyze the thermo-physiological properties of the upper parts of the footwear, air permeability, thermal insulation properties, water vapor permeability and sorption properties were measured. Among the variants of textile uppers analyzed, the most desirable functional properties were shown by knitted fabrics made on cylindrical crochet machines of large diameters. The varnished cowhide leather variant was characterized by the worst hygienic properties.

A Tailored Approach in the Bentonite-like Raw Material Characterization Using Thermal and Water Sorption Techniques

Clayey raw materials present a wide variety of uses depending on their specific composition. Bentonite-like clays are considered suitable candidates to be used in some industrial applications, such as pharmaceutics, catalysis, antibacterial agents or food additives because of their highly desired adsorption properties, concretely regarding water vapor behavior. In the present study, a specific methodology for the characterization of some clayey raw materials used in the ceramic industry and its correlation with water vapor sorption properties is presented. Six different clayey raw materials have been wholly characterized until their specific chemical formula are obtained, and their water vapor adsorption behavior was correlated to their specific composition. The whole protocol has been validated with certified standard reference materials. The obtained results show a relationship between montmorillonite content in clay with water vapor adsorption behavior and certain thermal events of clayey particles, which can help the industry to understand product behavior and characterization during ceramic manufacturing process.

Assessment of the Water Sorption Capacity of Rifaximin using Dynamic Vapor Sorption Technique for Optimization of the Choice of Excipients and Manufacturing Environment of Rifaximin Tablets.

Rifaximin, a medication of the rifamycin family with two distinct strengths of 200 mg and 550 mg in tablet form, is useful for the treatment of travelers' diarrhea. It has a solid yellow hue and is very hygroscopic in nature. It exhibits a variety of polymorphic forms such as α, β, γ, δ and ε depending on bonded moisture. These polymorphs' varying chemical and physical characteristics, such as solubility and water content, may have a big impact on in vivo absorption, which in turn affects efficacy and safety. Therefore, understanding the polymorphic stability of Rifaximin is crucial for formulating Rifaximin tablets. The current effort focuses on the understanding of water vapor sorption properties to control the polymorphic stability of rifaximin in the tablet formulation using the appropriate selection of excipients and manufacturing process. The dynamic vapor sorption method in the range of 0-90% relative humidity at 25 °C is used for understanding the sorption properties of drug substances and drug excipient mixtures; the state-of-the-art techniques of the X-ray diffraction method are used to identify polymorph conversions; and dissolution procedures are used for in-vitro correlation studies. The sorption study data reveals that Rifaximin is highly unstable at relative humidity conditions above 36%. When using excipients that have a low tendency to adsorb water in the formulation, the polymorphic results don't show any change in their intended form, and the in vitro dissolution data show an equivalency with the reference drug product. The study prompted a successful outcome-oriented development of the formulation processing environment conditions design to develop a test formulation that has adequate in vitro dissolution profiles, with the reference product showing the highest similarity and stability. The overall study explained here is useful for swiftly gaining insight into the sorption characteristics of Rifaximin, and it contributed to the widespread acceptance of Rifaximin Tablets as a treatment option.

Cellulose acetate/silica composites: Physicochemical and biological characterization

Cellulose acetate is of remarkable scientific interest, becoming more useful when is used in obtaining of the composite materials containing nanoparticles, as result of its improved properties. Thus, cellulose acetate/silica composite films obtained by casting the solutions of cellulose acetate (CA)/tetraethyl orthosilicate (TEOS) in different mixing ratios were analyzed in this paper. The impact of TEOS addition, and implicitly of the silica nanoparticles on the mechanical strength, water vapor sorption properties and antimicrobial activity of the cellulose acetate/silica films were mainly monitored. The results of the tensile strength tests were discussed in correlation with data obtained from Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. It was found that samples with low TEOS content show improved mechanical strength compared to samples with high amounts of TEOS. The microstructural characteristics of the studied films affect their moisture sorption capacity so that the weight of the adsorbed water increases with the addition of TEOS. These features are complemented with the antimicrobial activity against Staphylococcus aureus and Escherichia coli bacterial species. The obtained data show that the cellulose acetate/silica films, and especially those with low silica content have improved properties that can recommend them for applications in the biomedical field.

Large Degree of Variation in Sorption Properties within a System of Isoreticular, Mixed-Ligand Ni- and Co-Based 2-Periodic Metal–Organic Frameworks

Two Ni-based and two Co-based mixed-ligand metal–organic frameworks (MOFs), which are all isoreticular with each other, are shown to have a large variation in nitrogen, carbon dioxide, hydrogen, and water vapor sorption properties, despite their similar structures. The MOFs have 1,2-bis(4-pyridyl)ethane (bpe) as the common ligand with the second ligand being either 2-nitroterephthalate (2-nta) or 2-bromoterephthalate (2-bta) for the Ni-based MOFs or 2-nta or 2-aminoterephthalate (2-ata) for the Co-based MOFs. The four MOFs have the formula [Ni(2-nta)(bpe)(H2O)2]n·2(DMA)n (1), [Ni(2-bta)(bpe)(H2O)2]n·2.8(DMF)n (2), [Co(2-nta)(bpe)(H2O)2]n·2(DMA)n (3), and [Co(2-ata)(bpe)(H2O)2]n·3(DMA)n·(H2O)n (4), respectively, where DMA = N,N′-dimethylacetamide and DMF = N,N′-dimethylformamide. Variable-temperature powder X-ray diffraction (VT-PXRD) studies indicate that the activated MOF structures are different from those of the as-synthesized MOFs, showing that the 2-periodic layers are dynamic upon desolvation. For the same metal ion, the MOF involving the 2-nta ligand has higher sorption, while sorption for the Ni-based MOFs is higher than for the Co-based MOFs. MOF 1 has the highest sorption within the isoreticular series and also has the highest sorption (the highest for water vapor) compared to other MOFs with the same or related ligands.

Anti-cluster behavior and its mechanism during water vapor sorption in chitin and chitosan membranes

Alternating petroleum-based plastics to inexhaustible natural resource-based ones is an important issue worldwide, especially for the plastic packaging application. Polysaccharides are soluble in liquid water or swelled with liquid water; thus, they have been considered unsuitable materials for this application. Hence, reports on water vapor (i.e., gas) sorption properties of polysaccharide membranes are few. Polymers are well-known to demonstrate water vapor clustering during water vapor sorption. Unlike others, anti-cluster behavior for water vapor was discovered for chitin and chitosan membranes in this study. Therefore, chitin and chitosan membranes possess resistance to moisture during storage of a package, particularly for dried food. The anti-cluster mechanism was also revealed in this study. The sorption of water vapor in both membranes was considered a 1:1 interaction between hydrophilic groups and water molecules and the manner by which water molecules act on hydrophilic groups has an order.

Static Water Vapor Sorption Properties of Honey

Abstract Static sorption properties of pine honey (PH) and citrus honey (CH) were studied at 20, 30 and 40°C. Yeast formation was observed on the surface of honeys at water activity (aw)>0.7 at all temperatures. Visible yeast formation (YF) took place earlier in PH than in CH under the same conditions due to its characteristic higher pH and lower monosacchride content. The temperature was insignificantly effective on YF (p>0.05). The honeys exhibited a sorption isotherm (SI) in the shape of a “J”. Their SIs exhibited desorption and adsorption at aw<0.7 and aw>0.7, respectively and the desorption part was almost linear. Aw=0.7 emerged as a border between the absence and presence of YF and between the desorption and adsorption. The SIs of honeys were insignificantly affected by temperature (p>0.05). PH had a significantly lower SI than that of CH (p≤0.05) due to its characteristic lower monosacchride content. GAB equation exhibited a good fit to the honeys' SIs. Sorption heat vs equilibrium moisture content (EMC) revealed monolayer, multilayer and loosely bound free water regions in the SIs of PH and CH.

Water vapor sorption properties on coals affected by hydrophilic inorganic minerals and pore fissures

It is essential to understand the law by which coal adsorbs water to prevent coal and rock disasters in the mining process. However, the hydration of coal containing inorganic minerals is seldom studied. In this study, X-ray diffraction (XRD), low-pressure nitrogen adsorption (LPNA), and low-temperature carbon dioxide adsorption (TCA) experiments were performed on coal samples to obtain inorganic mineral compositions and pore structure characteristics. Then, vacuum vapor sorption analyzer (VVS) experiments were carried out on coal samples. GAB and Freundlich models were used to classify the strong adsorption region, weak adsorption region, and critical humidity for monolayer adsorption. The relationship between the amount of adsorbed water and the coal's pore structure and surface chemical properties was discussed. Then, the reason for the difference in specific surface area between N2 and H2O adsorbents was elucidated. Finally, we discuss the significance of coal-water adsorption by pyrite and clay minerals in preventing coal and dynamic rock disasters.

Helical structures and water vapor sorption properties of carrageenan membranes derived from red algae

Packaging manufactured from petroleum is stable, and its waste threatens marine life. This study proposes the use of harmless edible materials manufactured from marine plants. Carrageenan is among the natural polysaccharides derived from red algae. Water vapor sorption was studied for membrane specimens of κ-carrageenan, ι-carrageenan, and λ-carrageenan at 25 °C. κ-Carrageenan and ι-carrageenan showed double-helical structure, whereas λ-carrageenan exhibited a single-helical structure. In the solubility test of liquid water, κ-carrageenan and ι-carrageenan were swollen, and λ-carrageenan dissolved in water at 23 °C. However, these higher-order structures were maintained after the exposure of water vapor to a relative pressure of 0.9. The water vapor sorption properties in carrageenan membranes were related to the relative pressure and categorized into three relative pressure ranges, namely, from 0.0 to 0.3, from 0.3 to 0.6, and from 0.6 to 0.9. The amounts of water molecules sorbed in the membrane were correlated with the number of polar groups in each carrageenan from 0.0 to 0.3. From 0.3, the cluster of water molecules started to appear with the maintenance of the helical structures. This novel finding can potentially lead to the design of environmentally friendly packaging by using carrageenan.

Study of the water sorption and barrier performances of potato starch nano-biocomposites based on halloysite nanotubes

The barrier performances, in terms of water vapor sorption properties, gas and water barrier performances were analyzed on different starch-based nano-biocomposites. These multiphase systems were elaborated by melt blending starch and halloysite nanotubes at different contents with different plasticizers (glycerol, sorbitol and a mix of both polyols). The influence of the composition was investigated onto the structure, morphology, water sorption and barrier performances. As recently reported, halloysite nanoclay is a promising clay to enhance the properties of plasticized starch matrix. The barrier performances of nanofilled starch-based films were examined through gas and water permeabilities, diffusivity and water affinity. Glycerol-plasticized starch films give fine and more homogeneous nanofiller dispersion with good interfacial interactions, compared to sorbitol ones (alone or mixed), due to stronger and more stable hydrogen bonds. Tortuosity effects linked to the halloysite nanotubes were evidenced by gas transfer analysis, and exacerbated by the good interactions at interfaces and the resulting good filler dispersion. The influence of morphology and interfacial interactions towards water affinity was highlighted by moisture barrier properties. This was a key factor on the reduction of water diffusion and uptake with nanoclay content. A preferential water transfer was observed as a function of a plasticizer type in relation with the phenomenon of water plasticization in the nanocomposite systems.

Solvent- and Temperature-Driven Photoluminescence Modulation in Porous Hofmann-Type SrII-ReV Metal-Organic Frameworks.

A unique family of three-dimensional (3D) luminescent SrII-ReV metal-organic frameworks (MOFs), {[SrII(MeOH)5][ReV(CN)4(N)(bpen)0.5]·MeOH}n [1·MeOH; N3- = nitrido ligand, bpen = 1,2-bis(4-pyridyl)ethane, and MeOH = methanol], {[SrII(MeOH)4][ReV(CN)4(N)(bpee)0.5]·2MeOH}n [2·MeOH; bpee = 1,2-bis(4-pyridyl)ethylene], and {[SrII(bpy)0.5(MeOH)2][ReV(CN)4(N)(bpy)0.5]}n (3·MeOH; bpy = 4,4'-bipyridine), is reported. They are obtained by the molecular self-assembly of Sr2+ ions with tetracyanidonitridorhenate(V) metalloligands, [ReV(CN)4(N)]2-, and pyridine-based organic spacers (L = bpen, bpee, bpy). Such a combination of molecular precursors results in bimetallic SrII-ReV cyanido-bridged layers further bonded by organic ligands into pillared Hofmann-type coordination skeletons. Because of the formation of {ReV-(L)-ReV} moieties providing emissive metal-to-ligand charge-transfer states, 1·MeOH-3·MeOH exhibit solid-state room-temperature photoluminescence tunable from green to orange by the applied organic ligand. The most stable MOF of 3·MeOH, based on the alternating {ReV-(bpy)-ReV} and {SrII-(bpy)-SrII} linkages, exhibits three interconvertible, variously solvated phases, methanol-solvated 3·MeOH, hydrated {[SrII(bpy)0.5(H2O)2][ReV(CN)4(N)(bpy)0.5]·0.6H2O}n (3·H2O), and desolvated {[SrII(bpy)0.5][ReV(CN)4(N)(bpy)0.5]}n (3). Their formation was correlated with water and methanol vapor sorption properties investigated for 3·H2O. The solvent content affects the luminescence mainly by tuning the emission energy within the series of 3·MeOH, 3·H2O, and 3. All of the obtained compounds exhibit temperature-driven modulation of luminescence, including the shift of the emission maximum and lifetime. The thermochromic luminescent response was found to be sensitive to the presence and type of solvent in the crystal lattice. This work shows that the construction of [ReV(CN)4(N)]2--based MOFs is an efficient route toward advanced solid luminophores tunable by external stimuli such as solvent or temperature.

Water Vapor Sorption and Diffusivity in Bio-Based Poly(Ethylene Vanillate)-PEV.

The dynamic and equilibrium water vapor sorption properties of amorphous and highly crystalline poly(ethylene vanillate) (PEV) films were determined via gravimetric analysis, at 20 °C, over a wide range of relative humidity (0–95% RH). At low RH%, the dynamic of the sorption process obeys Fick’s law while at higher relative humidity it is characterized by a drift ascribable to non-Fickian relaxations. The non-Fickian relaxations, which are responsible for the incorporation of additional water, are correlated with the upturn of the sorption isotherms and simultaneously the hysteresis recorded between sorption and desorption cycles. The sorption isotherms of amorphous and highly crystalline PEV are arranged in the same concentration range of that of PET proving the similarity of the two polyesters. Water diffusion coefficients, whose determination from individual kinetic sorption/desorption curves required treatment with the Barens–Hopfenberg model, were demonstrated to be ≈10× higher for amorphous PEV compared to amorphous PET. Such a difference originates from the enhanced segmental flexibility of PEV chains.

Water Vapor Sorption Properties on Coals Affected by Hydrophilic Inorganic Minerals and Pore Fissures

Water Vapor Sorption Properties on Coals Affected by Hydrophilic Inorganic Minerals and Pore Fissures

Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams

Summary Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.

Effects of counter cations on the water vapor sorption properties of alginic acid and alginates

AbstractIn this study, the water vapor sorption of four types of alginate, namely, alginic acid (Alg), Na‐Alg, Ca‐Alg, and NH4‐Alg, were measured, and the effect of differences in counter cations on water vapor solubility and crystallization mechanism associated with the arrangement of hydrogen bonds generated during humidification was investigated. The sorption amounts in the high‐humidity region can be arranged as follows: Na‐Alg > NH4‐Alg > Ca‐Alg > Alg. All samples formed a (C)‐type double helix structure before and after the sorption based on the results of Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction. The counter cation affects the arrangement of the hydrogen bonds in this structure. Only Ca‐Alg possessed a pseudocrosslinking among the (C)‐type double helix structures due to the divalent Ca2+ ions, which induced variations in the crystal arrangement behavior of the other three samples before and after sorption. Cases I–III show a case of how the orientation is aligned with a new hydrogen bond and classified for each sample.

Gas dehydration using the ionic liquid [EMIM][MeSO3] supported on silica gel – Structural and water vapor sorption properties

Structural and water vapor sorption properties of supported ionic liquid phase (SILP) materials, here of the ionic liquid [EMIM][MeSO3] coated on silica gels, were studied. The distribution of the IL over the silica supports is uniform. The porosity of the SILPs shows good agreement with expected values based on the density of the pure IL. The water sorption in pure [EMIM][MeSO3] as well as by the SILPs can be described by Guggenheim-Anderson-de Boer sorption isotherms. If the silica surface is covered by at least a complete monolayer of IL, the surface has no noticeable effect on the sorption capacity, and the capacity of the SILP corresponds to that of the pure IL until capillary condensation occurs. SILPs are promising candidates for gas dehydration, as the water sorption capacity per mass of silica is about six times higher compared to uncoated silica.

Water Vapor Sorption Properties of Illinois Shales Under Dynamic Water Vapor Conditions: Experimentation and Modeling

AbstractWater vapor adsorption/desorption isotherms are measured on five shales from Illinois basin by dynamic vapor sorption method. The experimental adsorption data are modeled by the Guggenheim, Anderson, and De Boer model and the Freundlich model over the entire range of measured relative humidity (Rh) values (0–0.95). Modeling results show that shale hydration is controlled by surface chemistry at low Rh through a strong intermolecular bonding, while is mainly influenced by the pore structure at high Rh (>0.9) through capillary condensation. This is consistent with the progressive decrease of isosteric heat of adsorption with water content, obtained by the Clausius‐Clapeyron equation. Exceptionally, for the one shale containing 8.6% montmorillonite, mesopore condensation only accounts for 33% of the measured water adsorption even at Rh ~0.95 due to the limited external pores and the important role of clay swelling. The specific surface area defined by Guggenheim, Anderson, and De Boer analysis as available for water adsorption is larger than that available for low‐pressure N2 adsorption due to the complex surface chemistry. The one shale rich in expansive montmorillonite and with a large interlayer capacity for water but inaccessible to N2 molecules conditions this result. Among the other four shales, one with high kerogen content behaves the highest water adsorption, possibly due to the high content of oxygen‐containing functional groups and the potentially high pore volume of kerogen. These findings contribute to a better understanding of water storage and transport behavior in shales and impact behavior relevant to structures and reservoirs founded in such media.

Water vapour sorption properties of thermally modified and pressurised hot-water-extracted wood powder

AbstractThe objective of the study was to investigate the water vapour sorption behaviour of thermally modified (TM) wood powder, e.g. ground wood prepared from waste streams of TM solid wood, and wood powder that was extracted in pressurised hot water. Solid spruce wood was TM in steam conditions (210°C for 3 h), milled and hot-water-extracted (HWE) at elevated pressure (140°C for 1 h). The results evidence that the hot-water extraction reduced the water sorption and the accessible hydroxyl group concentration by the removal of amorphous carbohydrates. In contrast, the enhanced cross-linking of the cell wall matrix and the annealing of amorphous matrix polymers during thermal modification reduced the sorption behaviour of wood additionally, without further reducing the hydroxyl accessibility. These additional effects of thermal modification were at least partially cancelled by hot-water extraction. The results bring novel insights into the mechanisms that reduce the water vapour sorption of wood by compositional and structural changes induced by heating.

Effect of Heat Treatment on Water Vapor Adsorption by Opal Structures and Their Effective Refractive Index

We have studied water vapor sorption properties of close-packed opal structures made up of monodisperse spherical silica particles 150 to 350 nm in diameter. The results attest to polymolecular water adsorption followed by capillary condensation in meso- and micropores within the structure-forming particles. The maximum adsorption value, ~0.13 g of H2O per gram of dry SiO2, essentially coincides with the specific volume of inner pores in the particles. The annealing temperature has been shown to influence the adsorption properties and effective refractive index of the opal photonic crystals. The refractive index of dry and adsorbed water-filled opal structures has been determined as a function of annealing temperature.