Vapor Resistance Research Articles

Polylactic acid/lyocell fibre as an eco-friendly alternative to polyethylene terephthalate/cotton fibre blended yarns and knitted fabrics

Polylactic acid (PLA) and lyocell fibres blend can offer an eco-friendly alternative to commonly employed blend of polyethylene terephthalate (PET) and cotton fibres in textiles. PET fibre is non-biodegradable and depletes fossils fuels and adds to landfill sites whereas conventional cotton, dominant part of global cotton production, requires large quantity of water and pesticides during its production. In this study, 100% PLA, 100% lyocell and PLA-lyocell (PL) blended yarns, in varying ratios, were ring spun and subsequently weft knitted and compared with the PET/cotton blend (50/50). The yarns were evaluated for tensile properties while the fabrics were investigated for bursting strength, bending length, pilling propensity, water vapour resistance, thermal resistance and air permeability. The economic comparisons of the two blends were also included. The results indicated that comparatively PL blends (in particular lyocell fibre rich blends) can offer environmental and performance advantages compared to PC blended knitted fabrics for casual summer clothing and active wear.

Properties of multifunctional lightweight mortars containing zeolite and natural fibers

The article focuses on the development of innovative and multifunctional mortars with low environmental impact for indoor applications acting as passive systems to moderate extremes of humidity and to lower the concentration of pollutants. Mortars are manufactured by keeping constant the water/binder ratio, using sand as reference aggregate, and by replacing the total volume of sand with zeolite. In some mixes the aggregate, is also at 25vol% by wool natural fibers. Regardless lightness, zeolite thanks to its pozzolanic activity, helps to improve the compressive strength of mortars manufactured with wool fibers. In addition, the combination of zeolite and wool increases the hygro-thermal performance of mortars: water vapor resistance factor (22% lower than the reference), moisture buffering value (100% higher than the reference), and thermal conductivity (66% lower than the reference), respectively. Depolluting properties of zeolite-based mortars, in terms of adsorption capacity, are 65% lower than that of reference mortar.

Hygrothermal performance of vernacular stone in a desert climate

Remote desert communities are often the most vulnerable to temperature extremes, as lack of access to reliable electricity prevents the use of active cooling or heating. Hence, there is a need to investigate how the building envelope itself can be used to passively regulate indoor environments. Readily available vernacular building materials in such areas are thought to aid in not only attenuating temperature swings but also moisture regulation, which improves comfort in a dry climate. Thus, the aim of this research is to investigate the hygrothermal properties of three different stone types commonly used as building materials in the Western Desert of Egypt: sandstone, limestone and, uniquely, Karshif, a rock rich in sodium chloride. The materials’ thermal conductivity, moisture sorption and buffering, water vapour resistance, porosity distribution and phase composition are experimentally investigated. Our results show that the local perception of limestone buildings having poor indoor comfort, despite the material’s superior thermal conductivity and specific heat capacity is only explainable through the relative superiority of sandstone and Karshif in moisture buffering. Vernacular materials need to be tested in environmental conditions representative of their local climate, rather than standardised conditions, as the latter may paint an incorrect picture of performance which, in the case of Karshif, led to partial dissolution under relative humidity of greater than 80%. However, testing under typical desert conditions demonstrates that both Karshif and sandstone are viable building materials that exhibit excellent moisture regulation behaviour. Since building materials in desert conditions may have to withstand atypical weather extremes, including rain, local materials need to be utilised within carefully designed wall assemblies or treated wall sections and, in the case of Karshif, not used in areas where relative humidity regularly reaches 80%. These findings are an important contribution in validating the performance of vernacular stone, and more widely, in demonstrating the importance of selecting appropriate testing conditions.

Incorporation of Very Insoluble Monomers in Waterborne Coatings

AbstractThe benefits of polymerizing very insoluble monomers in aqueous media, avoiding the use of energy‐intensive procedures, by implementing two novel synthesis techniques based on the emulsifier combination in emulsion polymerization and on miniemulsification by phase inversion temperature are investigated. The performance of standalone polymers consisting of monomers, namely lauryl methacrylate, isobornyl acrylate, and 1H,1H,2H,2H‐perfluorodecyl acrylate, and of formulated binders with these monomers incorporated either through blending or in situ polymerization, is evaluated with special emphasis on their water‐barrier properties (e.g., uptake, whitening, immersion, and vapor resistance) and on their chemical resistance. The performance of the standalone polymers is found to be similar to that of polymers prepared by high‐shear miniemulsion polymerization, while the performance of the formulated binders is generally superior to a commercial coating formulation based on a binder recommended for water resistance.

UTILIZATION OF SUPERABSORBENT POLYMERS IN PLASTERS FOR MODERATION OF INDOOR RELATIVE HUMIDITY LEVEL

Nowadays, the energy efficiency and moderation of indoor environment of buildings became important topic in the field of building physics. Moisture occurrence in building construction poses a significant task for building designers and material engineers. Among other factors, a high level of relative humidity has negative effect on the work efficiency and health of building inhabitants. The presented paper is aimed on the analysis of chosen superabsorbent polymers (SAPs) and its influence on properties of newly developed interior plasters. The identification of optimal ratio between superabsorbent polymers and plaster mixture from the point of view of the workability of fresh mixtures is done. Also, the effect of water/dry mixture ratio is studied according to enhanced absorption capability of SAPs. Specific attention is paid to hygric properties, the determination of apparent moisture diffusivity, water vapor resistance factor and estimation of sorption isotherms. Obtained results directly point to significant effect of SAP admixture on material properties of developed plasters. Namely, addition of up to 3 wt.% of SAPs shifts the water absorption coefficient almost ten-times, while the total open porosity is increased only about 20%. Such materials can be applied for the damped areas or places where increased water transport parameters play an important role for the efficient moisture removal.

Equiatomic quaternary (Y1/4Ho1/4Er1/4Yb1/4)2SiO5 silicate: A perspective multifunctional thermal and environmental barrier coating material

Equiatomic quaternary (Y1/4Ho1/4Er1/4Yb1/4)2SiO5 solid solution is investigated as a multifunctional thermal and environmental barrier coating (TEBC) material in this work. Dense and pure materials were prepared by hot pressing method, and the compositional homogeneity at macroscale and atomic scale were confirmed by electron-dispersive spectrometer elemental mapping and high-angle annular dark-field images. The quaternary solid solution displays balanced optimal properties on Young's modulus, thermal conductivity, thermal expansion, and high temperature water vapor resistance. The moderate cocktail effects also provide suggestions on the design of rare earth monosilicate TEBC materials.

Numerical Analysis of Thermal and Moisture Bridges in Insulation Filled Masonry Walls and Corner Joints

In recent years, thermal insulation filled masonry blocks have become widespread in Central-Europe. These blocks can satisfy thermal performance requirements without the need of additional insulation. However, these requirements in the building regulations only consider thermal, but neglect moisture aspects. This paper presents a comparative analysis of steady-state numerical conjugated heat- and moisture transport FEM simulations of masonry walls. The hygrothermal material properties of the insulation filled masonry blocks were measured in laboratory. In the paper, besides a wall section, a wall corner joint is presented, both modeled in 2D from complex building elements, such as insulation filled blocks, and were tested using different fillers (aerogel, expanded perlite, expanded polystyrene, mineral wool and PUR foam), respectively. Monthly variation of the fillers’ thermal conductivity, thermal and moisture transmittance and effective water vapor diffusion resistance of the walls, as well as linear thermal and moisture transmittance of the wall corner joints were examined in details. A comparison between detailed and simplified modeling were also carried out. The evaluation of the results shows that there are noticeable differences in trends between thermal and moisture transmittances, latter show significantly greater variation and depends mainly on the hygrothermal behavior of the filler. Based on effective water vapor resistance factors, we showed that assuming the same vapor transmission properties for all type of filled masonry blocks is a mistake.

Investigation of Thermo-Physiological Comfort and Mechanical Properties of Fine Cotton Fabrics for Ladies’ Summer Apparel

ABSTRACT Fine cotton fabrics such as “Lawns” for ladies’ apparel are extremely popular in the subcontinent and all those parts of the world where summers are scorching and the subsequent rainy seasons quite hot and humid. The required fabrics should neither be too thin to be weak nor too thick to be uncomfortable. The main objective of this study was to investigate thermo-physiological comfort and mechanical properties of cotton fabrics ranging from approx. 50 to 80 g/m2 areal densities (GSM) using 80, 70, 60, and 50 Ne yarn counts and to determine optimum fabric parameters for good fabric comfort and strength. Fabric of a specific areal density could be developed either by using coarser yarn counts with lower number of ends and picks per inch or by using finer yarn counts with higher number of ends and picks per inch. Results show that fabric of a specific areal density produced from coarser yarns with lower number of ends and picks results in better fabric air permeability and better tear strength, as compared to that made from finer yarns with higher number of ends and picks per inch. However, fabric thermal and water vapor resistance are not significantly affected by either approach used for the range of fabrics produced in this study. Based on response surface optimization, the optimum fabric parameters were found to be 60 Ne warp count, 50 Ne weft count, 90 ends/inch and 50 picks/inch for simultaneously achieving good fabric air permeability and strength properties.

Development of wood-lime boards as building materials improving thermal and moisture performance based on hygrothermal behavior evaluation

Currently, wood is attracting attention as an eco-friendly building material that has advantages such as high insulation performance and low CO2 emission. However, it is vulnerable to moisture. Therefore, the objective of this study was to develop wood-lime boards using lime as resins that is known to be excellent in moisture control. Hygrothermal behaviors of such wood-lime boards were then analyzed to confirm their applicability as building materials. Results of hygrothermal behavior analysis revealed that they had higher insulation performance and higher water vapor resistance factor. Simulation analysis results also indicated that both total water content and mold growth risk were reduced when wood-lime boards were used in comparison with existing layers. Therefore, wood-lime boards were applicable as building materials.

Water vapour and grease resistance properties of paper coating based starch-bentonite clay

In the present study, the water vapour and grease resistance properties of paper coating based starch – bentonite clay has been investigated. The clay concentration was 0%, 10%, 15%, 23%, 30%, 40% dan 50% w/w. The composites were prepared by solution casting and coated on the surface of the paper, and analysed using Payne cup method (water vapour transmitter rate-WVTR), grease resistance test and X-Ray diffraction (XRD).The WVTR results showed that the addition of clay improved water vapour barrier properties and the most optimal improvement was obtained at clay concentration in the range of 10 - 23 wt %. However, the opposite trend was observed for grease resistance properties which showed that the grease resistance decreased with increasing clay concentration. XRD results showed that starch entered clay gallery and formed intercalated bilayer structure both at clay concentration of 10 and 23 wt % wt. The clay/starch composite (23 wt%) was more ordered and higher amount of starch chains entered gallery than than those of clay/starch (10 wt%) supporting better water barrier properties at high clay concentration.

Preparation and characterization of multilayer films composed of chitosan, sodium alginate and carboxymethyl chitosan-ZnO nanoparticles

To deal with serious environmental pollution resulting from plastic packaging materials, biodegradable films using chitosan (CS) are gaining considerable increase gradually. However, chitosan films lack important properties to meet the preserved demands. This study aimed to develop new bio-based films incorporated with carboxymethyl chitosan-ZnO (CMCS-ZnO) nanoparticles and sodium alginate (SA) to overcome the weakness of CS films. CMCS-ZnO nanoparticles were successfully synthesized in the matrix of CMCS through direct precipitation method, which showed an average diameter of 100 nm. Multilayer films with CS film as the outer layer and SA film as the inner layer were prepared by solution casting method. The addition of CMCS-ZnO nanoparticles led to enhanced tensile strength, and to better water vapor resistance. The as-prepared films exhibited distinctive antibacterial activity against S. aureus and E. coli. The results suggested that the as-prepared film is expected to be a promising material for food packaging.

A computational fluid dynamics analysis of the effects of size and shape of anterior nasal septal perforations.

Nasal septal perforations (NSPs) often cause bleeding, crusting, obstruction, and/or whistling. The objective was to analyze the impact of anterior NSP size and shape on nasal physiology using computational fluid dynamics (CFD). A 3-dimensional model of the nasal cavity was constructed from a radiologically normal CT scan using imaging software. Anterior NSPs (ovoid (ONSP): 0.5, 1, 2, and 3 cm long anterior-to-posteriorly and round (RNSP, 0.5 and 1 cm)) were virtually created in the model and divided into ventral, dorsal, anterior, and posterior regions. Steady-state inspiratory airflow, heat, and water vapor transport were simulated using Fluent CFD software. Air crossover through the perforation, wall shear, heat flux, water vapor flux, resistance, and humidification were analyzed. Air crossover and wall shear increased with perforation size. Regionally, wall shear and heat and water vapor flux were highest posteriorly and lowest anteriorly, generally increasing with size in those regions. RNSPs had greater heat and water vapor flux compared to corresponding size ONSPs. Resistance decreased by 10% or more from normal only in the 3 cm ONSP. Maximum water content was achieved more posteriorly in larger NSP nasal cavities. High wall shear and heat and water vapor flux in posterior perforation regions may explain the crusting most commonly noted on posterior NSP edges. This preliminary study suggests that larger NSPs have a greater effect on nasal resistance and water content. Decrease in resistance with larger NSP size may be implicated in reported symptomatic improvement following enlargement of NSPs for treatment.

Analysis of thermal properties, water vapor resistance and radiant heat transmission through different combinations of firefighter protective clothing

This experimental work is an effort to seek the possibility of improvement in thermal protective performance of firefighter protective clothing at different levels of heat flux density. Improvement in thermal protective performance means enhancement in the time of exposure against the heat flux, which will provide extra time to firefighters to perform their duties without suffering from severe injuries. Four different multilayer combinations of firefighter protective clothing were investigated. Each combination consists of outer shell, moisture barrier and thermal liner. Aerogel sheet was also employed as a substitute to thermal barrier. Initially, properties like thermal resistance, thermal conductivity, and water vapor resistance of multilayer fabric assemblies were investigated. Later on these combinations were exposed to different levels of radiant heat flux density i.e. at 10, 20 and 30 kW/m2 as per ISO 6942 standard. It was noted that those combinations in which aerogel blanket was used as thermal barrier acquire greater thermal resistance, water vapor resistance and have less transmitted heat flux density values.

EVALUATION OF ANTIBACTERIAL, MECHANICAL, AND COMFORT PROPERTIES OF WOVEN FABRICS CONSIST OF COTTON, BAMBOO, AND SILVER FIBERS

In this study, experimental and statistical evaluation of antibacterial, mechanical, and comfort properties of woven fabrics consisting of cotton, bamboo and silver yarns were presented. For the purpose of the study; cotton-bamboo and cotton-silver blended fabrics were produced, mechanical properties (such as tensile strength and tear strength) were investigated, antibacterial activities were determined, and thermal comfort properties (such as thermal conductivity, thermal absorption, thermal resistance, air permeability, water vapor permeability, and water vapor resistance) were measured. Statistical evaluations were performed by one way ANOVA and Tukey HSD and Tamhane’s T2 test methods. According to the outputs of the research, the mechanical and comfort properties can be improved and the antibacterial activities can be obtained of shirting and bedding fabrics by differing weft yarn type and density.

Numerical analysis of hygrothermal properties and behavior of Korean based cross-laminated timber (CLT) wall system to deduce optimal assemblies

Cross Laminated Timber (CLT) is attracting worldwide attention, due to its durability, usability, and many other advantages. However, since CLT is made of timber, analysis of the hygrothermal performance is essential. In this study, the basic hygrothermal values are measured to obtain the exact hygrothermal performances. The values are put into the simulation with various assemblies which has hygroscopic effects. The effectors are the type of insulation, the presence of the vapor retarder, the climate condition and the type of standards. The final goal of this paper is to find the optimal CLT assemblies. The thermal conductivity, thermal transmittance coefficient, and water vapor resistance factor were measured. The thermal transmittance coefficient of the wall system was measured by using TCi and facing thermo-hygrostat, and applied in the simulation. The water vapor resistance was measured by conducting dry-cup test. In addition, the various conditions that affect the thermal moisture behavior were applied to the simulation for getting stable hygrothermal results. As a result, the standard of Passive house and Domestic wooden house, the climate condition, the presence of breathable water proofing paper, and the insulation alternatives of Expended Polystyrene (EPS) and Extruded Polystyrene (XPS) were applied. It was concluded that breathable waterproofing paper should be installed inside, and the applications of both XPS and EPS made no difference to moisture but the application of Mineral Wool was adversely affect to hygrothermal performance of the CLT wall system. The thickness of insulation should be designed according to the Passive house standard (0.15 W/m2K) rather than the Domestic (Korea) Wooden house standard (0.21 W/m2K).

On the Thermal and Pressure Characteristics of Sport Compression Garments

In this study, various knitted fabric structures were designed to help preventing muscular difficulties in sports. The samples, containing channels in widthwise direction, were produced by jacquard knitting technique. The effects of channel size and quilted inlay design were investigated in terms of pressure behaviour, thermal and water vapour resistance. Increasing of channel size and adding inlay yarns provided higher thermal resistance, as well as an increase in water vapour resistance, they also significantly affected pressure characteristics of samples.

A lotus effect-inspired flexible and breathable membrane with hierarchical electrospinning micro/nanofibers and ZnO nanowires

Hierarchical structures such as the leaf of lotus are promising models for self-cleaning surfaces. A biomimetic structure that contains PVDF microfibers (ZnO nanowires covered with oleic acid) was prepared here to illustrate the biomimetic lotus effect concept. This was prepared via electrospinning, hydrothermal synthesis, and dip coating. The hierarchical structure and oleic acid coating was shown to contribute to super hydrophobicity with a water contact angle (WCA) > 150°. The super hydrophobic flexible membrane not only exhibited water droplet bouncing and rolling behaviors, but also demonstrated promising self-cleaning properties, water resistance, and permeability of air and water vapor. These characteristics have far reaching implications in broadening the application of the self-cleaning textiles, waterproof breathable membrane, medical devices, and surgical plants such as artificial blood vessels.

Analysis of walls of functional gypsum board added with porous material and phase change material to improve hygrothermal performance

Gypsum board is widely used as a finishing material, and it is mixed with functional materials to improve the comfort level of indoor air, provide thermal insulation, and satisfy moisture properties. In addition, Phase change material (PCM) is also used as a functional material to reduce energy consumption. Recently, there have been many studies on improving moisture problems, such as condensation and mold growth. Therefore, the hygrothermal behavior of building materials must be carefully considered to reduce the risk of moisture problems. The objective of this study was to improve the thermal and moisture performance of gypsum board, and achieve energy savings by adding porous material and PCM. The characteristics of functional gypsum board (FGB) with expanded vermiculite (EV), expanded perlite (EP), nano carbon material (C300), and n-octadecane (PCM) were analyzed by fourier transform infrared (FTIR) spectroscopy for structural stability. The thermal conductivities of the various FGBs were analyzed by TCi thermal conductivity analyzer, and their hygroscopic properties were analyzed based on ISO 12,571 and 12,572. In addition, the hygrothermal performance of walls applied with FGB was evaluated using Wäme und Feuchte instationär (WUFI) simulation; the wall composition was concrete wall. As a result, the thermal conductivities of FGB were decreased by 15%, compared with the conventional gypsum board. In the case of moisture properties, the water vapor resistance and water content of FGB were increased, compared with the conventional gypsum board (SR). However, the simulation results showed that there were no moisture problems, such as condensation, mold growth, or structural damage.

Effects of alginate-glycerol-citric acid concentrations on selected physical, mechanical, and barrier properties of papaya puree-based edible films and coatings, as evaluated by response surface methodology

The development of edible coatings is an interesting strategy to reduce the use of conventional packaging materials and extend the shelf life of minimally processed fruits. The potential of papaya puree (PP) as a base for formulating edible films and coatings containing alginate (0.5–1.0 g/100 mL), glycerol (0.8–1.5 g/100 mL), and citric acid (0.5–1.0 g/100 mL) was evaluated. A Box–Behnken experimental design was used to determine the effect of independent variables on selected physical and mechanical properties, water vapor permeability (WVP) of PP edible films (PPEFs), and the surface solid density (SSD) and water vapor resistance of PP coating solutions (PPCSs) applied to papaya cubes. Furthermore, the PPEFs and PPCSs were optimized and validated using response surface models. Alginate-citric acid and glycerol-citric acid interactions significantly affected the SSD. The highest puncture strength of PPEFs was 17.94 MPa, with the highest concentration of alginate, whereas the WVP increased with higher concentrations of glycerol and citric acid. The optimum concentrations of alginate, glycerol, and citric acid for PPCSs and PPEFs were predicted to be 0.50, 1.32, and 0.59 g/100 mL, and 0.78, 0.80, and 0.50 g/100 mL, respectively. The mean average relative percent deviations between the experimental and predicted values were less than 10%.

Thermal comfort properties of plasma-treated warp-knitted spacer fabric for the shoe insole

Thermo-physiological comfort properties are crucial aspects of interlining material comfort for shoe insole which can be examined for permeability and conductivity. Air and water vapour permeability, conductivity and resistance of thermal are the main criteria for thermo-physiological comfort properties. Clothing comfort can be enhanced through special finishes including plasma which is one among the well known for surface modification. Oxygen and argon atmospheric plasma were used to analyse the comfort properties of polyester warp-knitted spacer fabric based on the fabric thickness and gas processing time. The outcomes exposed a notable influence in the comfort properties of polyester spacer fabrics after the atmospheric plasma processing time. The results too pointed out that the water vapour permeability and thermal resistance increased, although the air permeability and thermal conductivity decreased with the atmospheric plasma processing. When considering all the values of plasma-treated spacer fabrics, the 3 mm thickness of polyester spacer fabric proved to have better response and comfort properties than the 2 and 4 mm spacer fabrics. The findings show that final comfort properties of polyester warp-knitted spacer fabrics can be improved by using plasma treatments, and argon plasma treatment is the best method when compared to the oxygen plasma treatment.