What are textiles?

A textile is a flexible material consisting of a network of natural or artificial fibers (yarn or thread). Yarn is produced by spinning raw fibers of wool, flax, cotton, hemp, or other materials to produce long strands. Textiles are formed by weaving, knitting, crocheting, knotting, felting, or braiding.

The related words "fabric" and "cloth"are often used in textile assembly trades (such as tailoring and dressmaking) as synonyms for textile. However, there are subtle differences in these terms in specialized usage. A textile is any material made of interlacing fibers, including carpeting and geo textiles. A fabric is a material made through weaving, knitting, spreading, crocheting, or bonding that may be used in production of further goods (garments, etc.). Cloth may be used synonymously with fabric but is often a piece of fabric that has been processed

History
The first clothes, worn at least 70,000 years ago and perhaps much earlier, were probably made of animal skins and helped protect early humans from the ice ages. Then at some point people learned to weave plant fibers into textiles.

The discovery of dyed flax fibres in a cave in the Republic of Georgia dated to 34,000 BCE suggests textile-like materials were made even in prehistoric times.


The production of textiles is a craft whose speed and scale of production has been altered almost beyond recognition by industrialization and the introduction of modern manufacturing techniques. However, for the main types of textiles,

plain weave, twill, or satin weave, there is little difference between the ancient and modern methods.


Uses
Textiles have an assortment of uses, the most common of which are for clothing and for containers such as bags and baskets. In the household they are used in carpeting, upholstered furnishings, window shades, towels, coverings for tables, beds, and other flat surfaces, and in art. In the workplace they are used in industrial and scientific processes such as filtering. Miscellaneous uses include flags, backpacks, tents, nets, handkerchiefs, cleaning rags, transportation devices such as balloons, kites, sails, and parachutes; textiles are also used to provide strengthening in composite materials such as fibreglass and industrial geotextiles. Textiles are used in many traditional crafts such as sewing, quilting and embroidery. Textiles for industrial purposes, and chosen for characteristics other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles (e.g. implants), geotextiles (reinforcement of embankments), agrotextiles (textiles for crop protection), protective clothing (e.g. against heat and radiation for fire fighter clothing, against molten metals for welders, stab protection, and bullet proof vests). In all these applications stringent performance requirements must be met. Woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of "self-powering nanosystems" using vibrations created by everyday actions like wind or body movements.

Sources and types

Textiles are made from many materials, with four main sources: animal (wool, silk), plant (cotton, flax, jute), mineral (asbestos, glass fibre), and synthetic (nylon, polyester, acrylic). The first three are natural. In the 20th century, they were supplemented by artificial fibres made from petroleum.
Textiles are made in various strengths and degrees of durability, from the finest microfibre made of strands thinner than one denier to the sturdiest canvas. Textile manufacturing terminology has a wealth of descriptive terms, from light gauze-like gossamer to heavy grosgrain cloth and beyond.

Animal

Animal textiles are commonly made from hair, fur, skin or silk (in the silkworms case).
Wool refers to the hair of the domestic goat or sheep, which is distinguished from other types of animal hair in that the individual strands are coated with scales and tightly crimped, and the wool as a whole is coated with a wax mixture known as lanolin (sometimes called wool grease), which is waterproof and dirtproof.Woollen refers to a bulkier yarn produced from carded, non-parallel fibre, while worsted refers to a finer yarn spun from longer fibres which have been combed to be parallel. Wool is commonly used for warm clothing. Cashmere, the hair of the Indian cashmere goat, and mohair, the hair of the North African angora goat, are types of wool known for their softness.
Other animal textiles which are made from hair or fur are alpaca wool, vicuña wool, llama wool, and camel hair, generally used in the production of coats, jackets, ponchos, blankets, and other warm coverings. Angora refers to the long, thick, soft hair of the angora rabbit. Qiviut is the fine inner wool of the muskox.
Wadmal is a coarse cloth made of wool, produced in Scandinavia, mostly 1000~1500 CE.
Sea silk is an extremely fine, rare, and valuable fabric that is made from the silky filaments or byssus secreted by a gland in the foot of pen shells.
Silk is an animal textile made from the fibres of the cocoon of the Chinese silkworm which is spun into a smooth fabric prized for its softness. There are two main types of the silk: 'mulberry silk' produced by the Bombyx Mori, and 'wild silk' such as Tussah silk. Silkworm larvae produce the first type if cultivated in habitats with fresh mulberry leaves for consumption, while Tussah silk is produced by silkworms feeding purely on oak leaves. Around four-fifths of the world's silk production consists of cultivated silk.

Plant

Grass, rush, hemp, and sisal are all used in making rope. In the first two, the entire plant is used for this purpose, while in the last two, only fibres from the plant are utilized. Coir (coconut fibre) is used in making twine, and also in floormats, doormats, brushes, mattresses, floor tiles, and sacking.
Straw and bamboo are both used to make hats. Straw, a dried form of grass, is also used for stuffing, as is kapok.
Fibres from pulpwood trees, cotton, rice, hemp, and nettle are used in making paper.
Cotton, flax, jute, hemp, modal and even bamboo fibre are all used in clothing. Piña (pineapple fibre) and ramie are also fibres used in clothing, generally with a blend of other fibres such as cotton. Nettles have also been used to make a fibre and fabric very similar to hemp or flax. The use of milkweed stalk fibre has also been reported, but it tends to be somewhat weaker than other fibres like hemp or flax.
The inner bark of the lacebark tree is a fine netting that has been used to make clothing and accessories as well as utilitarian articles such as rope.
Acetate is used to increase the shininess of certain fabrics such as silks, velvets, and taffetas.
Seaweed is used in the production of textiles: a water-soluble fibre known as alginate is produced and is used as a holding fibre; when the cloth is finished, the alginate is dissolved, leaving an open area.
Lyocell is a synthetic fabric derived from wood pulp. It is often described as a synthetic silk equivalent; it is a tough fabric that is often blended with other fabrics – cotton, for example.
Fibres from the stalks of plants, such as hemp, flax, and nettles, are also known as 'bast' fibres.

Mineral

Asbestos and basalt fibre are used for vinyl tiles, sheeting and adhesives, "transite" panels and siding, acoustical ceilings, stage curtains, and fire blankets.
Glass fibre is used in the production of ironing board and mattress covers, ropes and cables, reinforcement fibre for composite materials, insect netting, flame-retardant and protective fabric, soundproof, fireproof, and insulating fibres. Glass fibres are woven and coated with Teflon to produce beta cloth, a virtually fireproof fabric which replaced nylon in the outer layer of United States space suits since 1968.
Metal fibre, metal foil, and metal wire have a variety of uses, including the production of cloth-of-gold and jewellery. Hardware cloth (US term only) is a coarse woven mesh of steel wire, used in construction. It is much like standard window screening, but heavier and with a more open weave.
Minerals and natural and synthetic fabrics may be combined, as in emery cloth, a layer of emery abrasive glued to a cloth backing. Also, "sand cloth" is a U.S. term for fine wire mesh with abrasive glued to it, employed like emery cloth or coarse sandpaper.

Synthetic

Synthetic textiles are used primarily in the production of clothing, as well as the manufacture of geotextiles.
Polyester fibre is used in all types of clothing, either alone or blended with fibres such as cotton.
Aramid fibre (e.g. Twaron) is used for flame-retardant clothing, cut-protection, and armour.
Acrylic is a fibre used to imitate wools, including cashmere, and is often used in replacement of them.
Nylon is a fibre used to imitate silk; it is used in the production of pantyhose. Thicker nylon fibres are used in rope and outdoor clothing.
Spandex (trade name Lycra) is a polyurethane product that can be made tight-fitting without impeding movement. It is used to make activewear, bras, and swimsuits.
Olefin fibre is a fibre used in activewear, linings, and warm clothing. Olefins are hydrophobic, allowing them to dry quickly. A sintered felt of olefin fibres is sold under the trade name Tyvek.
Ingeo is a polylactide fibre blended with other fibres such as cotton and used in clothing. It is more hydrophilic than most other synthetics, allowing it to wick away perspiration.
Lurex is a metallic fibre used in clothing embellishment.
Milk proteins have also been used to create synthetic fabric. Milk or casein fibre cloth was developed during World War I in Germany, and further developed in Italy and America during the 1930s.Milk fibre fabric is not very durable and wrinkles easily, but has a pH similar to human skin and possesses anti-bacterial properties. It is marketed as a biodegradable, renewable synthetic fibre.
Carbon fibre is mostly used in composite materials, together with resin, such as carbon fibre reinforced plastic. The fibres are made from polymer fibres through carbonization.

Production methods

Top five exporters of textiles—2013 ($ billion)
China	274
India	40
Italy	36
Germany	35
Bangladesh	28

Weaving is a textile production method which involves interlacing a set of longer threads (called the warp) with a set of crossing threads (called the weft). This is done on a frame or machine known as a loom, of which there are a number of types. Some weaving is still done by hand, but the vast majority is mechanized.
Knitting, looping, and crocheting involve interlacing loops of yarn, which are formed either on a knitting needle, needle, or on a crochet hook, together in a line. The processes are different in that knitting has several active loops at one time, on the knitting needle waiting to interlock with another loop, while Looping and crocheting never have more than one active loop on the needle. Knitting can be performed by machine, but crochet can only be performed by hand.
Spread Tow is a production method where the yarn are spread into thin tapes, and then the tapes are woven as warp and weft. This method is mostly used for composite materials; spread tow fabrics can be made in carbon, aramide, etc.
Braiding or plaiting involves twisting threads together into cloth. Knotting involves tying threads together and is used in making macrame.
Lace is made by interlocking threads together independently, using a backing and any of the methods described above, to create a fine fabric with open holes in the work. Lace can be made by either hand or machine.
Carpets, rugs, velvet, velour, and velveteen are made by interlacing a secondary yarn through woven cloth, creating a tufted layer known as a nap or pile.
Felting involves pressing a mat of fibres together, and working them together until they become tangled. A liquid, such as soapy water, is usually added to lubricate the fibres, and to open up the microscopic scales on strands of wool.
Nonwoven textiles are manufactured by the bonding of fibres to make fabric. Bonding may be thermal or mechanical, or adhesives can be used.
Bark cloth is made by pounding bark until it is soft and flat.

Treatments

Textiles are often dyed, with fabrics available in almost every colour. The dyeing process often requires several dozen gallons of water for each pound of clothing.Coloured designs in textiles can be created by weaving together fibres of different colours (tartan or Uzbek Ikat), adding coloured stitches to finished fabric (embroidery), creating patterns by resist dyeing methods, tying off areas of cloth and dyeing the rest (tie-dyeing), or drawing wax designs on cloth and dyeing in between them (batik), or using various printing processes on finished fabric. Woodblock printing, still used in India and elsewhere today, is the oldest of these dating back to at least 220 CE in China. Textiles are also sometimes bleached, making the textile pale or white.

Textiles are sometimes finished by chemical processes to change their characteristics. In the 19th century and early 20th century starching was commonly used to make clothing more resistant to stains and wrinkles.
Eisengarn, meaning "iron yarn" in English, is a light-reflecting, strong material invented in Germany in the 19th century. It is made by soaking cotton threads in a starch and paraffin wax solution. The threads are then stretched and polished by steel rollers and brushes. The end result of the process is a lustrous, tear-resistant yarn which is extremely hardwearing.
Since the 1990s, with advances in technologies such as permanent press process, finishing agents have been used to strengthen fabrics and make them wrinkle free. More recently, nanomaterials research has led to additional advancements, with companies such as Nano-Tex and NanoHorizons developing permanent treatments based on metallic nanoparticles for making textiles more resistant to things such as water, stains, wrinkles, and pathogens such as bacteria and fungi.
Textiles receive a range of treatments before they reach the end-user. From formaldehyde finishes (to improve crease-resistance) to biocidic finishes and from flame retardants to dyeing of many types of fabric, the possibilities are almost endless. However, many of these finishes may also have detrimental effects on the end user. A number of disperse, acid and reactive dyes (for example) have been shown to be allergenic to sensitive individuals. Further to this, specific dyes within this group have also been shown to induce purpuric contact dermatitis.
Although formaldehyde levels in clothing are unlikely to be at levels high enough to cause an allergic reaction, due to the presence of such a chemical, quality control and testing are of utmost importance. Flame retardants (mainly in the brominated form) are also of concern where the environment, and their potential toxicity, are concerned. Testing for these additives is possible at a number of commercial laboratories, it is also possible to have textiles tested for according to the Oeko-tex certification standard which contains limits levels for the use of certain chemicals in textiles products.

Introduction to breathable water-repellent textiles and their production methods

Type of Breathable textile materials | Methods of producing Breathable textiles

Breathability refers to the ability of a fabric to absorb moisture and release it through the material itself, allowing it to ‘breathe’. Breathable Fabrics transmit body moisture away from the body, thus maximizing comfort and dryness during outdoor activities.

Waterproof Vs. Water Repellent Vs. Water Resistant

This looks above three terms are alike but there is a difference between waterproof, water repellent and water resistant. We must at the very beginning distinguish between “waterproof” and “water-repellent” textile surfaces.  When you start to add breathability into the mix, things can start to get a little complicated. So, you should have clarified what do they all mean and why should you take note of the differences?

Definitions

Waterproof

1. Waterproof fabrics are fabrics that are inherently or have been treated to become, resistant to penetration by water and wetting. The term “waterproof” refers to conformance to a governing specification and specific conditions of a laboratory test method.
   Even when you put pressure on a waterproof garment, it will still be impervious to water. The amount of pressure you can put on the garment before you start to get wet varies, and you can find out what that amount is by checking the garment’s water column.

Water Repellent

Water-repellent treatment is a standard finishing process for modern textiles in order to create breathable textiles. Water-repellent agents exploit the high-water repellency of silicones without impairing the textiles’ ability to breathe. Additionally, they confer a soft hand on textiles.

Water repellency is, therefore, a step up from water resistance. This means that water can’t easily penetrate the material (the technical term is that it’s hydrophobic).

Meaning:

• Not easily penetrated by water, especially as a result of being treated for such a purpose with a surface coating.  It beads on the outside instead. The fabric is a densely woven and it offers some water resistance.
• Adjective (of fabrics, garments, etc) having a finish that resists the absorption of water
• Adjective having a finish that resists but is not impervious to water.
• Water-repellent clothing or material does not absorb water when it is raining lightly
• Able to keep rain from being absorbed.

Water Resistant

This offers the lowest level of water protection. If a garment resists water, it’s usually because the fabric itself is acting as a barrier between you and a light shower. Tightly woven fabrics will offer a degree of water resistance, as it takes some time for the water to seep through the material.

Adjective

1. Able to resist the penetration of water to some degree but not entirely
2. Resisting though not entirely prevent the penetration of water.

The Definition of Breathability

In a nutshell, breathability refers to the ability of a fabric to absorb moisture and release it through the material itself, allowing it to ‘breathe’. Breathable means that a fabric permits perspiration vapors to escape from the body through the fabric. During strenuous activity, the body releases moisture vapors, and the skin breathes this moisture as it naturally tries to cool itself down.

Breathable Fabrics transmit body moisture away from the body, thus maximizing comfort and dryness during outdoor activities. This continuous cycle of motion is at the heart of the mechanism of breathability: the more you sweat inside a breathable clothing item, the higher its perspiring capacity should be, and this circular action never stops.

Breathability does not, as the term might imply, relate to an exchange of air. Instead, it is the ability of a fabric to allow moisture vapor to pass through it. A fabric may carry this out in numerous different ways, and exchange of air is only one possible avenue. Moisture vapor permeability (MVP) and moisture vapor transmission (MVT) are perhaps better, and certainly more technical, terms to use than breathability. Neither ASTM nor the Textile Institute defines breathability, but MVP and MVT are both defined in test standards.

Air permeability is intrinsically linked to breathability. Air permeability is “the velocity of an air flow passing perpendicularly through a test specimen under specified conditions of the test area, pressure drop, and time” (according to BS EN ISO 9237: 1995). All air permeable fabrics are breathable to some extent, though not all breathable fabrics are air permeable.

Application of durable water-repellent finishes by coating methods

Measuring the surface tension of the liquid, one may calculate the work of adhesion between the liquid and the surface of the solid. It is clear that the smaller the work of adhesion, the smaller will be the wettability and the greater will be the repellency.

What is water repellent finish?

The durability of Water-Repellent Finishes

Durable water repellent, or DWR, is a coating added to fabrics at the factory to make them water-resistant (or hydrophobic). Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as Gore-Tex to prevent the outer layer of fabric from becoming saturated with water.

A durable water repellent (DWR) is a functional finish for fabrics, which adds water-shedding properties to existing products. Garments treated with a DWR bead water droplets and force water to roll off the surface of the fabric.

The DWR, as the name suggests, repels water, i.e. water droplets form on the outer surface (as we stated above). And this plays an important role in breathability. When we say a jacket is “breathable”, we don’t actually mean it breathes. What we really mean is that it transports moisture – sweat – from the inside to the outside of the jacket.

For moisture to move from the inside to the outside but not the other way around, the face fabric can’t be soaked in water. As we stated above, hydrophilic fabrics on their own keep you dry from rain from the outside – as they soak it up – but they won’t keep you dry from your own sweat from the inside. So, it’s the combination of a hydrophilic material and a DWR that makes a jacket waterproof and breathable.

Hydrophilic fabrics are also impregnated with a durable water repellent (DWR). But if they inherently stop water reaching your skin, why do you need a DWR? Good question!

We did say this would get a little complicated! But what you need to take away from this is:

• Waterproofness is what you need to look for if you plan on wearing your gear in rainy or snowy conditions
• Breathability – i.e. transporting your sweat away from your skin – usually goes hand-in-hand with waterproofness
• Water repellency offers light rain resistance thanks to the impregnation
• Types of DWR Solutions
• Fluorine-free
• Fluorine-free DWR solutions are the future of water-repellency in the textile industry. These solutions contain no fluorochemicals, making them ultimate environmentally-friendly solutions for garments requiring water repellency.
• C8/C6: This solution is a chemical compound made up of carbon and fluorine atoms. These atoms form a long chain (C8), which helps repel water and oil from fabrics. Due to concerns from the Environmental Protection Agency (EPA) on fluorochemicals, mostly concerning toxicity and human contact, textile manufacturers have moved away from incorporating this technology into their garments.  The fundamental difference between the C6 solutions and C8 is that the C6 solution contains fewer fluorochemicals, reducing the hazardous risk.

How DWRs Work

DWRs work by increasing the “contact angle” or “surface tension” created when water contacts a textile. Basically, a high contact angle creates a microscopically “spiky” surface that suspends water droplets on the outer fringe of the fabric.

An optimized DWR keeps droplets in a rounded shape—like a dome-shaped bead. The rounder the droplet, the easier it rolls off the fabric. A low contact angle permits droplets to assume a flattering shape, one that can spread out like a splotch, cling to the fabric’s surface and eventually seep into it.

DWR Ratings

Manufacturers generally measure DWR effectiveness by a spray test. Water is sprayed onto a textile, and the amount that sticks is visually assessed. A score of 90 points indicated that roughly 90% of the fabric has no water sticking to it. The higher the number, the better the performance. The test is then repeated after a number of washings to determine durability.

Test scores and the number of washings is combined to create a rating. For example, a 90/10 rating means the spray test achieved a total of 90 points after 10 washes.

Not all manufacturers publish DWR performance ratings, but here is a basic guide for interpreting any that you find:

• Good: 80 points after 10 washes. This is a basic outerwear finish.
• Excellent: 80 points after 20 washes. Marmot, for example, uses this as its minimum rating for outerwear.
• Superior: 80 points after 50 to 100 washes.

Fabric Production process and coating techniques

Fabric requirements need tendency of to resist wetting is a function of the chemical nature of the solid surface, the roughness of the surface, the porosity of the surface, and the presence of other molecules on the surface. Woven fabrics for water repellent/ water resistant/breathable textiles feature permeable pore channels between yarn interlocking points (mesopores), which create an increased risk of penetration by contaminated fluids and particles. These pore channels can be reduced in size by finer count and high-density weaving.

This, however, results in deteriorated drapability and performance characteristics. The barrier properties of the woven fabric are determined by the construction-dependent pore morphology (mesopores and micropores), and the surface character of the textile structures.

When used for protective garments, it is equally important to guarantee high wearing comfort. Fulfilling these conflicting requirements (barrier effect and comfort) in a single textile structure is an immense challenge. To impede the penetration or pervasion of fluids, barrier textiles are finished with fluorocarbon (FC) resin.

The hydrophilizing by means of FC also reduces the adsorption of water on the fibers. Such woven fabrics only have an effective barrier function against fluids at small amounts of fluid, low pressures, and short exposure times. In the simplest case (sieve effect), the maximum pore sizes present in the woven fabric determines particle retention. In the case of smaller particles and larger pores, further barrier mechanisms are known, such as retention by bridging and by adhesive forces (van der Waals forces), or by electrostatic forces.

In microfilament woven fabrics, deep-bed filtration also plays an important role. Particles penetrating into the woven fabric interact with the filament surfaces and can be deposited between the woven fabric filaments. In order to fully exploit the advantages of woven fabrics as barrier textiles (good drapability, high wearing comfort), mesopores present primarily at the crossing points of warp and weft yarns in the woven fabric are to be reduced in size by a targeted finishing with fine microparticles so that the woven fabric meets the stated requirements.

Coating Methods

1. Knife Coating (floating knife) or Direct Coating

   In Knife Coating, as seen in Figure 3, the liquid coating is applied to the fabric while being run at tension under a floating knife blade, the distance between the fabric and the knife blade determines the thickness of the coating. The blade can be angled and have different profiles to affect the coverage. For this process to be effective the liquid coating must be quite viscous in order to prevent it from soaking through the fabric, the coating is then dried or cured.
   This technique is best used for Filament yarns as the staple fibers in spun yarns can protrude on the surface creating an uneven finish, but this is dependent upon the thickness of the applied coating. For this type of coating to be most successful the weave structure has to be quite tight and the fabric capable of being held taught.

   

   Figure 3. Fung, W, 2002, Coated and Laminated Textiles, UK; Woodhead Publishing;

2. Direct Roll Coating

   In this process, the coating liquid is rolled onto the fabric by a roller suspended in the coating solution, often a blade is positioned close to the roller to ensure not too much coating solution is applied.

   

   Figure 4. Direct Roll Coating from;Sen, A K, 2008, Coated Textiles; Principles and Applications, 2nd Edition, USA;Taylor and Francis.

3. Pad-Dry-Cure

   Also referred to as Padding, this technique, widely regarded as a textile finishing technique, can, in fact, be used to add a variety of coatings, but this usually refers to a fiber coating for the application of micro or nanomaterials or chemical compositions.
   As shown in figure 5, the fabric is submerged in the coating solution then the excess squeezed out in the rollers, which dictates the pick-up percentage, the fabric is then dried and cured.

   

   Figure 5

4. Calender coating

   Calender finishing involves the fabric passing through a set of heated rollers to singe off any surface fibers and add lustre and smoothness. Calender coating is the same principle in which the fabric passes through heated rollers, but through this process, a coating is applied as demonstrated in figure 6. This image demonstrates the simultaneous coating of both sides of the fabric with the thickness of the coating determined by the width of the nip in-between the rollers, more rollers used can provide a thinner coating.

   

   Figure 6. Depicts calender coating. Image from; TPO coated PP fabrics and their applications

5. Hot melt extrusion coating

   Hot melt extrusion coating is applied in the same process as calendaring with the coating being melted from granules fed to heated rollers which then nip the coating to the fabric. It is used to produce un-supported films and these freshly produced films are added directly to the fabric. Its uses are mainly for Thermoplastic polymers such as Polyurethane, Polyolefins, and PVC.

6. Foam Finishing

   Foam finishing was developed as a more environmentally friendly version of the pad-dry-cure system, as the chemical applied requires less product in weight, but equates to a high surface area. Foam also ensures lesser wetting takes place, which requires less drying; furthermore, waste is reduced in terms of residual liquor. This technique is useful in coating heavy fabrics such as carpets and can be used to effectively coat only one side.

Test Method of Specified Requirements of Water Repellency Textiles

Water Repellent Textiles

Water repellent fabrics are processed with water repellent additives so that water droplets form on the surface but do not penetrate the fabric, a phenomenon known as “the lotus effect.” The efficiency of water repellency is graded in 6 ratings as 0, 50, 70, 80, 90 and 100. A standard test is usually performed after five launderings with water at a temperature of forty degrees Celsius. To qualify as water repellent, the fabric must perform to at least rating four (90% or better efficiency). Further tests for the endurance of water repellency may be performed after 20, 50 or 100 launderings at similar temperatures to the initial test. Water Repellency Textiles are commonly used in fabrics for windbreakers outer garments, umbrellas, furniture decorations to name just a few.

Taiwan technology for Water Repellent Textiles achieves rating 100 initially, and not less than rating 80 after 100 launderings. The test method employed is AATCC 22. The Optical Contact Angle for lotus leaf is 135°; ordinary water-repellency treatments reach 130°; ordinary nano-treatments achieve 140°. However, with Taiwan’s special nano-technology for functional textiles, the Optical Contact Angle reaches up to 150°.

1. Scope

   This criterion defines the evaluation and testing of water repellency textiles. It is applicable to textiles with
   water-repellent finishes. However, it is not intended to measure penetration of water through the textiles.

2. Terminology

   Water repellency: the characteristic of textile to resist surface wetting.

3. Performance specification

   Grade classification
   100(ISO 5) Excellent
   90(ISO 4) Very Good
   80(ISO 3) Good
   70(ISO 2) —
   50(ISO 1) —
   0 —

4. Test Method

   Water Repellency

5. Test Specimens

   Three test specimens 180.0×180.0mm are needed and should be conditioned at 65+/-2% relative humidity and 20+/-2°C until moisture equilibrium.

6. Test Procedure

   • Fasten the test specimen securely in the 150+/-5 mm diameter hoop so that the face of the test specimen will be exposed to the water spray. The surface of the specimen should be smooth and without wrinkles. Place the hoop on the stand of the tester in 45° with the specimen uppermost in such a position that center of the spray pattern
     coincides with the center of the hoop. The distance should be 150+/-2 mm. Make sure that the warp direction of the test specimen should parallel to the watering direction.
   • Pour 250ml of distilled water into the funnel of the tester and allow it to spray onto the test specimen for 25 to 30 seconds. Take the hoop by the bottom edge and tap the opposite edge firmly once against a solid object with the fabric facing the object, then rotate the hoop 180° and tap once more on the point previously held.
   • Repeat the procedure above for other 2 specimens.
     
   • Evaluation and Report After tapping, immediately compare the wet or spotted pattern with the rating chart. Rate the face of the specimen. Report the worst rating.
   • Washing requirement: Select the specified washing condition and drying method based on the suppliers’ provided care instruction.
   • Fill the washing machine with water to 18Gal (about 68L) and adjust the water temperature. Machine Cycle Washing Temperature Drying Procedure (1) Normal/Cotton Sturdy (2) Delicate (3) Permanent Press (II) 27+/-3°C
     (80+/-5°F) (III) 41+/-3°C (105+/-5°F) (IV) 49+/-3°C (120+/-5°F) (V) 60+/-3°C (140+/-5°F) (A) Tumble i. Cotton Sturdy ii. Delicate iii. Permanent Press (B) Line (C) Drip (D) Screen
   • Add 66+/-1g of 1993 AATCC Standard Reference Detergent to the washing machine. Then, add the test specimens and ballast (total weight: 1.8+/-0.1kg) into the machine. Set the washer for the selected washing cycle and time.
   • Remove the specimen after the final spin and dry the specimen according to the specified method. After drying, condition the specimens by laying each specimen separately on the screen in an atmosphere of 20+/-2°C and 65+/-2%
     RH. until it achieves moisture equilibrium.
     

Summary and Conclusions

The theory of water repellency of textile fabrics has been reviewed with special references to the more recent theory of the wetting of fabrics by water. A survey has also been made on the various testing methods that have been devised for measuring water repellency. The results of the present investigation lead to the following conclusions regarding the status of water repellency. There is a definite need for a comprehensive study of the role that the structure of a fabric plays in the phenomena of water repellency. Students can take these projects and develop the products in their workshops, chemical laborite and test them in the testing laboratory.

In the past, the emphasis has been on developing more efficient compounds. Data available indicate that a better understanding of fabric construction as it applies to repellency, coupled with the now available water-repellent agents, will lead to some more nearly idealized type of water-repellent garment. In regard to testing methods, it is required that correlation is established between the Water-Repellent Fabrics results of laboratory test methods and performance of fabrics.

As already stated, the contact angle is influenced by the following factors: The’ chemical nature of the solid surface, the porosity of the surface, and the presence of other molecules on the surface. Again, any one or all of these factors could diminish the contact angle during wetting of the fabric. The change will indicate moisture regain of the sample which will show that the rate at which a fabric absorbs moisture increases the proportion to the number of times the sample has been wetted. It is of interest to re-exam the surface factors that might be responsible for the increase in moisture absorption.

The loss in the repellent agent, the change in position of the fibers in the yarns, and the creation of new surface could all affect the rate of water absorption. The swelling of partially coated or uncoated fibers would also result to make available more hydrophilic surfaces (OH groups). Now, a team at MIT has come up with a promising solution: a coating that not only adds water-repellency to natural fabrics such as cotton and silk but is also more effective than the existing coatings.

The new findings are described in the journal Advanced Functional Materials, in a paper by MIT professors Kripa Varanasi and Karen Gleason, former MIT postdoc Dan Soto, and two others.

Closing Remarks

Now that you know that “water-repellent” is a characteristic, and understand the differences between water-resistance and waterproofness in fabrics, you should have a newfound sense of reassured confidence when purchasing the perfect product that meets your needs. Being mindful of label descriptions can greatly assist you in deciding whether a product will be suitable for the conditions that you expose it to.