Humidity Absorption Research Articles

A binary salt composite adsorbent material for solar-driven sorption-based atmospheric water harvesting

Solar-driven sorption-based atmospheric water harvesting (SSAWH) technology stands as a promising avenue for sourcing freshwater in arid and remote regions. For real-world large-scale applications, the effective water absorption capacity, broad humidity absorption range, and rapid desorption properties of adsorbent materials have been the main goals of the research area. In this context, we have developed a binary salt composite adsorbent material (PAMg-Li) for solar-driven water harvesting by integrating binary hygroscopic salts MgSO4 particles and LiCl particles, activated carbon fiber (ACF), and polyvinyl alcohol (PVA). The inherent porous structure and interconnected channels at micro and nano scales of PAMg-Li facilitate water absorption, and obtained satisfactory water absorption rate even at 30% relative humidity (RH). It has been shown to be able to achieve a high water storage capacity and realize water desorption under natural light. A home-made device based on PAMg-Li obtained a water evaporation rate of 0.084 kg/(m2·h) under solar radiation intensities ranging from 200 to 850 W/m2. The PAMg-Li material developed in this work can be a candidate for a more practical and effective choice for SSAWH.

Biodegradable materials with FDM technology under the aging effect of solar and saltwater exposure

The durability and degradation of polymers is very important for product design in terms of material choice. The degradation behavior of two biodegradable thermoplastic materials manufactured by 3D printing, Enviro ABS and PLA, was studied. The action of the sun and seawater was simulated to find out how they affect the properties of these materials over a period of 8 weeks. The yield strength, maximum elongation, ultimate tensile strength, and microscopy were analyzed, as well as dimensions and mass changes. These biodegradable materials were studied to conclude whether there is an environmentally friendly alternative to traditional ABS, being one of the most widely used petroleum-based plastics in industry and in fused deposition modeling (FDM) or fused filament fabrication (FFF). PLA showed a weight loss and increase in ultimate tensile stress on degradation by sunlight and a prolonged decrease in ultimate tensile stress on degradation by seawater due to humidity absorption. In contrast, Enviro ABS does not show a noticeable difference between the beginning and the end of the test, which leads to the conclusion that Enviro ABS is a good alternative to conventional ABS without forgetting the environmental effects that are currently involved in the manufacture, recycling and composting of this type of material.

Mechanical and Structural Behavior of Concrete Blocks with Granulated Polystyrene (PS) and Recycled Polypropylene (PP) Fibres and Their Use in Low and Medium Height Frames

ABSTRACT This research proposes to include different percentages of recycled polypropylene (PP) fibers and polystyrene (PS) granules in the manufacture of concrete blocks. They are thermoplastic materials widely used in industry and are characterized by their lightness, their low thermal and electrical conductivity, and their low humidity absorption coefficient, factors that improve the efficiency of constructions. The results of this study show improvements in the mechanical behavior of the blocks with these plastic additives compared to the traditional ones, along with improvements in the structural behavior of the low (2-story) and medium-height (8-story) frames.

Diabetic Wound Healing with Nanofibers

The most prevalent metabolic illness, diabetic mellitus (DM), is caused by a problem with insulin production. DM promotes the gradual degeneration of pancreatic cells, which raises blood sugar levels. Around 2.1 trillion dollars are invested in global health industries by diabetic wound repair therapies. This is a result of the difficulties that skin ulcers offer in the wound healing process, such as a shortage of macrophage and fibroblast growth factors (TGF-b1 and PDGF, respectively), all of which are required for the production of extracellular matrix (ECM). Nanofibers have been created by electrospinning with large porosity, excellent humidity absorption, a superior oxygen exchange rate, and certain antibacterial properties in response to the growth of medicinal materials and pharmaceutical technology. By including bioactive substances (such growth factors, genes, proteins/peptides, stem cells/exosomes, etc.) and nonbioactive materials, these nanoparticles/hydrogels aid in the healing of diabetic wounds (metal ions, oxygen, nitric oxide, etc.) Due to the slow wound healing process, wound care is a significant biomedical topic that presents difficulties. Malnutrition, insufficient oxygen, smoking, illnesses (such as diabetes and cancer), microbial infections, and other conditions are some of the causes of sluggish wound healing. Currently utilized wound dressings have a number of drawbacks, such as inadequate antibacterial action. Thus, we aimed to go into further depth about the NF (nanofiber) system's aforementioned characteristics for DM complications.

The influence of interfacial failure on the tensile S–N response of aged Arcan joints

AbstractThe strength and durability of adhesive joints are significantly influenced by environmental conditions. Humidity absorption can cause deleterious effects on the adhesive joint's performance. The current study investigates the tensile properties of an epoxy‐based adhesive using Arcan joints (which is a kind of butt joint) subjected to different aging levels and loading conditions. To this end, joints with different aging times, as well as reference‐dried samples, were subjected to both the static and cyclic loading conditions. To construct the S–N curves, different cyclic load levels were applied to the joints. The static results showed that the mechanical properties, such as tensile strength of the joints decreased with an increase of the aging time. The fatigue strength and the fatigue lifetime were significantly decreased by the increase of aging levels, mainly due to an interfacial aging phenomenon. The water diffusion in interfacial aging is faster than that of the adhesive aging, which resulted in a premature failure of the joints for both the static and fatigue conditions. Based on the experimental results, the interfacial diffusion coefficient was calculated using an inverse method. According to the results, the rate of water uptake along the interface is more than 30 times higher than that which occurs in the adhesive.

Aerosol Light Absorption at 1064 nm: Pollution Sources, Meteorological Parameters and Gas Pollutants in Qingdao Coastal Area, China

A two-month sampling campaign was carried out from 1 November to 30 December 2019, to investigate the light absorption of aerosols at coastal sites in Qingdao. The average values and standard deviations of the absorption coefficient (OAC) at λ = 1064 nm during the measurement period were 18.52 ± 13.31 Mm−1. Combined with the backward trajectory model, the aerosol absorption coefficient and gas pollution concentration of six possible air mass trajectories were obtained and calculated. The maximum absorption coefficient of local air masses was approximately 20.4 Mm−1 and anthropogenic pollution originated from mainly local sources in the Jiaozhou area. In our measurements at this site, the results also showed that there was a positive correlation between relative humidity (RH) and aerosol absorption. Without considering other factors, the size of aerosol particles grew with the increasing of RH, which changed the nonlinear relationship between the size and the absorption cross section of aerosol particles subsequently. In addition, the correlations between gas pollutants and OAC were calculated. The atmospheric environment is complex in sea–land intersection areas, especially in coastal cities. Analysis of various aerosol sources, meteorological conditions, and gas precursors enhances the study of aerosol optical absorption.

Reaction-inhibited interfacial coating between PEDOT:PSS sensing membrane and ITO electrode for highly-reliable piezoresistive pressure sensing applications

BackgroundPoly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS) is a promising conductive polymer for the flexible piezoresistive pressure sensor. However, intrinsic hydrophilicity is detrimental to its structural stability under moisture. The present study aims to enhance piezoresistive pressure sensors' stability to achieve the highly-reliable electronic device applications. MethodITO/PEDOT:PSS/ITO piezoresistive pressure sensors with an interdigitated electrode (IDE) structure and different metallic interfacial layers were fabricated. Au layer was introduced between PEDOT:PSS sensing membrane and indium tin oxide (ITO) electrode as a reaction-inhibited interfacial coating of piezoresistive pressure sensors. Significant findingsAfter a measurement time interval of 6 months, the interface reaction suppressed significantly, resulting in low sensitivity deviation (9.22%) and improved durability (400 cycles). The devices are completely sealed using polyethylene terephthalate packaging, avoiding humidity absorption in PEDOT:PSS films successfully. The packaged ITO/PEDOT:PSS/ITO piezoresistive pressure sensors with a double-sided 10-nm-thick Au interfacial layer is a promising candidate for use in highly reliable pressure sensing applications.

Cellulose nanofibrils reinforced PBAT/TPS blends: Mechanical and rheological properties

Poly(butylene adipate-Co-terephthalate)/thermoplasticized starch PBAT/TPS blends are among the most produced biodegradable plastic for wide application packaging, sharing more than 20% of the global production capacity of bioplastics. However, this class of material suffers from poor mechanical strength in comparison of neat PBAT, especially when the TPS content exceeds 30 wt%. Aiming at enhancing the mechanical performance of PBAT/TPS blends while maintaining relatively high TPS content, cellulose nanofibrils (CNFs) was incorporated into the TPS phase using twin screw extrusion. The effects of CNFs content on the microstructure, mechanical properties, melt-rheology and humidity absorption were investigated. An enhancement in the tensile strength and modulus was noted with the inclusion of CNFs, with optimal performance attained at 8 wt% of CNFs. A narrowing in the distribution of the TPS nodules within the PBAT matrix was also observed with the addition of CNFs, which is expected to be on the origin of the main evolution in the mechanical, rheological and humidity observed. Because of the availability of CNFs, biodegradability and facile processability, the ternary PBAT-TPS-CNFs blends might contribute to improve the performance of this class of biodegradable bioplastic.

Sepiolite-zeolite powder doped with capric acid phase change microcapsules for temperature-humidity control

A composite material with temperature-humidity control functions was prepared by using sepiolite-zeolite powder as humidity control matrix and capric acid phase change microcapsules as temperature control material. The micromorphology, thermal conductivity, compressive strength, hygrothermal effect were studied by environmental scanning electron microscope (ESEM), thermal conductivity test, strength test and hygrothermal effect test, respectively. The results showed that the phase change temperature of capric acid phase change microcapsule is between 31 °C ~ 32 °C, the phase change enthalpy is 123.91 J/g, and it has good thermal stability. The humidity control performance is the best and the maximum humidity absorption rate is 6.28% when sepiolite-zeolite powder ratio is 9:1. The humidity control matrix@CAM (Capric acid microcapsules) can control the relative humidity of the environment at 51.74 ~ 58.54% and reduce the temperature fluctuation range by 2 °C ~ 3 °C. Capric acid phase change microcapsules are embedded in the interlaced sepiolite and zeolite powder to form a frame space body which produce capillary condensation adsorption and surface adsorption, absorb and desorb heat through phase changes, thus giving humidity control matrix@CAM a good temperature-humidity control performance.

The Effects of the Solvent Choice of the Continuous Phase on the Poly(Urea-Urethane) Microcapsules Properties

Xylitol, a natural crystalline polyol, presents a cooling effect due to its negative heat of solution at 35 °C supported by humidity absorption, contributing to a fresh sensation when it dissolves. Since this material is sometimes in a liquid state, it cannot be incorporated in or onto a substrate without being protected. One of the strategies to protect the active substance may be forming a barrier layer at its surface, i.e., microencapsulation. The present work is devoted to studying the effect of continuous phase parameters affecting on encapsulation of xylitol with a poly (urea-urethane) shell through a two-step microencapsulation process. The first step is liquid-liquid dispersion either in toluene or Miglyol 812N, and the second step is microencapsulation by interfacial polymerization. The process can be used to control the size distribution of the microparticles, the thickness, and the chemical nature of the shell, which influences the release rate of the active substance. The choice of the continuous phase solvent (toluene or Miglyol 812N) required some changes in the formulation of the system, especially the HLB of the surfactant mixture, to obtain a stable emulsion with a narrow particle size distribution. The thermo-chemical and morphological characteristics of microparticles were studied by Fourier transform-infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), enthalpy of dilution, and scanning electron microscope (SEM). The microparticle size is governed by the emulsion step and the chemical composition of the organic phase. Most of the thermal properties are related to their porous structure and their chemical shell formation during the interfacial polymerization step.

Phenol Novalac Epoxy-modified unsaturated polyester hybrid networks by Silica Nanoparticles/ and Cross linking with Silane Compounds

In this study epoxy phenol novalac resin which consists of silica nanoparticles and unsaturated poly ester resin linked to the Silane and cross linking to that structure and also parameters affecting the processes involved have been evaluated. Cross linking in phenol novalac epoxy resins effects on many properties such as thermal, electrical, mechanical and chemical attributes especially in elevated temperatures. Silane cross-linking’s in phenol novalac epoxy resin with respect to other methods like proxiding, irradiation and utilization of Azo compounds, looks to be a very simple and low cost route, which makes it very encouraging for various industries. Unsaturated poly ester resin is compatible with phenol novalac epoxy resin and also creates some cross-linking and as far as tri methoxy Silane is added to the mentioned resin, its thermal, physical and mechanical properties are optimized. In this literature impact, tension, glass transition temperature, humidity absorption, FTIR and Scanning electron microscopy (SEM) tests were done and the results revealed that as the cross-linking occurs, tension in rupture region increases. This increase is more common at elevated temperatures. The growth in content of silica nanoparticles leads to a drop in water permeability of phenol novalac epoxy resin nanocomposite which contains unsaturated poly ester resin.

Mechanical and Non-Destructive Testing of Plasterboards Subjected to a Hydration Process.

The aim of this study was to investigate the effect of plasterboards’ humidity absorption on their performance. Specimens’ hydration procedure consisted of consecutive immersing in water and subsequent drying at room temperature. Such a procedure was performed to increase the content of moisture within the material volume. The microstructural observations of five different plasterboard types were performed through optical and scanning electron microscopy. The deterioration of their properties was evaluated by using a three-point bending test and a subsequent ultrasonic (ultrasound testing (UT)) longitudinal wave velocity measurement. Depending on the material porosity, a loss of UT wave velocity from 6% to 35% and a considerable decrease in material strength from 70% to 80% were observed. Four types of approximated formulae were proposed to describe the dependence of UT wave velocity on board moisture content. It was found that the proposed UT method could be successfully used for the on-site monitoring of plasterboards’ hydration processes.

A comparative study on epoxy based composites filled with pineapple/areca/ramie hybridized with industrial tea leaf wastes/GFRP

Human beings have been strongly aware of environmental degradation, noise pollution and its human health implications as a result of the unprecedented use of synthetic fibres. The search is to develop a new class of material using eco-friendly fibers extracted from the environmental and industrial wastage which is to be better alternative for existing green composites. In this work, an industrial tea waste has been considered as filler materials due to its excellent sound absorbing properties. In addition to achieve a comprehensive characterization, sound absorbing properties are also to be potentially tested. In this context, three combinations of three different natural fibers (pineapple, areca and ramie) are hybridized with waste tea (powder form) and GFRP were fabricated by a compression molding process with the combinations of 40% reinforcement and 60% epoxy matrix material in a constant proportion. A hydrophilic content present in natural fibers are transformed to hydrophobic by 5% of alkyl treatment for enhancement of bonding between fiber and matrix phase. Mechanical, chemical, morphological, acoustical, humidity absorption and chemical examinations are done for laminates fabricated. The results are evaluated and compared to establish the possibility of using it as a new material for engineering applications especially in under-floor protection, engine decorative cover for passenger cars, wheel housing and inner door panel in automobiles.

Effect of modified liquid glass on absorption humidity and thermal conductivity of flax fiber slabs

Thermal insulation materials based on vegetable fibers are considered. The results of studies on the microstructure of flax fiber noils using a light microscope and flax fibers using electron microscopy are presented. The complex of studies on the selection of the composition of thermal insulation slabs from flax fibers and flax noils has been conducted to determine the process of absorption of humidity from the air. The humidity absorption of insulants based on flax fibers and flax noils has been determined at a relative humidity of 40–97% using sodium liquid glass and modified liquid glass, as well as «Akotherm flaks» slabs. The thermal insulation slabs water vapor absorption kinetics has also been investigated, taking into account the time parameter. The effect of absorption humidity on the thermal conductivity of the studied materials has been examined; for this purpose, the coefficients of thermal conductivity of materials with the maximum humidity content of insulators were determined. The results of the tests indicate the highest efficiency of thermal insulation slabs made of flax fiber tow compared with insulation materials based on flax fibers and «Akotherm flaks» slabs.

Humidity diffusion through composite material under hydrostatic pressure

This study analyzes the hygrothermal behavior of the polyester/glass fiber composite under the influence of the hydrostatic pressure. The composite material contains filler additive aluminum silicate pigments (ASP 400). It is exposed to humidity on one lateral side, under different temperatures. At high temperature, the humidity absorption kinetics presents a fall, and it is due to the coalescence of the cracks, generated by the stress concentration in the free volume. The augmentation of the hydrostatic pressure, the temperature, and the percentage of filler additives (ASP400) increase the diffusion coefficient and the amount of absorbed humidity. The finite element method is employed to simulate the humidity diffusion process. The comparison between experimental and numerical results proves that the hygrothermal behavior of the polyester/glass fiber can be numerically predicted.

Development of a geotextile coated with latex and used as a protection element on heated surfaces

A lot has been researched today about new energy resources and sustainable materials aiming to decrease the impacts caused on the environment. Materials waste that were previously destined for the trash, are now seen in a different way. This present paper had as purpose the confection of a geotextile using banana tree leaves, in particular, fibers extracted from the stem of the banana tree leaves, which presently, are recognized as one of the strongest cellulosic fibers. As a natural geotextile matrix, latex was used and, subsequently, possible applications for the geotextile were analysed through previous material characterization based on literature. The samples were weaved and covered by latex, thereafter, analysis and verification were conducted on the main physical-chemical properties and also mechanical and thermal properties. Such results were obtained through tests, as: tensile properties, flammability, thermogravimetric analysis, water and humidity absorption, moisture resistance, friction, density, weight, biodegradation under environmental conditions. and thermal conductivity. Based on the obtained results, it was possbible to conclude that geotextile can be used as surfaces coating, because beside its high tensile strength, even when heated, the goetextile presentes a low thermal conductivity (0.214 W/mK). That fact means that the material has good thermal characteristics, quality of an isulator. Also, it was conclude that the natural composite has combined properties from banana tree fibers (as thermal properties and mechanical strength) and from thermoplastic elastomer latex. Such result did not compromise the hygroscopicity of the banana fiber. Finally, it could be concluded that the material is sustainable, does not damage the environment and fulfil the coating function, as expected.

Experimental study of an air humidity absorption cycle based on the MHI

An office drinking water cooler is converted to a humidity absorption device. The reservoir-type evaporator of the water cooler is separated, and a finned-tube evaporator is installed. A channel is installed at the inlet of the evaporator. A fan, a cool-mist humidifier, and a heater are installed inside this channel, where the amount of humidity and heat production can be adjusted. Several pressure gauges are installed at different locations of the cycle and monitor cycle performance while working. Pressure variations in different locations of the cycle are measured at various inlet air conditions. The MHI is defined as the ratio of condensation enthalpy to the total given heat. Changes of this index are evaluated by changing the input conditions. Results show that with increasing the air temperature, the condenser and evaporator pressure increases. Results of absorbed water in various MHIs show that with increasing this index, the amount of absorbed water increases. The graph of the absorbed water based on the MHI can be used to estimate the amount of water collected from this device under different climatic conditions. The amounts of collected water from this device for several different cities of Iran are presented. Results show that in high MHIs for a device with a quarter horsepower, the water production rate can reach to 250 g h−1. Also, if the device is working continuously in these conditions, it can produce about 4 kg of water per day.

Indicator Wso: A New Parameter for Characterization of Protective Coating Efficiency Against Humidity

This paper concerns the development of Wso, an indicator of the efficient protection against humidity, as a new parameter characterizing protective coatings. This indicator determines to what degree the covering of cores and sand molds influences, advantageously or disadvantageously, the humidity absorption from surroundings into surface layers, in comparison with layers without covering, which absorb the moisture at high-humidity conditions of atmospheric air. Simultaneously, this indicator will allow for an efficient comparison of tendencies of individual coatings for moisture sorption depending on the number of their layers. Thus, it can serve as a guideline in selecting the coating type for the molding sand on which it will be deposited, while taking into account the time of waiting—of molds and cores covered with coatings—on pouring with liquid metal and the atmospheric conditions to which they will be exposed.

Polymer based optical humidity and temperature sensor

Humidity control and moisture measurements have a wide range of applications like monitoring humidity in food storages, chemical plants, electronic instruments, building constructions, hospitals, museums and libraries. In this work we have developed a fully optical humidity sensor. The device is based on a hygroscopic polymer, polyimide, which undergoes reversible volume expansion on exposure to the humid environment. Multiphysics tool, COMSOL, is used to investigate the mechanism of humidity absorption by the polymer layers. Moisture absorption and diffusion into the polymer layers are modeled and simulated. The sensor is designed using fiber Bragg grating (FBG) developed along an optical fiber. Layers of the polyimide coated the FBG. The induced strain caused by polyimide expansion and deformed geometry of the fiber is modeled. To develop a high sensitive sensor, a π-phase shifted fiber Bragg grating (π-PSFBG) is selected as a sensing element because of its sharp spectrum signal. To further improve the spectral signal, an optimum apodization function is implemented in design of the device. The spectral signal of sensing element is modeled and simulated using mathematical analysis in MATLAB. The results of theoretical modeling are used to fabricate the sensor containing two 24-mm long π-PSFBGs separated by 12 mm on a SMF 28 fiber. A distributed feedback laser scanner is used to characterize the device precisely. The sensor response to the changes in the humidity and temperature of the environment is studied. The experimental results are relatively in good agreement with those obtained theoretically.

An ultrasensitive acoustic wave resonator device enabled by gluing a replaceable micropillar film

Traditional acoustic wave based sensing devices such as quartz crystal microbalance (QCM) rely on the thin films coated on the piezoelectric substrates as the sensing films for chemical and biological detection. This study demonstrates that significant sensitivity enhancement over traditional film based QCM (QCM-F) devices can be achieved by simply attaching a poly(methylmethacrylate) (PMMA) micropillar film onto a QCM substrate (QCM-P) by using a UV-curable glue. Humidity absorption measurements shows that the unique resonance occurred between the micropillars and the piezoelectric substrate improved the mass sensitivity of the QCM sensor by more than eight-fold. In addition, the newly developed QCM-P sensor and traditional QCM-F were utilized to detect bovine serum albumin (BSA) protein immobilization on PMMA surfaces. It was found that the glued QCM-P was capable of measuring BSA at a much lower concentration (200 nM) in comparison to QCM-F (1500 nM). The glue-based micropillar QCM device showed great potential for improving the sensitivity, simplifying the fabrication process, and reducing the cost of QCM sensors for various biosensing and chemical usages.