Water Vapor Resistance Research Articles

Preparation of Cross-Linked Cellulase Aggregate and Application to Cool Finishing of Cotton Fabric

Cellulase was immobilized by cross-linked enzyme aggregation to improve the stability of cellulase. The prepared cross-linked cellulase aggregates (CLCAs) and ice silicone oil were used for the cool finishing of cotton fabric. The results showed that the CLCAs extended the cellulase stability compared to free cellulase. The surface softness, smoothness, moisture permeability, and air permeability of the cotton fabric increased after CLCAs and ice silicone oil treatment. Shearing rigidity of the treated sample was 0.44 cN/(cm·deg), bending rigidity was 0.0069 cN cm, and the drape coefficient was 29.3%. Coefficient of kinetic friction of the treated sample was 0.186. The capillary effect of the treated fabric was 12.1 cm/(30 min). Air permeability was 354.3 L/(m2·s). Moisture penetrability was 3.912 g/(m2·d). The thermal and water-vapor resistance were 0.0194 m2·°C/W and 4.691 Pa·m2/W, respectively.

The Effect of Cement Addition on Water Vapour Resistance Factor of Rammed Earth.

The article aims to determine the effect of cement addition on the water vapour resistance factor of stabilized rammed earth. Literature analysis indicates that different earthen materials show large differences in water vapour resistance factor values. The high diffusion resistance of concrete concerning other construction materials suggests that cement will be one of the factors significantly affecting these values. The paper presents water vapour resistance factor test results of rammed earth with various soil particle sizes and cement contents. The obtained results showed that an increase of cement addition increases the diffusion resistance of the material. However, the diffusion resistance of cement stabilized rammed earth is still low compared to concrete.

Thermal and moisture behavior of a multi-layered assembly in a pneumatic compression device

The objective of this research was to determine the effect of multiple layers of materials typical of those used in air pneumatic compression devices (which require air impermeable layers to function) on thermal and water vapor resistance. The experimental set-up included: (a) single layers of two next-to-skin knit fabrics in both relaxed and extended conditions, (b) two layers of silicone, and (c) a multi-layered assembly comprised of a next-to-skin fabric and two layers of silicone. Structural properties (thickness, mass) dominated thermal resistance of the multi-layered assembly, and the silicone layers rendered this assembly impermeable to water vapor as expected. Results confirmed the need for some form of 'ventilation' to facilitate water vapor transfer from a potential user’s skin to the environment. By creating 18 circular vents across the silicone layers (each vent 314 mm2), which formed ventilation of ∼2% of total surface area, the water vapor resistance of the multi-layered assembly dropped significantly from very high (but non-measurable) to below ∼300 m2 Pa/W, although ventilation did not improve the thermal resistance of the multi-layer arrangements. Results of this research will enable manufacturers of pneumatic compression devices to develop devices comprised of a multiple layer arrangements i.e. a knit fabric next-to-skin layer and silicone layers with optimized vents across the silicone layers, so that the user can continue the compression treatment with an acceptable microenvironment.

A strategy for constructing highly efficient yolk-shell Ce@Mn@TiOx catalyst with dual active sites for low-temperature selective catalytic reduction of NO with NH3

In this work, Ce@MnOx catalysts with core-shell structure were obtained via simple hydrothermal treatment, and the redox capacity can be effectively improved through co-existence of Ce and Mn. Since the strong oxidation capacity of MnOx can lead to the peroxidation of ammonia, the redox capacity can be suppressed with the decrease of manganese content. However, in the case of low manganese content, it is discovered that the surface acidity is very weak and the ammonia adsorption behavior on the catalyst is limited, which is detrimental to the NH3-SCR process. To solve this problem, a series of yolk-shell structured Ce@Mn@TiOx were accordingly constructed, where the TiO2 shell can provide more surface acid sites to promote the adsorption and activation of ammonia. As expected, the Ce@Mn@TiOx exhibits excellent catalytic performance for NH3-SCR at low temperature and possesses a relatively wide working temperature window. More importantly, the TiO2 shell could protect the active sites from water vapor competitive adsorption as well as sulfur attack. Thus, the Ce@Mn@TiOx-10% catalyst exhibited satisfied water vapor resistance in the SCR process, and its sulfur tolerance was also improved to a certain extent. In situ DRIFTs analysis demonstrated that the Ce@Mn@TiOx-10% catalyst mainly follows the L-H reaction mechanism. Consequently, the separation of acid and redox sites has been successfully accomplished by the construction of Ce@Mn@TiOx with yolk-shell structure, where the outer shell (TiO2) mainly enhanced the adsorption capacity of ammonia and protected active centers from attacking by moisture and even sulfur species, while the MnOx interlayer enhanced the interfacial electronic interaction of Ce/Mn and ensured efficient redox cycle during the NH3-SCR process.

Impact of surface waterproofing on the performance of brick masonry through the moisture exposure life-cycle

Moisture is one of the major causes of damage to building systems, affecting the hygrothermal performance and durability of building systems. Surface treatment products are available in the market that can influence the hygric performance of masonry facades under water exposure. These are of a wide range of chemical compositions, and they claim to waterproof the masonry surfaces while not diminishing vapour transmissibility. This paper presents and discusses the findings from a series of benchtests carried out to measure hydrophobicity, water absorption and water vapour transmission following the relevant codes for an appraisal of the hygric behaviour change in brick masonry induced by waterproofing through three distinct phases of the life-cycle of moisture exposure, i.e. first contact with water, wetting and drying. To this end, 4 waterproofing products including silane/siloxane blend liquid and cream, and acrylic and stearate-based liquids were selected for testing, along with 3 brick types common in the 50s and 60s to be representative of the majority of the UK building stock. The findings show that the treatment products indeed enhance the surface hydrophobicity and reduce water absorption while allowing water vapour transmission to differing degrees: silane/siloxane blend cream overall was found the most effective throughout the moisture-exposure life-cycle, with an average of ~96% reduction in water absorption and 18% of increase in water vapour resistance in comparison to the untreated case, followed by the stearate-based liquid with 57% reduction in water absorption and 12% increase in water vapour resistance. The acrylic-based product demonstrated good performance in hydrophobicity and water vapour transmission tests, however led to a comparatively higher water absorption capacity than the other treatment products with only ~40% reduction in comparison to the base-case. Finally, silane/siloxane blend liquid was found to lead to the lowest contact angle, demonstrating a lower-than-others capacity to developing surface hydrophobicity, and led to 35% reduction in water absorption and 28% increase in water vapour resistance, making it the poorest product in the dataset to lead to watertight and vapour open systems under water exposure. Based on the test results it was also deemed beneficial to use masonry specimens to account for its composite nature, rather than using results obtained from brick and mortar separately to infer the wall response under exposure.

Engineering laminated paper for SARS-CoV-2 medical gowns

The COVID-19 pandemic has highlighted the need for diversity in the market and alternative materials for personal protective equipment (PPE). Paper has high coatability for tunable barrier performance, and an agile production process, making it a potential substitute for polyolefin-derived PPE materials. Bleached and newsprint papers were laminated with polyethylene (PE) coatings of different thicknesses, and characterised for their potential use as medical gowns for healthcare workers and COVID-19 patients. Thicker PE lamination improved coating homogeneity and water vapour resistance. 49 GSM bleached paper with 16 GSM PE coating showed high tensile and seam strength, and low water vapour transmission rate (WVTR). Phi-X174 bacteriophage testing revealed that paper laminated with 15 GSM coating hinders virus penetration. This research demonstrates that PE laminated paper is a promising material for low cost viral protective gowns.

Optimisation of the Sublimation Textile Printing Process Using the Taguchi Method

In this paper, printing parameters for the sublimation printing of polyester fabrics like the number of strokes, the sublimation paper weight in grams per square metre, the fusing temperature and time were optimised using the Tauguchi experimental design technique. In the evaluations the signal-to-noise ratio was used. Sixteen experiments were performed with respect to the L 16 Orthogonal array design for the Tauguchi approach. The results show a considerable improvement in the signal-to-noise ratio as compared to the initial conditions. Through this study, not only can optimum printing conditions for sublimation printed polyester fabrics be obtained but also the significant factors that affect water vapour resistance.

Analysis of the influence of moisture and temperature control according to the combination of porous sediment and MPCM

Indoor finishing materials that can control the indoor environment through moisture control materials are being developed. Since humidity is affected by temperature, it is necessary to analyze a mixture of materials that affect temperature and materials that affect humidity. This study analyzed the effects of absorbent porous sediments (PAS) and micro-encapsulated phase change materials (MPCM) on the indoor environment and on each other's abilities. The effects of each other were compared by varying the mixing ratio of PAS and MPCM. Actually, as the content of PAS increased, it had a high latent heat of 7.939J/g, and the Water vapor resistance factor increased as the amount of MPCM increased. It has proven to affect different abilities. However, since PAS and MPCM have an influence on each other, it does not have a better hygroscopicity control when PAS increases. Dynamic heat and moisture experiments have confirmed that it has an excellent ratio. The excellent ratio in this study was an interior finish with a ratio of 0.35:0.65G and 10% MPCM to PAS.

Heat and moisture transfer properties of a firefighter clothing with a new fire-resistant underwear

Under dynamic wear conditions, moisture management and heat transfer behaviour of clothing between the human body and its environment are very important attributes for comfort and performance. Especially considering heavy works like firefighting, it is important to analyse liquid moisture management and thermal comfort properties of fabrics that influence moisture sensation and personnel comfort feeling significantly. This study mainly investigates thermal comfort and moisture management properties of a firefighter clothing with a new fire resistant underwear. Analysing single layer fabric (underwear, outer shell, moisture barrier and thermal barrier) performance properties, together with their three-layered and four-layered combinations gives a better understanding of comfort and protective performance. For characterizing the fabric structures, weight, thickness, FTIR analysis and SEM-EDX tests were conducted. Heat and moisture transfer properties were measured with limited flame spread, thermal resistance (skin model), water vapour transmission rate (dish method), thermal conductivity, air permeability, thermal diffusion, water vapour resistance, moisture management transfer (MMT) and water vapour permeability tests.

Prediction of air permeability coefficient and water-vapor resistance of 3D textile layer

This study presents a computational model for investigation of the air permeability coefficient and water-vapor resistance coefficient through 3D textile layer. The effective values of the coefficients are highly dependent on the volumetric internal structure of the layer. The computational study of air and water vapor flow has been performed a microscale finite element model of the representative volume of the textile layer by taking into account the real configuration the yarns and filaments. The effective values of the coefficients were obtained by using taking average values of air and water vapor fluxes through the thickness of the representative volume. The steady state computational models in micro scale are based on Navier-Stokes and Brinkman partial differential equations. The simulations were performed in Comsol Multiphysics 5.3a software environment by using laminar flow (.spf) application mode. Numerical results for the air permeability of the samples were obtained, analyzed and validated by comparing against experimental data. Good agreement with experimental data has been achieved. Highlights COMSOL software was used to simulate air permeability and water-vapor resistance of 3D textile layer. The numerical model has demonstrated its efficiency comparing with experimental air permeability measurements.

Analysis of biochar-mortar composite as a humidity control material to improve the building energy and hygrothermal performance

This study suggests a new perspective of biochar as a building material that improve not only for the strength but also hygrothermal properties. Biochar has a high porosity and surface area created by pyrolysis. It can be suitably used as a porous material because porous materials are used by incorporating into building materials for improving hygrothermal performance in the construction sector. To analyze whether biochar can be used as a functional building material to improve the hygrothermal performance, two types of biochar, made from oilseed rape (OSB) and mixed softwood (SWB), were prepared. A biochar-mortar composite was prepared according to the mixing ratio of the biochar from 2 wt% to 8 wt%, and the compressive strength and hygrothermal performance of them were analyzed. The compressive strength is the highest when 4 wt% of biochar into the mortar was mixed regardless of the type of biochar. Thermal conductivity of biochar-mortar composites was decreased as the biochar addition increased, and the value of biochar-mortar composites with 8 wt% OSB decreases by maximum 57.6% compared to the conventional cement mortar. The water vapor resistance factor of biochar-mortar composites increases, and biochar-mortar composites with 8 wt% SWB increases by maximum 50.9% compared to the reference. WUFI simulation shows that the biochar-mortar composites can contribute to a humidity control and no mold growth. The biochar-mortar composites can also contribute to energy savings although the amount of savings is insignificant. As a result, this study proved that when the mortar with biochar addition was possible to improve not only strength but also hygrothermal properties of mortar. This approach will be a new perspective that biochar can apply to the building material in practice.

Mechanical Properties and Water Vapor Permeation of Polypropylene/Hollow Silica Composite

In this study, we modified polypropylene (PP) by using melt-blending hollow silica (HSiO2) with it and to form HSiO2/PP composites. The composites were characterized by mechanical properties, X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). In order to investigate the effect of nanofiller to the barrier property of water vapor, the water vapor transmission rate of PP and HSiO2/PP composites has been tested. The study found that the addition of HSiO2 did not change the crystal structure of the matrix material and there was no chemical reaction. However, the tensile strength of the composite is improved, and the water vapor barrier performance were also improved. When the content of HSiO2 is 0.9%, the tensile strength of the composite is the highest and the water vapor resistance is the best.

Air Permeability and Water Vapor Resistance of Differently Finished Cotton and Cotton/Elastane Single Jersey Knitted Fabrics

ABSTRACT This study investigates the knitted fabrics’ air permeability and water vapor resistance as complex phenomena of the interaction between the fiber nature, fabric structural characteristics and, different wet processes. Bleaching and dyeing together with the content of elastane are the main factors determining fabric structural characteristics. 100% cotton fabrics have a higher intensity of warm/cool feeling since they have higher air permeability than elastane containing fabrics. The air permeability and water vapor resistance of elastane containing fabrics decreased after the wet processes, whereby the bleached knitted fabrics showed higher air permeability and lower water vapor resistance than dyed. Decreased air permeability and increased water vapor resistance of softened elastane containing fabrics are governed by the cationic softener pick-up mechanism. Namely, the cationic softener is deposited on the yarns’ surfaces; its hydrophobic carbon ends repel from each other. This acts as a barrier for air which contributes to an increase in the fabric water vapor resistance. The softened dyed knitted fabrics have lower air permeability and slightly higher water vapor resistance than softened bleached fabrics which may be attributed to the interaction between reactive dyestuff and cationic softener. The comfort properties quality of finished knitted fabrics decreased with elastane incorporation and with softening.

Evaluation of Some Comfort and Mechanical Properties of Knitted Fabrics Made of Different Regenerated Cellulosic Fibres

Knitted fabrics with a wide range of fabric construction varying in fibre type, yarn type is frequently preferred by consumers owing to their high comfort properties. Today new, functional and biodegradable, natural fibre based raw materials are mostly considered for knitted fabrics and clothing designs with a sustainable consumer manner. Collagen peptide added fibres are the recent improved regenerated cellulosic fibres which are known to be providing a skin friendly texture with high thermal and moisture comfort. Within this study, some performance properties such as thermal properties, water vapour permeability, water vapour resistance, air permeability as well as bursting strength of greige and dyed knitted samples made of 100 % Tencel™, Modal, Cupro, Umorfil®, combed cotton and carded cotton yarn were evaluated. ANOVA test was performed for the statistical evaluation of yarn and fabric properties. According to ANOVA results, regenerated cellulosic yarn type of knitted fabrics and the process type (untreated greige fabric or dyed fabric) were generally significant factors on mentioned performance properties of knitted fabrics. The results of experiments also revealed that beside the regenerated cellulosic fibres, new developed collagen peptide added Umorfil® fibre may be used as the raw material of knitted fabrics for sport garments with satisfying comfort results.

Oxidation Performance of Ytterbium Disilicate/Silicon Environmental Barrier Coating via Optimized Air Plasma Spraying

Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiCf/SiC ceramic matrix composites (CMCs) in complex combustion environment, and improve the service life of thermal engine components. In this paper, by adjusting the parameters of atmospheric plasma spraying (APS), the spraying process of ytterbium disilicate (Yb2Si2O7) under a lower power has been optimized. A two-layer EBC system consisting of ytterbium disilicate and silicon is prepared on the SiCf/SiC composite substrate by using optimized technological parameters. The thermal resistance and water oxygen corrosion resistance of such two-layer EBC system are investigated. The results indicate that the current ytterbium disilicate/silicon EBC system exhibits good phase stability, excellent water vapor and oxygen corrosion resistance. However, the exposed silicon bonding layer tends to generate an excessive thermal growth oxide (TGO) layer known as SiO2, leading to an early spallation of the coating.

Investigation of thermal comfort properties of electrospun thermoplastic polyurethane fiber coated knitted fabrics for wind‐resistant clothing

AbstractThe integration of nanofibers into conventional fabrics may open up new opportunities such as improving the comfort performance and thermal management properties of outdoor clothing. Nanofibers are able to form a highly porous mesh and their large surface‐to‐volume ratio improves performance for many applications. This study shows the possible utility of the nanofiber coating on conventional knitted fabrics for improving the wind‐resistance and breathability properties. It was seen that nanofiber coating did not cause a significant effect on water vapor and thermal resistance of electrospun thermoplastic polyurethane nanofiber coated cotton (CO), modal (CMD), viscose (CV), and lyocell (CLY) single jersey fabrics, while resistance to air permeability was increased with the increased nanofiber coating. High level of air resistance was achieved with 30 min of coating. In terms of comfort properties, the nanofiber coating proved to be advantageous due to its lower air permeability with its water vapor permeable structure. However, thermal insulation level of these fabrics was still low and fragile nanofiber layer needed to be protected. Therefore, a multi‐layered fabric form was derived from combination of cotton and lyocell fabrics with a nanofiber layer. The results showed that nanofibers could be used to improve the wind‐resistance and comfort properties of multi‐layered knitted structures.

Synthesis and characterisation of monolithic PTFE‐modified MnOX/FeOX catalysts for selective catalytic reduction (SCR) of NOX at low temperature

AbstractBACKGROUNDSelective catalytic reduction (SCR) of NOX has been the most widely used technique for the reduction of NOX emissions from combustion flue gas. MnOX/FeOX based catalysts typically can attain high NOX conversion at low temperature but with inferior water vapor resistance.RESULTSA MnOX/FeOX catalyst was synthesized by the sonicated co‐precipitation method and then wash‐coated on ceramic cordierite monoliths to form a low pressure drop monolithic catalyst suitable for high flowrate flue gas treatment conditions. The catalyst achieved above 90% NO conversion at a gas hourly space velocity (GHSV) of 30 000 h−1 over a 125–225 °C temperature window under simulated industrial flue gas conditions. In the presence of up to 5% H2O vapor, comparable performance was retained for a reduced temperature window of ≥150 °C. In order to improve water resistance and LT‐SCR performance, an optimal 10% w/w polytetrafluoroethylene (PTFE) doped MnOX/FeOX catalyst was developed, which exhibited remarkably high performance of up to 98% NO conversion, with improved water resistance at up to 10% v/v H2O while retaining high performance from 100 °C.CONCLUSIONMonolithic MnOX/FeOX catalyst incorporating PTFE significantly improved NO conversion and water vapour resistance due to the enhanced NH3 adsorption associated with Lewis acid sites and water repellent property. These findings will provide guidance for researchers in this field to adapt F‐based or similar additives into the making of high performance and high water resistance catalysts either to retrofit existing catalyst synthesis procedures or reinvent a novel catalyst in a scalable but economical way. © 2020 Society of Chemical Industry

Research of Wood Waste as a Potential Filler for Loose-Fill Building Insulation: Appropriate Selection and Incorporation into Polyurethane Biocomposite Foams.

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect which influences the stability of the final products. Therefore, the current study analyses different WW-based fillers as possible modifiers for polyurethane biocomposite foams for the application as loose-fill materials in building envelopes. During the study of WW-based fillers, it was determined that the most promising filler is wood scobs (WS) with a thermal conductivity of 0.0496 W/m·K, short-term water absorption by partial immersion—12.5 kg/m2, water vapour resistance—0.34 m2·h·Pa/mg and water vapour diffusion resistance factor—2.4. In order to evaluate the WS performance as a filler in PUR biocomposite foams, different ratios of PUR binder and WS filler (PURb/WS) were selected. It was found that a 0.40 PURb/WS ratio is insufficient for the appropriate wetting of WS filler while a 0.70 PURb/WS ratio produced PUR biocomposite foams with the most suitable performance: thermal conductivity reduced from 0.0523 to 0.0476 W/m·K, water absorption—from 5.6 to 1.3 kg/m2, while the compressive strength increased from 142 to 272 kPa and the tensile strength increased from 44 to 272 kPa.

Water vapor resistance measured on sweating thermal manikin and Permetest skin model in the vertical orientation

This paper is a comparison of water vapor resistance (Ret) measured using the Permetest skin model and Tore sweating thermal manikin, i.e. 2D versus 3D methods; and to study the relationship between them. Three materials and five air gap distances were used for the measurement between these two devices, the test conditions in the climatic chambers were set up according to the ISO standard of each measurement method. Results of the correlation coefficient of three materials showed that they all had a strong increasing trend between Permetest and the sweating thermal manikin. From the regression analysis, the P-value of all three materials showed that P< 0.05 and 100% cotton R2=0.83, 50% cotton 50% polyester R2=0.91, 100% polyester R2=0.99. However, Ret resulting values from each device slowed down after 12mm air gap distance.

Evaluation of hygrothermal performance of wood-derived biocomposite with biochar in response to climate change

Wood is a sustainable resource and building material. It provides an excellent response to climate change and has excellent insulation performance. However, structural defects may occur due to decay from moisture, resulting in poor dimensional stability. The rich organic substances contained in wood can lead to mold when the moisture content is consistently high, adversely affecting the health of occupants. Therefore, we attempted to compensate for the disadvantages of wood in regard to water stability while maintaining the high thermal insulation performance and carbon dioxide storage capacity, using biochar from thermally decomposed spruce under oxygen limiting conditions. A wood-derived biocomposite was prepared by mixing biochar and soft wood-based chips using the hot-press method, and the thermal conductivity, specific heat, water vapor resistance factor, moisture adsorption, and moisture desorption performances were analyzed. The thermal conductivity of WB10 with 10 wt% biochar content was 0.09301 W/mK. This is a 7.98% decrease from 0.10108 W/mK, the thermal conductivity of WB0 without biochar. The water vapor resistance factor tended to increase when the biochar ratio increased. As the proportion of biochar increased, the equilibrium moisture content in high relative humidity tended to decrease, and it was found that the moisture adsorption and desorption performances were affected by the ratio of the biochar. Therefore, wood-derived biocomposites using biochar can be used in environmentally friendly materials, with improved thermal insulation performance and water stability.