Breathability: An Important Feature for Waterproof Apparel

Breathability: An Important Feature for Waterproof Apparel

Diksha Bisht , Mona Verma^* , Saroj Jeet Singh , Shalini Rukhaya

Department of Textile and Apparel Designing, CCS Haryana Agricultural University, Hisar, Haryana

Corresponding Author Email: monaverma35057@gmail.com

DOI : http://dx.doi.org/10.53709/CHE.2021.v02i04.032

Abstract

Keywords

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1. Introduction

There is a growing need for multifunctional apparel among consumers, particularly those who are often active in outdoor activities like sports or subjected to harsh weather conditions such as heat, snow, rain, cold and wind [27]. This is demonstrated by the worldwide waterproof breathable textiles market being valued at USD 1.7 billion in 2019 and is anticipated to grow at a revenue-based CAGR of 5.7 percent between 2020 and 2027. Due to the rising per capita income and colossal population, Asia Pacific emerged as the largest market for waterproof breathable textiles in 2019, accounting for 39.4 percent of global sales [49]. 

The best waterproof breathable fabrics based apparels are very comfortable to wear as they keep the wearers dry during hot or cold weather or windy or rainy conditions. Body heat is effectively dissipated by their high water vapour and air permeability, which helps maintain the optimum body temperature [25]. Furthermore, such garments should have high heat insulation characteristics, good handle, and lightweight, with the water vapour permeability of fabric being determined by both fabric’s thermal resistance and water vapour diffusion [56]. The difference in partial water vapour pressure between the two regions is the major driving factor for moisture to go from the body to the outside [6].

The body cools itself partly through sweat, which must evaporate and absorb energy (heat) in the process, resulting in cooling during physical and other activities and under specific situations. An athlete’s clothes, for example, must transfer 1.5 to 2.5 litres of moisture each hour during intense exercise [3]. Most of the stored energy is converted to heat instead of physical activity as human body is a relatively inefficient converter. Heat must be evacuated from the body via conduction, radiation and convection from the skin, as well as by evaporation of water generated by sweat glands for the body to maintain its 37°C core temperature. The first three are suitable for moderate activity levels, whilst the fourth is more suitable for high activity levels [21]. Such clothing must transport moisture away from the site where it is created i.e. skin, so that it does not stay on the skin or condense inside it. An important necessity for maintaining a comfortable temperature and a safe working environment is regulating air temperature and humidity, particularly in very hot or high activity environments or varied levels or combinations of these variables. As a result, there is a rise in the relative humidity of the microclimate inside clothing, which leads to increased heat conductivity and uncomfortable clothing [57]. 

The skin temperature ranges between 33ᵒC and 35ᵒC depending on the circumstances, but the typical core body temperature is 37ᵒC. The core body temperature must be between 24 and 45 degrees Celsius for a human to survive. Hypothermia can occur in extreme situations when the body loses heat faster than it can create it, for eg. when physical activity has ceased, resulting in a drop in core temperature. When perspiration does not evaporate and liquid sweat is created, the body cannot cool at the same rate as heat is generated, such as during physical exercise. Hyperthermia, can develop when the body core temperature rises [22]. 

Figure 1 (a) Waterproof fabric, (b) Waterproof breathable fabric

All across history, wearing many layers or various clothes tailored with a specific function has been the norm. For example, a thick coat might be worn over clothing to protect against cold, and if waterproof, also against rain as Macintosh was worn over clothing when just rain protection was necessary. As early as 1823 Charles Macintosh developed one of the first raincoats, coating a cloth with rudimentary rubber. These clothes did not let sweat and water vapour escape, causing the user to get dehydrated [46]. Since most traditional clothes are breathable, but not waterproof, the topic of breathability only arises when the garment is anticipated to fulfill protective qualities, especially rain protection. A fabric layer contacting the skin should drain liquid sweat away from the skin as fast as possible, without becoming or feeling damp [5]. When designing such fabrics and garments, the biggest challenge is to ensure that air, water vapour and perspiration may readily flow from the inside of a fabric to the outside, while creating a barrier against liquid water (opposed to water vapour) entering from outside. This is a conflicting case, hence there must be a compromise. Also, a multifunctional finish or feature applied to a fabric should not adversely influence the fabric’s handling and comfort qualities [32].

Figure 2 Structure of waterproof breathable fabric

Breathability and waterproofness are completely separate concepts, but they are often mixed in the word ‘breathability’ in the modern world. If the fabric is breathable, it will allow water vapour (molecular diameter less than 0.04 microns) to flow through and inhibit the entrance of water (molecular diameter greater than 0.100 microns) [37]. The moisture vapour transmission rate (MVTR) is used to calculate the value of breathability by measuring the amount of moisture vapour that passes through a fabric during a specific time period. Higher values imply greater vapour and moisture removal and the prevention of gas and vapour buildup. Under specified temperature and humidity, the MVTR is expressed in gram per square metre (g/m²) [18]. 

2. Techniques used for making breathable fabric

Based on the techniques employed in the multilayer construction, breathable components may be divided into several categories. To support a membrane and/or coating, it is important to have an appropriate substrate. However, in other instances such as close weaving construction, a single fabric can be utilized alone [51].

2.1 Close weaving

Both intra- and inter-yarn gaps in tightly woven textiles should be as tiny as possible to provide optimum protection against wind and rain. At the same time, the fabric outer surface should be non-absorbent and hydrophobic to prevent soaking out by rain or snow. As a result, the outerwear fabric must invariably strike a balance between waterproofness, wind resistance, and water vapour transfer characteristics [33].

Among the breathable textiles in this category are:

• Ventile: The Shirley Institute of the United Kingdom produced the world’s first breathable woven fabric using fine, long-staple Egyptian cotton fibres. Dense Oxford constructions, i.e. plain weave with warp threads running in pairs, were woven using low twisted, mercerized combed yarns. Ventile fabric, which features 10μm inter-yarn holes termed macropores, is not waterproof in itself. Still, when it comes into contact with water, the cotton fibres expand and reduce the inter-yarn pores to 3–4μm, preventing liquid water from passing through. Depending on the use, the cloth weighs between 170 and 295 gram per square metre and may guard against water penetration for up to 20 minutes [16].
• Microdenier synthetic filaments/fibres: High-density textiles, such as taffeta and Oxford weave fabrics provide excellent breathability due to thin and smooth threads tightly woven (7000 filaments/cm) into the fabric. Since microfibers are used, the pores in a cloth are incredibly tiny, even after it’s completely drained of moisture and dried. Compared to laminates and coatings, this weaving method produces a windproof fabric with high water vapour permeability [47]. As a result, these textiles are more resistant to water than cotton ventile and have a very soft hand. They are typically treated with silicones or fluorochemicals to make them water-repellant. This category of fabrics is released under the brand names Teijin Ellettes® and Unitika Gymstar® [48].

2.2 Microporous membranes and coatings

An ultra-thin polymeric film, 10μm is designed to prevent liquid water penetration, yet enable water vapour. The membrane is usually laminated with a conventional textile fabric [34]. Water droplets cannot pass through the micropores of the films and coatings, whereas moisture vapour molecules are forced through them. The micropores (0.02–1μm) are significantly smaller than the tiniest water droplets (100μm) [35]. Micropores allow water vapour molecules (of diameter <40×10−6μm) from sweating to pass through and fade away via a capillary mechanism [19]. A structure’s porosity, thickness and pore size have been demonstrated to affect water vapour transfer rates. Moisture vapour transfer through a surface with a fixed porosity and thickness rises as the porosity decreases. Water vapour permeability reduces with increasing cloth thickness [54].  The first best-known membrane is Gore-Tex®, a thin sheet of expanded polytetrafluoroethylene (PTFE) polymer with 1.4 billion microscopic pores per square cm, developed and released in 1976 by W Gore. In addition, Entrant®, manufactured by Toray Industries and Porelle®, made by Porvair, are other microporous polyurethane films available. Membranes made from microporous polyvinylidene fluoride (PVDF) can also be found [23].

Figure 3 Electron microscope photography of PTFE microporous film

A typical membrane is bonded to a standard textile fabric of around 10μm thickness for mechanical strength. On the other hand, coatings are far thicker than membranes, and their application method is also very different but their structure is similar. Membranes laminated to fabrics or porous coatings have pores of 0.1 to 50μm. Acrylics and poly(tetrafluoroethylene) coatings are the most often utilized (amino-acids). There are many other types of polymers available. Still, polyurethane is the most common because of its hardness, flexibility, abrasion resistance and the option of modifying characteristics as per end-use [28]. The first method involves embedding a permanent network of microscopic holes and passages in the polymer film or coating. The waterproof qualities of the fabric are typically acceptable if the greatest pore size at the outer surfaces of the barrier layer is 2 to 3μm or less. The microporous structure is permeable to air and allows water vapour to pass through at acceptable rates. On the other hand, microporous breathable textiles can be treated with a water-repellent treatment (e.g., fluorocarbons or silicones) to prevent the pores from being clogged and maintain a constant performance[48]. Following are some of the different ways for making microporous membranes and coatings [44]:

● Foam Coating – only for coatings

● Mechanical Fibrillation – only for membranes

● Meltblown Technology

● Nanofibrous web

● Point Bonding Technology

● Radio Frequency/ Ion/ UV/ Electron Beam Radiation

● Solubilising one Component in Mixture – only for coatings

● Solvent Extraction

● Thermocoagulation – only for coatings

● Wet Coagulation

Figure 4 Water vapour transfer through microporous (a) and hydrophilic (b) membranes: 1, water vapour molecules, 2. polymer molecular chains, 3. active hydrophilic groups, 4. water droplet

2.3 Hydrophilic membranes and coatings

Nonporous films that breathe through osmotic potential by adsorbing or desorbing vapour molecules and then transporting them to the other side are known as hydrophilic membranes. The phenomenon is similar to cells in the human body enabling monomolecular and ionic species to diffuse across their membrane walls. The difference in water vapour pressure between the two faces of the membrane provides the driving force for water vapour transfer. The process of Adsorption–diffusion–desorption in hydrophilics is thus the breathability, accelerated by hydrogen bonding between water molecules and functional groups incorporated into the molecular chains[40]. Firstly the water vapour molecules get adsorbed on the surface, occupying empty space between the polymer molecular chains, and then traverse the membrane without chemical interaction. Water vapour molecules can flow through amorphous regions but liquid water cannot because of the solid nature of the membrane. Vapour molecules interact with both the active hydrophilic groups and their surroundings with active hydrophilic groups. Membrane dissolution allows them to diffuse across, a process called activated diffusion. When they arrive at the opposite membrane’s surface, they are desorbed and released into the surrounding [19]. 

Hydrophilic functional groups are included in polymers, such as -O, CO, OH or NH2 in a block copolymer, leading to water vapour diffusion. There are no polar groups in the traditional coatings such as PVC, polyurethane, and rubbers that activate the hydrophilic mechanism for water transportation. Polyether groups have been added to the surface of Akzo’s Sympatex® to provide it hydrophilic characteristics. Many hydrophilic polymers, such as polyvinyl alcohol, are accessible. Still, they are very sensitive to water and would dissolve or expand so much that their flexibility and abrasion resistance would be poor without cross-linking[45]. As a result, an appropriate hydrophilic polymer for coating should have enough swelling to enable the passage of water vapour, while at the same time maintaining acceptable film strength. Hydrophilic–hydrophobic balance must be optimised for the film to work properly. Also, when the coatings are put at greater additions to obtain waterproofing on a par with laminates, a reduction in breathability can be noticed with the methods as mentioned earlier. Coatings are less costly and simpler to handle than thin film laminates[47]. A few benefits of hydrophilic films over microporous ones are listed below: 

• To prepare microporous materials using the wet-coagulation process requires the use of coagulation tanks, washing lines and dimethyl formamide (DMF) recovery facilities. For maximum breathability and waterproofness, careful control over the coating procedure is also necessary. On the other hand, hydrophilic coatings may be applied using standard solvent coating equipment [29]. 
• Microporous textiles with breathable characteristics can be affected by contaminants such as body oils, particulates of dirt, pesticide residues, insect repellents, sun tan lotion, salt, and residual detergent and surfactant residues used in cleaning. As a result, micropores can become enlarged when garments are stretched at the elbow and knee. On the other hand, hydrophilic films and coatings do not lose their characteristics when cleaning and stretching clothes, and are durable and easy to maintain. Sympatex® (by Sympatex Technologies) is waterproof and breathable, even after stretching up to 300 percent. In some cases, a hydrophilic coating is placed on microporous films to improve the water resistance of such films[50].
• Hydrophilic polyurethane coatings adhere well to textile substrates, have a high gloss, are resistant to water and solvents, and have a high moisture permeability property. They are also less costly. When a layer of condensation covers the surface of a microporous membrane, it is anticipated that it would perform less effectively. On the other hand, solid film hydrophilic films teffectively carry water without requiring re-evaporation. Condensation results in a high water content in the polymer, which plasticizes and swells the polymer, enhancing water vapour transfer at relatively high temperatures. Low temperatures, on the other hand, negate the benefits of plasticisation, thus the lining material should be chosen carefully [13].

Figure 5 Scanning electron micrograph of microporous membrane: (a) hydrophilic surface layer; (b) hydrophilic layer partly removed showing PTFE layer

• When used in microporous films, surfactants are known to induce leakage but not in hydrophilic films.
• Hydrophilic films have a wide spectrum of chemical and solvent resistance and good smell barrier characteristics. They can also act as barriers against some microorganisms. Thinner films produce more supple laminates with a handling closer to the original single layer textile. Also, they can have higher levels of breathability than microporous laminates [14].

Hydrophilic films and coatings do have certain drawbacks, which include:

• Vapour reservoir required for laminate to start breathing.
• The laminate tends to get clammy when wet.
• Wet laminates may produce ‘noise’ due to friction between film and fabric layers [38].

2.4 Combination of microporous and hydrophilic membranes and coatings

As indicated below, bicomponent microporous films provide several benefits over pure microporous films [35]:

• It gives the film more toughness and strength.
• The microporous base is sealed by a hydrophilic layer, preventing water from leaking through pinholes or large pores.
• It minimizes strain, leading to pores opening and water may infiltrate through.
• It has the resistance to penetration through some solvents or light mineral oils and attributes of windproofness
• Moisture vapour transfer occurs more through ‘mechanical’ than ‘chemical’ adsorption mechanisms.
• In some situations, it produces a laminate devoid of rubbing noise when wet, compared to solid hydrophilic membrane textiles.
• The construction of two-ply laminated textiles provides a lower frictional contact between the film and the sewing table.

            The inclusion of bicomponent microporous film, on the other hand, raises the laminate’s cost and rigidity while lowering the fabric’s overall breathability [40].

2.5 Using retroreflective microbeads

The textiles are printed or coated with a retroreflective ink or coating to create retroreflective fabrics. Microbeads hemispherically coated with aluminium are found in the ink coating of some textiles. Several hundred light transmissive microbeads, ranging in size from 20 to 90 micrometres, are included in each millimetre printing dot. Some microbeads might be retroreflective because they are irregularly positioned throughout the printing or coating process. It is solid in effect, but leaves uncoated regions which allow the fabric to ‘breathe’ and/or regulate moisture [51].

2.6 Smart breathable fabrics

A major advance in textile applications has been the development of clever waterproof breathable fabrics employing shape memory polymers. During low temperatures, the fabric prevents the loss of body heat by preventing the transfer of vapour or heat. In contrast, during hot temperatures, the fabric transmits more heat and water vapour from the inside of the garment to the outside [20]. Smart breathable textiles are constructed from these polymers, which serve as a switch to control the passage of water vapour from the skin to the air.  When temperature increases coating substance on the fabric is swelled (due to the absorption of water from the surrounding environment) and microcracks or micropores are sealed. On the contrary, a decrease in temperature leads to the prevalence of hydrophobic interactions in a collapsed form, resulting in microcrack opening. A shift in diffusion flux, which is regulated by changes in the diffusion coefficient and the diffusion route of water molecules through the inflated and deflated coating, may also impact. The diffusion flux is expected to decrease at a lower temperature than at a higher temperature due to these two variables [9].

For example, the US Army’s Soldier and Biological Chemical Command Laboratory in Natick, Massachusetts, created an amphibious diving suit that keeps the wearer comfortable both in and out of the water. The amphibious diving suit prevents water from contacting the skin while in the water, yet once out of the water, its innovative three-layer membrane construction enables perspiration to leave, reducing overheating. A temperature-sensitive copolymer like polypropylene may also be used to create smart breathable cotton textiles (N-tert- butylacrylamide-ran-acrylamide: 27:73) [42]. The textiles are coated with an aqueous solution (20 wt%) of the copolymer comprising 1,2,3,4-butanetetracarboxyl acid as a cross-linker (50 mol%) and sodium hydrophosphite (0.5 wt%) as a catalyst, then dried at 120 °C for 5 minutes. In the temperature range of 15–40 °C, the textiles show temperature-sensitive swelling behaviour. Biomimetics is another unique invention in smart breathable fabric. Biomimetics is the process of modifying biological systems to create useful artificial objects. Fabric coverings can increase water vapour permeability by adding an analogue of the leaf stomata, which open when the plant wants to promote moisture vapour transpiration and shut when it needs to decrease it [23]. As mentioned below, there are currently numerous breakthroughs in the domain of waterproof breathable textiles based on biomimetics:

2.6.1 The pine cone effect

Adaptive textiles that respond to humidity levels in a microenvironment increase breathability as the material becomes saturated [24]. It shuts to prevent moisture from entering and opens when the air is dry to flow through the vent. This technique may be utilised to create fabrics with better waterproof breathability. London College of Fashion researchers have revealed attempts to develop biomimetic clothes that may operate similarly. Small spikes, only 1/200th of a millimetre broad, may be added to the fabric’s surface to give it more traction. Hot weather opens the spikes to release heat and cool the user. In winterthe spikes flatten to trap air and give greater insulation [11].

Figure 6 Open and closed spines of a pine cone

Nike’s ‘Macro React’ line features a fish-scale design with a similar effect. Tennis player Maria Sharapova wore it for the first time at the US Open in 2006, and Roger Federer wore it at Wimbledon in 2008. Swinging flaps in cloth allow heat and moisture to escape during sweat, keeping the user dry and comfortable. AeroReact is a revolutionary responsive, lightweight athletic fabric. As the runner’s body temperature changes the cloth adapts to it. Bi-component yarn recognises moisture vapour and opens its structure for maximum breathability during physical activity [38].

MMT Textiles developed INOTEKTM fibres that make use of the pine cone effect. This is achieved by increasing the permeability of yarns and fabrics when moisture builds up around them, therefore reducing the damp feeling. Moisture causes fibres to shut (mimicking the pine cone) and shrink in volume, reducing the cross-section of the yarn. In the textile, microscopic air spaces are opened, increasing its breathability. In dry circumstances, the fibres return to their natural form, lowering air permeability and increasing the insulation of the textile material. INOTEKTM fibres are used in everyday clothing, sportswear, and base layers [55].

 2.6.2 Transpiration within a leaf effect

Transpiration is the mechanism through which plants lose water vapour through their stomata. When the weather is particularly hot, the loss of water vapour from the plant cools the plant, and water from the stem and roots flows upwards or is “drawn” into the leaves. Dehydrated mesophyll cells release the plant hormone abscisic acid when there is less water available for the plants, which causes the stomatal apertures to shut, reducing water loss during oxygen release and carbondioxide absorption. Stomatex® is a neoprene fabric with foam insulation that includes many small hole-like domes that operate similarly to the transpiration process within a leaf and allow a regulated release of water vapour to keep the garment comfortable. When the user is at rest, Stomatex® is said to adapt to the degree of activity by pumping faster as more heat is created, then reverting to a more passive state. Stomatex® can work with the Sympatex® system [2].

Figure 7 (a) Transpiration effect in plants; (b) AKZO NOBEL’s Stomatex® fabric based on transpiration effect

2.6.3 The lotus flower surface effect

By mimicking the structure of a lotus leaf, the Teijin Company in Japan created Super-Microft®, a fabric with exceptional water repellency. Water cascades like mercury off the lotus leaf’s microscopically rough surface, which is coated in a waxy material with low surface tension. Super-Microft® has been found to have strong water-repellent durability and a high wear resistance while also having moisture permeability and waterproof properties [24].

3. Membrane integration and coating application methods in the layered manufacturing of breathable textiles

Microporous or hydrophilic membranes are delicate and lack a cloth-like texture. They must be implemented into textile goods so that the desired ‘high-tech’ function is maximised but the traditional textile qualities of handling, drape, and aesthetic impression are not harmed. The textiles will be two-, three-, or four-layered, with the breathable membrane coated or laminated on one of the layers. Membranes may be incorporated into textiles in four different ways [35].

The breathable membrane or coating may be laminated with the following layers:

• the exterior layer (inner or outer face),
• the middle layer,
• the inner layer,
• both the inner and outer layers in some situations.

Out of these, the last is rarely used but the second provides best results in terms of handle and drape. Moreover, second and third methods provide flexibility for the garment manufacturer as the outer fabric can be modified to suit fashion demands. The lamination methods may be different depending on the intended application. The last one is rarely used, while the second one gives the greatest results in terms of handling and drape. Furthermore, the second and third techniques provide the garment maker more freedom because the exterior fabric may be changed to meet fashion needs. Several lamination techniques may be used [30]. Due to enhanced efficiency, durability, environmental and energy considerations these materials melt at around 130°C and produce a cross-linked adhesive bond. Reifenhauser has reported an improved and less expensive technique of creating breathable waterproof film/nonwoven laminates using a combined film extrusion and laminating process. Rather than utilising mechanical pressure, this technique includes the coating via an electrostatic process [41]. The lamination technique must be carefully designed to guarantee that the laminate’s breathability is maintained at a high degree. In addition to the films that have been created for a range of machines, modifications to laminators’ adhesive requirements to improve fabric laminate performance have been made in response to environmental concerns and customer desire [43].

The substrate on which the membrane must be laminated varies by application and includes: 

• Woven textiles for clothing and wound treatments
• Wound dressings, inserts/linings, and roofing membranes all use nonwovens
• Upholstery foams are a type of foam that is used to cushion furniture

For various reasons, nonwovens have shown to be more cost effective than conventional textiles. MediSoft® (product of Polymer Group Inc., Netherlands), for example, is a patented spunmelt product improved with softness and breathability, thanks to a combination of spunmelt and spunlace characteristics. Another invention is DuPontTM Acturel®, which comprises three layers: a polyester nonwoven inner layer, a breathable membrane layer called Dupont TM Hytrel®, and a spun-bonded polypropylene outer layer. The first two layers are created using an extrusion coating technique, and the final, outer layer is adhered to the Hytrel® layer using an adhesive laminate. Similarly, many nonwoven materials are transformed into breathable fabrics [15].

The traditional way of applying coating to cloth is to use a knife over roller technique for direct application. Several applications may be used to build up the coating in several layers. Transfer coating is used to create thinner coatings and therefore a more flexible fabric and, apply coating to warp-knitted, nonwoven, open weave, and elastic fabric. A film is also created in the transfer coating process by casting on a release paper, and then attached to the fabric to create laminates. The coating is applied to the fabric’s inside side, which will be the inside of the garment. These ‘regular’ coatings have high abrasion resistance, thus fabric lining is not required to protect the coated surface. Polyurethane may also be applied to knitted textiles by transfer coating to create considerably softer and more flexible coated fabrics, however in this case, the coating is applied to the side that would become the garment’s exterior. Cyclone (Carrington), Entrant TM (Toray), Keelatex, and other commercial products use the aforementioned technique [52].

As the interstices are blocked by the coating material in direct-coated textiles of the same fibre type, transfer coated and laminated fabrics are more permeable for a given polymer coating weight than direct-coated fabrics of the same fibre type [33]. VTREXTM (Vapour Attenuating and Expelling Thermal Retaining Insulation for Extreme Cold Weather Clothing) is a foul weather survival fabric that has been created. The insert layer of the composite construction is made of PU foam for greater thermal insulation. During use, the outer layer is coated to defend against bad weather conditions such as wind, rain, snowfall, or abrasion [22].

4. Performance evaluation of waterproof breathable fabrics

      Breathable fabrics are expected to meet many functional characteristics other than breathability in many applications, including fabric tear, tensile, and peel strength; flex and abrasion resistance; launderability; tape sealability; thermo-physiological comfort, and so on, and to perform well over the product’s lifetime [26]. Fabrics’ functionality can also be harmed by surface alteration or sewing. However, three characteristics are primarily measured when evaluating the performance of waterproof breathable textiles [23]:

• resistance of penetration and absorption of liquid water
• water vapour permeability
• wind resistance

Typical breathable textiles have the following properties [10]:

• Water vapour permeability – minimum 5000g/m2/24h
• Waterproofness–minimum130cm,hydrostaticpressure
• Windproofness – less than 1.5cm3/cm2/second at 1mbar; measured by air permeability.

Table 1 Tests with standards for evaluation of waterproof breathable fabrics

5. Applications of waterproof breathable fabrics

Table 2 demonstrates how waterproof breathable textiles may be used in a variety of situations. The term “breathability” is used in a broader sense in a number of applications. Depending on the nature of the application, the performance requirements of any breathable fabric might vary greatly [12]. For example, in a cold storage facility with temperatures ranging from 5 to 50 degrees Celsius, a fabric with strong heat resistance and breathable properties is required. However, fabrics should transfer a high amount of water vapour while shielding the body from external heat in a firefighting activity because the body perspires excessively [17]. Some emergency waterproof protective gear, commonly referred to as “foul weather apparel,” is manufactured to the highest performance levels for military, offshore workers, and civilians. Aside from wind, rain, and cold, the user must be protected from sharp item penetration, sun radiation, and heat stress. In biomedical applications, waterproof breathable textiles function as barriers against bacteria and other germs that are thought to be transferred from one area to another by patients’ and medical staff’ body fluids. In recent years, the potential dangers and contamination caused by viruses such as HIV, SARS, Ebola, and others have raised the protective needs for medical textiles [30, 36]. Clothing must be both protective and pleasant to maintain an energy balance within the limits of tolerance for heating and cooling the body. Apparel for outdoor vocations such as farming and construction and clothing for strenuous outdoor hobbies, require breathable materials (e.g. cycling and mountaineering). These materials are also employed in offshore protective gear, where the user is subjected to cold temperatures, wind, rain, and on rare occasions severe wind-driven rain [7]. Table 2 Applications of waterproof breathable fabrics

6. CONCLUSION

Breathable fabrics allow for the passive passage of water vapour through diffusion but do not enable liquid water to pass through. As a result, they aid cooling through perspiration evaporation [8]. In the realm of breathable waterproof textiles and clothing, there is a lot of research and development going on, with cost performance and end-use being significant aspects. Lightweight textiles and clothing and smart (intelligent) materials, are on the rise [53]. Smart textiles (for example, phase change materials), nanotechnologies, and biomimetics are promising topics for the next generation of waterproof breathable fabrics. Venting and core comfort mapping are two emerging developments in producing breathable and waterproof clothing,” with garments being created to meet the diverse functional requirements of various areas of the human body [42]. Eco-friendly treatments (e.g. perfluoro octanoic acid-free fluoro-chemical finishes) and ecologically friendly and recyclable textiles and clothing are also on the rise [4].

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