Thermodynamics of aerogel-treated nonwoven fabrics at subzero temperatures

Polymers for Advanced Techs

Militký

et al. 2018

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The primary purpose of cold weather clothing is to shield the wearer from the extremities of the external environment. The thermal properties of nanofibers and their potential applications have tremendous scope and application in this area. The objective of this study was to investigate the mechanisms of heat transfer through fibrous insulation where the fiber diameter was less than 1 μm. Electrospinning process was used to produce flexible polyurethane and polyvinylidene fluoride nanofibers embedded with silica aerogel. The thermal and transport behavior of the samples was evaluated, and results were statistically analyzed. Presence of aerogel particles were confirmed through microscopic examination. Thermal behavior was investigated by using thermogravimetric analysis and differential scanning calorimetry. The results showed that the polyvinylidene fluoride nanofibrous membranes embedded with aerogel obtained a good thermal stability with lower weight loss than polyurethane nanofibrous membranes. The glass transition and melting point was not affected by the aerogel content in the layers, validating that polymers are not miscible. The increase in duration of electrospinning led to higher web thickness, which resulted in considerable decrease in air permeability. Considerable improvement of thermal insulation was observed by increasing the number and the weight per unit area of both nanofibrous membranes. The results confirmed increase in thermal insulation by embedding silica aerogel in nanofibrous membranes. With reference to the results, it could be concluded that nanofibers embedded with aerogel are good for thermal insulation in cold weather conditions. Thermal insulation battings incorporating nanofibers could possibly decrease the weight and bulk of current thermal protective clothing.

Section: Resultsmentioning

confidence: 99%

Electrospun nanofibrous membranes embedded with aerogel for advanced thermal and transport properties

Polymers for Advanced Techs

Militký

et al. 2018

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“…This difference can be explained by the presence of aerogel in the sample (Venkataraman, Mishra, Jasikova, Kotresh, & Militky, 2014) and the dense threedimensional lattice of the micro-and nano air pores inside their structure. It should be noticed that the aerogel present between fibers and the overall thickness of the material can dramatically influence heat exchanges Venkataraman, Mishra, & Wiener et al, 2014).…”

Section: Thermal Conductivity Analysismentioning

confidence: 94%

Effect of compressibility on heat transport phenomena in aerogel-treated nonwoven fabrics

The Journal of The Textile Institute

Kotresh

et al. 2015

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The heat transport properties observed in nanostructured materials such as aerogel-treated nonwoven fabrics are promoting revolutionary breakthroughs as thermal insulators. This article is focused on the thermal transport characteristics of nonwoven fabrics treated with aerogel for potential uses in thermal protective applications. Highly efficient aerogel thermal blankets are now considered a viable option in applications such as clothing, building, and pipelines. A variety of fiber and fabric structures or finishing parameters influence the functional properties of nonwoven materials. In order to assess the thermal properties of aerogel-treated nonwoven fabrics, the KES Thermolabo II and NT-H1 (plate/fabric/plate method for thermal conductivity, q max cool/warm feeling, and thermal insulation) was used. Fabrics of higher thicknesses show lower heat conductance and therefore higher thermal insulation properties. It has been found that thermal insulation is also related to the weight and compressional properties of the fabric. To make an insulating material effective, it should have low compression set and high resiliency to make the still air to be entrapped into the fibrous material.

“…It is best suited for thermal insulation applications. Due to high volume of porosity (>95%) and pore sizes, aerogel has high thermal insulation properties (Venkataraman, Mishra, Jasikova, Kotresh, & Militky, 2014). Silica aerogel primarily consists of air which leads to a low solid thermal conductivity (Fricke, Lu, Wang, Buttner, & Heineman, 1992).…”

Section: Novel Techniques To Analyse Thermal Performance Of Aerogel-tmentioning

confidence: 98%

Novel techniques to analyse thermal performance of aerogel-treated blankets under extreme temperatures

The Journal of The Textile Institute

Wiener

et al. 2014

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The thermal properties of polyester/polyethylene non-woven blankets of varying thicknesses impregnated with aerogel were studied and compared. The SEM images were also taken to study the physical configuration of the aerogel-based fibrous webs. Specific thermal properties like conductivity, resistance and effusivity were measured using C-Therm TCi thermal conductivity analyzer. One major objective was to understand the potential of a newly fabricated equipment to study the thermal properties of non-woven textile fabrics treated with aerogel at sub-zero temperatures. Thermal conductivity was calculated using the empirical relation in Fourier's law. The relationship between the thermal conductivity and thermal resistance of the samples was studied at various environmental temperatures (which was set in the climatic temperature system between (+25°C and −25°C). The newly fabricated equipment was found to be suitable for thermal measurements at sub-zero temperatures. The results were statistically analysed and compared. It was found that fabric thickness and density have a significant effect on the thermal properties and permeability of the aerogeltreated non-woven fabrics. The results also showed that the selected polyester and polyethylene non-woven fabrics were suitable for usage as thermal insulators during construction of buildings and for insulation of oil and gas pipelines.