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The Importance of Globally Accepted Test Methods and Standards
Published in Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović, Standard Methods for Thermal Comfort Assessment of Clothing, 2019
Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović
Traditional Lycra fibres allow high moisture transfer. The enhanced moisture management in hydrophilic laminates and microporous waterproof membranes, such as Gore-Tex®, resumed the path of increased material and functional clothing development and replaced the conventional PTFE membranes, which released the water vapour, however, not the droplets of sweat. Gore-Tex is a breathable waterproof fabric offering complete protection from water and wind, while simultaneously allowing body perspiration and heat release through a microporous membrane film laminated in between a lining and an outer shell textile. The X-BIONIC’s Symbionic Membrane®, inspired by amphibian skin, is capable of transferring both water vapour and droplets of sweat from the microclimate between the skin and the clothing, thereby reducing the risk of heat stress. The Polartec® Power Stretch® wind resistant, abrasion resistant and breathable material keeps the skin dry using touch points on the fabric’s inner surface to wick off the sweat to the outside of the fabric, where it spreads out to many times its original surface area, enabling it to dry at least two times faster than cotton (McCann and Bryson, 2009; Shishoo, 2015).
Packaging, Air Cleaning, and Storage of Humidity Sensors
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
Usually to protect against external influences and contaminants, the top of the package or the holes in the lid are made of wire mesh for air flow to the sensor. In addition to the wire mesh, a water-vapor-permeable filter is usually used to present contamination of the sensor. Although the diffusion of water vapor through some materials, such as some cellulose products, is theoretically more rapid than for still air, porous-hydrophobic membranes achieve better diffusion rates in practice. It was established that a material like Gore-Tex™ can be used as such a membrane. Gore-Tex is a waterproof, breathable fabric membrane and registered trademark of W. L. Gore and Associates. Invented in 1969, Gore-Tex is able to repel liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabric for all-weather use. It is composed of stretched polytetrafluoroethylene (PTFE), which is more commonly known as the generic trademark Teflon. Thus, the use of PTFE layer allows the water vapor through to the sensor, while preventing degradation performance due to appearance of particulates or oil (Dean et al. 2005). In particular, such an approach was used by Silicon Labs (www.silabs.com/humidity-sensor) for protection of the Si7005 Relative Humidity Sensor (see Figure 24.10a), by Hygrometrix Inc. (2000) (www.hygrometrix.net/) for protection of the HMX2000 RH sensor (Figure 24.10b), and by Sensirion (www.sensirion.com) for protection of humidity sensors in the SHTx series (Figure 24.10c). In last case, the PTFE-based membrane cover was attached to the sensor package by a double-faced adhesive tape. The developers claim that the cover has a minimal effect on the response time. The cavity inside the filter cap is designed so that the volume between membrane and sensor is negligible; hence, the impact on response time for humidity measurements is reduced to a minimum. The sensor can also be protected by sealing it in an envelope of a thin (less than 0.5 mm) silicone membrane. The envelope should not touch the sensor surface. As it was shown in the previous section, Versapor® film can also be used as a protective cover for humidity sensors (Courbat et al. 2010; Molina-Lopez et al. 2015). The Versapor film is an acrylic copolymer membrane. It is Repel™ treated for superior oleophobicity and hydrophobicity. Membranes have excellent air permeability, broad chemical compatibility, and good compatible with a variety of sealing methods.
Influence of nanotechnology in polymeric textiles, applications, and fight against COVID-19
Published in The Journal of The Textile Institute, 2021
Gore-Tex (GT) refers to a low-weight, water repelling, breathable textile membrane composed of enlarged polytetrafluoroethylene (ePTFE) applicable in electronics, medical devices, and fabrics (Gore, 1976). GT display a microporous architecture capable of being stretched about 800% of its initial configuration (Gore & Allen, 1980). Although GT technology emanated from microporous architectures, nanostructures have recently been included by the manufacturers (Coyle et al., 2010). Nano and NanoPro jackets have been fabricated along with Marmot LLC (“Marmot’s Nano AS Jacket”). Many other nanotechnology fabrics include Nyagraph (Nyacol NanoTechnologies, Inc.) burning protecting materials (Panse, 2013), PTFE functionalized nanoemulsions (Xu & Hegenbarth, 2014), nanofibrous prefiltration layerings (Gebert, 2014), and NPs for enhanced insulative electrical conductors (Cotter et al., 1996).
Heat, moisture and air transport through clothing textiles
Published in Textile Progress, 2020
The thermal protection of protective fabrics is influenced by fabric structure and properties such as air permeability and thickness. Air gaps and increases in the thickness of the fabric enhance its thermal protection as they obstruct the transfer of heat from the body. In order to provide protection against hot liquid, impermeable fabrics are used, however, such fabrics will obstruct the transfer of heat and water vapour from the body, so instead, semi-permeable membrane layers that are permeable to air but impermeable to liquid are incorporated into the fabric because they allow the passage of water vapour and heat transfer. Chen et al. (2018) suggested that the air permeability of the fabric must be less than 5 cm3/cm2 s in order to have fabrics that can provide protection against hot liquids. Membranes like Gore-Tex™ have pores large enough to allow single water molecules in water vapour to pass through but are too small for clusters of water molecules, such as those which exist when water is in the liquid state, to penetrate. This allows the Gore-Tex™ membranes to be used in liquid-proof, breathable fabrics which ensures fabric comfort (Huang & Qian, 2007).