Air Barrier Research Articles

Bio-inspired clay nanosheets/polymer matrix/mineral nanofibers ternary composite films with optimal balance of strength and toughness

Although remarkable progress has been witnessed in mimicking the nacre-like architecture in laboratory, it remains a great challenge for understanding the unique balancing mechanism of toughness and strength in biological materials. Here, taking advantage of the synergistic effect of different dimensional nanoscale building blocks, we fabricate nacre-like films that reconcile high strength and toughness. The obtained ternary lamellar composite films are constructed by one-dimensional xonotlite nanowires and two-dimensional montmorillonite nanosheets with the assistance of poly(vinyl alcohol). The ternary composite films show high strength ( (241.8±10.2) MPa) and toughness ((5.85±0.46) MJ m−3), both of which are higher than that of the single nanofibrillar xonotlite network films or the binary montmorillonite/poly(vinyl alcohol) composite films. The excellent mechanical properties of the nacre-like ternary composite films are aroused by the synergistic toughening mechanism of the different dimensional building blocks. This strategy provides a facile approach to integrate the nacre-like composite films with potential applications in tissue engineering scaffold, strong air barrier coatings, and fire-retardant packing materials.

Coatability of cellulose nanofibril suspensions: Role of rheology and water retention

Cellulose nanofibril (CNF) suspensions are not easily coatable because of their excessively high viscosity and yield stress, even at low solids concentrations. In addition, CNF suspensions vary widely in their properties depending on the production process used, which can affect their processability. This work reports roll-to-roll coating of three different types of CNF suspensions with a slot-die, and the influence of rheology and water retention on coatability is addressed. The impact of CMC addition on the high and low shear rate rheology, water retention, coatability, and final coating quality of these suspensions is reported. All three CNF suspensions were coated successfully using the slot-die coating process. CMC addition further improved the coatability by positively influencing both the low and high shear rate viscosity and water retention of the CNF suspensions. All CNF coatings significantly improved the air, heptane vapor, grease and oil barrier, while reducing the water vapor transmission rate to some extent.

B-34 ガラス窓の日射遮蔽物による熱特性に関する研究 (第2報) プッシュプル型エアバリア方式の排熱特性

B-34 ガラス窓の日射遮蔽物による熱特性に関する研究 (第2報) プッシュプル型エアバリア方式の排熱特性

A comparative study of the effect of clay and titanium dioxide on the mechanical properties and permeability of nanocoated cotton fabrics

ABSTRACTThis paper explores a comparison of mechanical properties of nanocoated cotton fabric for coatings synthesized with two different additives: Tunisian natural clay and titanium dioxide. The natural raw clay is a mixture of various other simple clays (kaolinite, calcite, illite, and quartz) requires preparation. TiO2 and Tunisian clay were added to two different resins, polyacrylate and polyurethane, widely used for numerous textile improvements such as impermeability and brightness effects. The additives used offer the advantage of being nontoxic and widely available. First, we check the constitution of the nanocoatings via X‐ray diffraction. Then, a defined amount of the resulting solution is applied on a cotton fabric. Finally, we check the mechanical properties and barrier effects on the modified fabric. The results show that when a small amount of clay or TiO2 particles are added to resin, the tear, tensile, bursting, and abrasion strength and water and air barrier properties of the coated fabric are globally enhanced. However, the use of natural clay in the coating gives better results than TiO2. In fact, in terms of mechanical performance, it is two to nine times more efficient than the titanium dioxide coating, except for the barrier effect, which is exactly two times more efficient. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45642.

Experimental assessment of rainwater management of a ventilated façade

Façades are not watertight systems in which the exterior surface of the cladding plays the role of the water shedding surface; the air space is the drainage plane; the exterior surface of the thermal insulation layer acts as water-resistive barrier, and the interior layer of the inner leaf is supposed to be the air barrier. The degree of watertightness of ventilated façades relies on the characteristics of the materials used, the geometry of the external cladding element, and edge profile of the joints. Hence, in this article, we extrapolate the laboratory testing to develop a holistic approach on the water management of ventilated façades. The laboratory test showed that 50% of the water deposited to the surface of the wall splashes back, 22% creates a runoff film along the exterior surface of the cladding, 27% infiltrates into the cavity behind the cladding, and <1% reaches the inner layer of the wall. Given these results, the moisture load has been determined for a range of wind-driven rain loads and vertical joint configurations. Such information can be used as input to hygrothermal simulations.

Comparison of computed tomography shielding design methods using RadShield

Purpose. To comprehensively compare four computed tomography (CT) scanner shielding design methods using RadShield, a Java-based graphical user interface (GUI). Methods. RadShield, a floor plan based GUI, was extended to calculate air kerma and barrier thickness using accepted methods from the National Council on Radiation Protection and Measurements (NCRP), the British Institute of Radiology, and a method using isodose maps, for spatially distributed points beyond user defined barriers. For a stationary CT scanner, the overall shielding recommendations found using RadShield were also compared to those found by American Board of Radiology certified diagnostic medical physicists using the conventional NCRP dose length product method and the isodose map method. Results. The results between methods differed significantly for calculation point locations beyond the gantry and to the rear of the gantry. Overall shielding design recommendations across the four methods yielded similar average air kerma and thickness values for the barriers. Conclusions. RadShield was extended to perform CT shielding design and proved reliable using four methods.

Experimental air curtain solution for refuge alternatives in underground mines

To provide an optimal aerodynamic sealing solution for an alternative refuge in underground mine, a commercial air knife was selected as the air curtain device (ACD) for its lower compressed air use and uniform airflow. A series of simulated chamber model experiments were then performed to evaluate the sealing efficiency of different ACD configurations and the influence of interruption by transiting personnel on ACD performance. By considering the overall sealing efficiency, stability and air consumption, a double-sided ACD equipped with a baffle on the side exposed to harmful gases inside the entrance of the protected door is proposed as the most suitable configuration. This requires compressed air to be supplied at a pressure of 0.10–0.20MPa to generate an air barrier, which means that a standard compressed air cylinder (40L, 15MPa) can provide suitable sealing conditions for a period of about 3.5min.

Influence of ethanol vapor addition on the surface modification of polyethylene in a dielectric barrier discharge

In this paper, ethanol vapor up to 50% is added to an argon, air or nitrogen dielectric barrier discharge at medium pressure to profoundly investigate the effect of ethanol addition on the surface modification of low density polyethylene (LDPE). Water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS) measurements show that the ethanol vapor addition effect on the LDPE surface depends on the used carrier gas. Adding ethanol to an argon plasma has no significant effect on the wettability nor on the chemical composition of LDPE compared to a pure argon plasma treatment. Ethanol addition does however slightly increase the LDPE surface roughness. Addition of small amounts of ethanol vapor to an air plasma makes it possible to incorporate additional nitrogen and oxygen groups on the LDPE surface, resulting in an extra decrease of 11% in WCA value. Moreover, the LDPE surface roughness is slightly increased due to the ethanol vapor addition. The most significant effect of ethanol addition is however observed when nitrogen is used as carrier gas. After an N2/2% ethanol plasma treatment, an 85% reduction in WCA value to 8.5° is found compared to a pure N2 plasma treatment. This very hydrophilic LDPE surface is obtained due to a significantly high incorporation of oxygen and nitrogen groups on the surface with an O/C and N/C ratio reaching 32% and 53% respectively. FTIR measurements also reveal that the observed extremely high wettability of LDPE is not the result of plasma activation but is due to plasma polymerization effects occurring on the surface resulting into the deposition of a plasma polymer containing ketones, amides as well as CN groups. In addition, ageing studies have also been conducted and these studies reveal that for all carrier gases, ethanol addition to the discharge gas significantly suppresses the ageing effect. All the above mentioned conclusions therefore indicate that ethanol vapor based plasmas can be an excellent tool to increase the surface energy of polymers.

Cellulose nanofiber/carboxymethyl cellulose blends as an efficient coating to improve the structure and barrier properties of paperboard

Cellulose nanofibers (CNF) have been suggested in the literature as a potential barrier coating layer for paper and paperboard. However, due to its rheological properties and solids content, the material is difficult to apply to paper at significant coat weight levels. The use of CNF as a coating to improve the structure and barrier properties of paperboard was investigated. Two forms of CNF were used: (1) refiner produced material and (2) material produced with an ultra-fine grinder. Carboxymethyl cellulose (CMC) was used for some samples as an additive. The rheology of these suspensions was characterized. These materials were applied onto the surface of paperboard using a draw-down rod coater in two layers. Scanning electron microscope (SEM) was used to see the coverage of the paper by the CNF layer. Air permeability, water penetration and barrier properties of the samples were characterized. The steady shear viscosity of CNF suspension decreased after the addition of CMC. Although CNF at 2% solid content without CMC could not be spread out onto the surface of paper uniformly, 3% CNF along with CMC was successfully coated on the surface of paper: CMC acts as a dispersant that produces a uniform suspension with minimal flocs. The ground CNF with CMC produced the best samples with good coverage as revealed by SEM images. The results show that the structure and barrier properties of coated paperboards improved considerably by the application of CNF coatings.

Synthesis of hybrid paper sheets with enhanced air barrier and antimicrobial properties for food packaging

Paper sheets made from bagasse pulp have been modified using nanocellulose (NC) obtained from the same raw material. Modification of paper sheets have been carried out either through loading of paper with different concentrations of NC and antibacterial agent, Chitosan (Ch) during making sheets, or by surface coating of the paper. Crystals of NC extracted using concentrated sulfuric acid from bagasse pulp were found to have crystallinity index (CrI) 90%. Morphology of obtained NC has been confirmed by TEM and images revealed formation of NC crystals with large size distribution ranges from 4 to 60nm. Mechanical properties and air permeability of paper sheets loaded with different ratios of NC and Ch have been investigated. The results showed that presence of NC did not negatively affect the obtained modified paper sheets, while air permeability decreased with adding 8% NC to paper matrix. On the other hand, surface coverage of paper sheets with NC greatly reduced air permeability. Antimicrobial investigations carried out by optical density method indicated that presence of Ch in the paper sheets as an additive or in a coating formulation enhanced paper resistance to different microorganisms especially those causing food poisoning. The current study confirms that the modified paper can have potential application in food packaging.

Air barrier effect in out of mesh jet lubrication of ultra-high speed spur gears

PurposeThis paper aims to reveal the mechanism of air barrier effect in jet lubrication and to figure out the influence of gear parameters and conditions on air barrier, thus providing guidance to the design of jet lubrication in ultra-high speed gear cooling system.Design/methodology/approachThe computational fluid dynamics method is used to calculate the flow and pressure of ultra-high speed gears. The flow and pressure distributions are obtained under different gear parameters and working conditions, so their variations are obtained. A multiphase flow model is established to simulate the flow regime of oil jet to ultra-high speed gears. Simple experiments are carried out to observe the air barrier effect of high-speed gears.FindingsAir barrier effect exists in the jet lubrication of ultra-high speed spur gears, which could prevent oil jet to reach on the gear surfaces. The results show that the generated pressure has positive relations with gear speed, module and width; however, as the increasing of gear width, their marginal contribution to pressure is decreasing. The computational results coincide well with the experimental results.Originality/valueThe research presented here proposed the air barrier effect of ultra-high speed gears for the first time. It also leads to a design reference guideline that could be used in jet lubrication of ultra-high speed gears, thus preventing lubrication and cooling failures.

Plant Growth Enhancement of Seeds Immersed in Plasma Activated Water

ABSTRACTWe have produced plasma activated water (PAW) using air, O2, N2, He and Ar atmospheric pressure dielectric barrier discharge plasma irradiation to deionized water. Then, PAW was kept for 1 hour or 1 day at room temperature to reduce concentrations of short lifetime reactive oxygen species and reactive nitrogen species before supplying to plants. O2, air and N2PAW induces growth enhancement of plants. For 1 hour PAW supply the longest seedling length after 3 days cultivation is 1.62, 1.38, 1.13, 1.12, and 1.04 times long for air, O2, He, N2, and Ar plasmas compared with the length for thecontrol, whereas for 1 day PAW supply it is 1.52, 1.28, 1.13, 1.10, and 1.08 times long for air, O2, He, N2and Ar. Therefore, long lifetime reactive oxygen nitrogen species in PAW is effective for the growth enhancement.

Improvement of Lubrication and Cooling in Grinding by Effective Controlling of Air Boundary

The presence of air around a rotating grinding wheel impedes the effective entry of coolant into grinding zone. Therefore, a proficient method is required to minimize this air boundary before the impingement of fluid-jet into the grinding zone. This paper is an experimental study for finding the better effective method of controlling the air boundary around the wheel. Further, two different techniques of suppressing the air barrier has been studied experimentally and statistically towards improving the cutting fluid action in grinding. Fuzzy models are developed to interpret the relationship between the variables and responses. Experiments are conducted on a horizontal surface grinding machine with the application of scraper board and pneumatic barrier separately behind the flood cooling nozzle. The surface roughness and other mechanical properties of these two methods and traditional flood cooling method are compared. The experimental results specified that the tangential force and the requirement of specific energy are reduced by maximum 25% and 20% respectively by the scraper board (SB) with the comparison to the pneumatic barrier (PnB) method for achieving the equivalent surface quality when tested by positioning them at 60° location from grinding zone. Hence, use of scraper board at close proximity to grinding zone is recommended.

Cellulose nanocrystals as new bio-based coating layer for improving fiber-based mechanical and barrier properties

In this work, we explored the elaboration of new smart paper by coating fiber-based materials with CNC for possible use in packaging. Particularly, we investigated application of a 100% CNC layer onto a substrate. Mainly due to the cost and limited availability of CNC on a large scale, few studies have examined these opportunities. Several layers of CNC were deposited onto a paper material using the bar-coating process to improve relevant properties of the paper surface. Surface analyses (atomic force microscopy, scanning electron microscopy, and transmission electron microscopy) were performed to elucidate the CNC network at the paper surface. Structural and mechanical properties of the final materials were evaluated. Results of general interest were obtained about barrier properties. The air barrier and grease resistance improve only with the paper coated with CNC. To complete this research, a small amount of polyethylene glycol was added to reinforce the brittle CNC coating and clearly enhance barrier properties of the paper.

Durability of self-adhesive tapes for exterior air barrier applications: a laboratory investigation

ABSTRACTIn timber frame construction in Europe, air barrier systems are typically realised at the interior side of the building envelope. Yet, in some applications such as renovation projects, it can be easier to provide the air barrier layer at the exterior. An exterior air barrier system, typically board materials in which the joints are sealed with tape, needs to withstand severe outdoor weather conditions and maintain pre-defined air permeability values. The aim of the present article is to investigate the impact of severe climatic conditions on the airtightness of typical taped joints. The airtightness of 32 wood fibre cement board samples has been investigated. Each specimen has a 2 mm wide joint. Two different kinds of commercially available tapes were used to seal these joints. Airtightness of all specimens has been tested before and after accelerated ageing procedures that mimic real exterior climate conditions. Three different ageing protocols were selected: (1) temperature cycles, (2) temperature, rain and frost cycles and (3) UV exposure alternate with high humid conditions. The present paper discusses the durability of the two tapes by comparing the air permeability of the specimens before and after accelerated ageing exposure. The results indicate that for both tapes tested the impact of the three artificial ageing methods on the air permeability is limited (increment less than 2 × 10−5 m3/m/h/Pa).

STUDY ON THE PROTECTION OF ISOLATED RABBIT'S PULMONARY ISCHEMIA REPERFUSION INJURY BY ADDING TANSHINONE IIA INTO LOW POTASSIUM DEXTRAN SOLUTION

Purpose: This study investigates the protective effect of Tanshinone IIA (Tan IIA) on isolated rabbit's pulmonary ischemia reperfusion injury (IRI) and discusses its potential for the treatment of microcirculation disorders. Methods: We chose isolated rabbit's IRI as our experimental models, and randomly divided 24 New Zealand rabbits into two groups. For the control group (L), the lungs were perfused with Low Potassium Dextran (LPD) solution under 4[Formula: see text]C, and then it was preserved under 10[Formula: see text]C. For the experimental group (LT), the lungs were perfused and preserved with LPD[Formula: see text]Tan solution using the same approach. After the lungs have been preserved for 18[Formula: see text]h, we again perfused it for another 30 min. After reperfusion was completed, we determined the contents of SOD, NO, and MDA immediately. The wet to dry weight ratio (W/[Formula: see text] was then obtained. Finally, we use a combination of light microscopy and transmission electron microscopy to observe the ultra-structural changes of lung tissues. Results: We discovered that the contents of SOD and NO in group LT were higher than that in group L ([Formula: see text]). However, the MDA and the W/D values in group LT were lower than that in group L ([Formula: see text] or [Formula: see text]). We also observed that part of the tissues has hyperemia, edema, and congestion. Under the light microscopy, the structures of the pulmonary alveoli, bronchi, and capillaries were complete. But under high-power field, group L had a more obvious phenomenon of alveolar epithelium and capillary epithelium cells swelling and hypertrophy with respect to group LT. It could be observed that in the partial tissues, erythrocytes exuded from alveoli and the interval tends to widen in the alveoli. Under transmission electron microscopy, group L is observed to have mitochondria swelling, vacuolization, and even autosome edge accumulation. Microvillus of cell Type II significantly decreased or disappeared. Blood–air barrier swelled severely and a portion of it was cracked. The phenomena above were obviously reduced for group LT. Conclusion: Our experiments confirmed that adding Tan IIA into LPD solution can reduce the isolated rabbit's IRI effectively.

Association of Airborne Microorganisms in the Operating Room With Implant Infections: A Randomized Controlled Trial.

clinicaltrials.gov Identifier: NCT01610271 Infect Control Hosp Epidemiol 2016;1-8.

Influence of Moisture Dry-out on Hygrothermal Performance of Prefabricated Modular Renovation Elements

Renovation with prefabricated modular panels is one way to achieve high energy efficiency and quality both in production and installation processes. The 5-storey building, which is being fully renovated in Tallinn, Estonia, will be insulated with prefabricated modular renovation elements. The hygrothermal performance of the envelope was evaluated with calibrated dynamic hygrothermal simulations and with a mould index model, where calculation results were in good agreement with measured data and are therefore reliable for further research. The calculations were made to evaluate the hygrothermal risks in the building envelope and after the prefabricated modular elements were installed. The focus was on studying concrete wall's dry-out capability and the use of vapor barrier. The initial moisture content of the concrete wall and a right choice of air&vapor barrier layer has considerable impact on the entire envelope performance. As a result of this study, we claim that the risk of mould growth in this structure can be minimized, when the initial moisture content (IMC) of the existing concrete large panel element is w≤55 kg/m3 and PE-foil as air&vapor barrier is used or when IMC is w≤75 kg/m3 and the oriented strand board (OSB) as vapor control layer or when IMC is w≤110 kg/m3 and smart vapor retarder (0.2 m<Sd <5 m) on the mounted modular element as vapor control layer is used, in combination with the prefabricated modular element's insulation, with high thermal resistance and vapor permeability (thermal resistance R≥7.5 m2·K/W; equivalent air layer thickness Sd≤0.5 m), and wind barrier (R≥0.8 m2·K/W; Sd≤0.05 m) layers. In the renovation of prefabricated concrete large panel buildings, it is possible to achieve good results and build sustainable solutions according to up-to-date requirements of nZEB in a cold and humid climate.

On interior rehabilitation of buildings with historic facades

The first part of this overview deals with an effect of interior insulation that changes thermal regime in a wall and thereby affects moisture performance of this wall. Moderately cold and wet climate is probably the most difficult to deal with because any interior insulation increases a number of freeze-thaw cycles that takes place during winters. In this respect, materials used for interior thermal insulation are separated depending on their air leakage characteristics and where needed an additional air barrier system is added. This article discusses one-step freeze-thaw method for assessment of clay brick durability and different materials that can be used for interior insulation.

Investigation of the proposed solar-driven moisture phenomenon in asphalt shingle roofs

Unvented attics are an energy-efficiency measure to reduce the thermal load of the conditioned space and decrease the space conditioning energy consumption by about 10%. This retrofit is usually done by spraying polyurethane foam underneath the roof sheathing, and on the gables and soffits of an attic to provide an air barrier and a thermal control layer. Unvented attics perform well from this perspective, but from a moisture perspective sometimes homes with unvented attics have high interior humidity or moisture damage to the roof. As homes become more air tight and energy efficient, a better understanding of the hygrothermal dynamics of homes with energy-efficient envelopes becomes more important. One proposed reason for high unvented attic humidity has been that moisture can come through the asphalt shingle roof system and increase the moisture content of the roof sheathing and attic air. This has been called “solar-driven moisture.” Oak Ridge National Laboratory investigated this proposed phenomenon by examining the physical properties of a roof and the physics required for the phenomenon. Results showed that there are not favorable conditions for solar-driven moisture to occur. Oak Ridge National Laboratory also conducted an experimental study in a home with an unvented attic and compared the humidity below the roof sheathing before and after a vapor impermeable underlayment was installed. There was no statistically significant difference in absolute humidity before and after the impermeable underlayment was installed. The outcomes of the theoretical and experimental studies suggest that solar-driven moisture does not occur in any significant amount.