Water Vapor Permeability Characteristics Research Articles

Investigation of the relation between free volume and physico-mechanical performance in rigid polyurethane foam containing turkey feather fibers: Part 2

Rigid polyurethane foams (RPUFs) were modified with 0–15 wt.% turkey feather fibers (TFFs) produced from waste turkey feathers. One-shut free rising method was used for the production of TFFs-filled-RPUFs in a closed mold. The dependence of mechanical performance and water vapor permeability (WVP) feature of the final foams on TFFs loading was evaluated with free volume change. The free volume analysis was performed via Positron Annihilation Lifetime Spectroscopy (PALS), while the mechanical and WVP characteristics were determined with the use of the universal tester machines. PALS findings showed that the incorporation of TFFs with RPUF matrix caused the considerable diminishment in the free volume due to TFFs serving as a filling material and formation of strong secondary bonds between components. Moreover, tensile strength and extension of the foams decreased with the increasing of TFFs, which caused by the occurrence of noteworthy restriction on the spatial alignment and orientation capability of polyurethane chains due to the lack of sufficient free volume allowing the chains to move freely. As for the compression tests, all the TFFs-loaded RPUFs depicted substantially lower performance due to TFFs interfering with the ordered organization of isocyanate domains. Moreover, impact test results showed that the addition of TFFs into RPUF matrix brought about the insufficient impact energy delocalization throughout the matrix due to the restriction on the mobility of polymer chains. Additionally, the remarkable diminishment in WVP was recorded due to the reduction in the number of vacancies and constitution of keratin composed of roundly 60% of hydrophilic protein (especially cystine). All in all, this study established a strong links between free volume and characteristics of TFFs-loaded RPUFs.

Influence of the Water Vapour Permeability of Airtight Sheets on the Behaviour of Facade

The air-tightness of the thermal envelope of buildings is one of the measures to reduce their energy demands in order to achieve global warming reduction targets. To this end, airtight sheets with different water vapour permeability characteristics are used. The different products studied are highly dispersed in terms of equivalent air thickness values, leading to confusion. After the analysis carried out, it is concluded that all airtight sheets are vapour barriers. To clarify whether or not these sheets are necessary as vapour barriers, a condensation analysis was carried out on 13 different facades for 3 climate zones with severe winters as defined in Spanish regulations. The results reveal that interstitial condensation occurs in only 7 of the 39 case studies, with the traditional facades of brickwork with render causing the greatest problems if the appropriate products are not used. In these cases, airtight sheets with water vapour barrier characteristics must be applied on the interior face of the insulating material. In all other cases (32), the airtight sheets must be permeable to water vapour if it is looked for a more breathable wall to water vapour and a better control of the interior humidity conditions.

Thermal comfort properties of weft knitted quilted fabrics

PurposeThis paper investigates the thermal comfort properties of quilted (jersey cord) fabrics produced with different width of diamond pattern, different filling yarn linear density and different types of material.Design/methodology/approachA total of 12 fabrics were knitted by varying the width of diamond pattern (1 and 3 cm), the filling yarn linear density (300 and 900 denier) and the type of materials (cotton, polyester and their combination). In this regard, air permeability, thermal conductivity, thermal resistance, thermal absorptivity and relative water vapor permeability of these fabrics were measured and evaluated statistically.FindingsThe results showed that fabrics knitted using cotton yarn in both front and back surfaces exhibit higher thermal conductivity, thermal absorptivity and relative water vapor permeability characteristics; whereas samples knitted using polyester yarn in both surfaces have higher air permeability and thermal resistance. As the linear density of filling yarn increases, thickness and thermal resistance of the samples increase and air permeability, thermal conductivity, water vapor permeability characteristics decrease. When the effect of the width of diamond pattern compared, it is seen that an increase in the width of pattern lead to an increase in thickness and thermal resistance and a decrease in thermal conductivity, thermal absorptivity and water vapor permeability values.Originality/valueMany researches were carried out on the thermal comfort properties of knitted fabrics, however there is a lack of research efforts regarding thermal comfort properties of quilted fabrics.

Fluid flow in complex porous media: Experimental data and IFU model predictions for water vapour permeability

In this research work, an Intermingled Fractal Units' model (IFU's model) has been proposed with the aim of predicting water vapour permeability characteristics of porous rock, normally studied in gas reservoir field. IFU modelling approach commences with the reproduction of experimental pore size distribution with the help of diverse fractal base units mixed together. This procedure allows simulating the porous microstructure in terms of pore cumulative curve or pore size distribution. An analytical procedure is used for obtaining the permeability values. The studied rocks include limestone from South Sardinia quarries and have similar characteristics of those studied in gas reservoir field. They have been taken from four different parts (systems A, B, C and D) of the quarry for the assessment of the heterogeneity of this rock. From the experimental tests, the average water vapour permeability values are equal to 7.22 ± 1.22, 4.21 ± 1.51, 10.09 ± 1.11 and 10.12 ± 2.4210−12 kg m−1 s−1 Pa−1 respectively for systems A, B, C and D, whereas predictions by IFU are respectively equal to 7.15 ± 1.55, 4.25 ± 1.45, 10.12 ± 1.22 and 9.98 ± 2.1810−12 kg m−1 s−1 Pa−1. The comparison shows a good capacity of IFU procedure to predict water vapour permeability values.

Electrical evaluation of crack generation in SiNx and SiOxNy thin-film encapsulation layers for OLED displays

By measuring leakage current density, we detected crack generation in silicon nitride (SiNx) and silicon oxynitride (SiOxNy) thin-film encapsulation layers, and correlated with the films’ water vapor permeability characteristics. After repeated bending cycles, both the changes in water vapor transmission rate and leakage current density were directly proportional to the crack density. Thick SiNx films had better water vapor barrier characteristics in their pristine state, but cyclic loading led to fast failure. Varying the atomic concentration of the SiOxNy films affected their bending reliability. We attribute these differences to changes in the shape of the crack tip as the oxygen content varies.

Thermal Transmission Attributes of Knitted Structures Produced by Using Engineered Yarns

Thermal comfort has become an important parameter for clothing design. Factors affecting the thermal behavior of clothing are numerous and they include thermal insulation, transfer of moisture and vapor through clothing and heat exchange, etc. The aim of this study is to investigate the thermal comfort characteristics of knitted structures produced by using two different engineered yarns with the constructions of single jersey and pique. The air permeability, thermal resistance, thermal absorptivity, and water vapor permeability characteristics were tested. Besides the evaluation of the effects of yarn type and fabric construction, the fabrics were also categorized as dyed and undyed in order to analyze the effect of dyeing on the characteristics of fabrics. The results revealed that air permeability and thermal resistance values decreased after the dyeing process, while thermal absorptivity values increased. Pique fabric construction and fabrics produced with 100% engineered polyester yarn exhibit higher air permeability, higher thermal resistance, and lower thermal absorptivity attributes.

A new dynamic sweating hotplate system for steady-state and dynamic thermal comfort measurements

This paper discusses design details and measurement principles of a dynamic sweating hotplate system used for both steady-state thermal and water vapor resistance and dynamic water vapor transmission rate measurements. Dynamic and steady-state transfer measurements were carried out by separate systems in preceding studies. Water vapor resistance and dynamic water vapor transmission rate values were determined according to the new principles put forward in this study. Relationships between properties obtained by the new system and standard permeability (water vapor and air) parameters were determined for different types of fabrics used for sports clothing. The materials and physical/constructional properties of the investigated fabrics varied in a wide range as the aim was to determine if the developed system could differentiate their comfort performances. According to the results, water vapor resistance is significantly correlated with fabric weight and water vapor resistance is the best in differentiating the water vapor permeability characteristics of the fabrics among other transfer properties.

Performance Characteristics of Waterproof Breathable Fabrics

The effect of atmospheric conditions on the water vapour permeability characteristics of waterproof breathable fabrics has been studied. Several types of waterproof breathable fabrics were tested for vapour permeability under a wide range of atmospheric temperatures and relative humidities. It was found that atmospheric conditions have a considerable effect on the vapour permeability characteristics and that there are differences in behaviour between the various types of fabric. The two main variables influencing vapour permeability are identified. Regression equations for the relationship between vapour permeability and the main atmospheric parameter are presented. Conclusions are drawn about the capabilities of the fabrics under conditions of use.