Waterproof breathable fabrics by Vignesh Dhanabalan

Waterproof breathable fabrics: Technologies and practices March 14, 2014

Vignesh Dhanabalan (M.Tech) 1

“Waterproof breathable fabrics: Technologies and practices”

Authors: Vignesh Dhanabalan [1]

, Joshi Rashmi M [2]

. and Laga S.K [3]

D.K.T.E.S Textile & Engineering Institute, Ichalkaranji-416115(M.H), India

Email: [email protected]

Abstract

Textile and Apparel are sun-riser industries in India. It is also one of the oldest and

largest profits making industry. Textile contributes substantially to India economy by exporting

goods to various countries in the globe. For the textile industry, it is time to take stock of the

situation and aim at vertical integration or tie up with downstream manufacturers to realize

greater benefits of value addition and face the future with greater confidence. As the

globalization of textile industry becomes a reality, we need to develop strategies for survival and

growth.

Due to technological advances and globalization business of apparel textiles is saturated.

And it opens the market for technical textiles. Textiles with multiple functions are the need of the

hour; this has given a positive dimension and potential for the growth of water proof breathable

fabrics. In spite of several methods to produce the fabric, really it is a difficult task as well an

opportunity to produce quality products in this area. In near future India will be one of the leader

in this area.

In this paper, we have made an attempt to elaborate various techniques with benefits and

limitations to produce the quality product so that we can compete in the global market in spite of

byjentine competition

Keyword: Air permeability, Breathability, Ventile, Water proofness.

mailto:[email protected]



1. Introduction

The human body continuously generates heat by its metabolic process. The heat is dissipated

from the body by convection, radiation, evaporation and perspiration. The heat generated should

be maintained constantly within and outside the body. During rest, most surplus body heat is lost

by conduction and radiation, whereas during physical activity, the dominant means of losing

excess body heat is by evaporation of perspiration. If the temperature rises the sweating

mechanism gets activated and eliminates the heat in the form of heat waves and perspiration. The

fabrics protect the human body from external heat, wind, water, and many harmful agents, and at

the same time it also permits effective transmission of moist vapor from inside to outside

atmosphere. If the breathability is high enough to compensate the body heat then the requirement

of generating perspiration will be limited. The term breathability is usually confused with wind

penetration and wick ability of the material. The term ‘breathable’ implies that the fabric is

actively ventilated. This is not the case. Breathable fabrics passively allow water vapor to diffuse

through them yet still prevent the penetration of liquid water. Breathability is one such factor that

decides the designing of apparel wears and some specific technical products. The pores of

breathable fabrics are 20000 times smaller than a drop of liquid water, but 700 times larger than

a water molecule, thus they are too small to allow liquid water to pass through, but large enough

to allow the passage of molecules of water vapor. For a fire fighting operation, in racer suits and

other jobs were higher metabolic activities are carried the body perspires heavily and the fabric

should transmit good level of water vapor while protecting the body from external heat and

pressure. Water proof is another such property that retards the passage of water molecules

through the structures they are specifically used in technical products. The property of

waterproof and breathability can be termed as water repellent fabrics.

The market going the customer way, the comfort property has become the prime aspect.

The introduction of new waterproof breathable fabrics has greatly increased the range of choice

for consumers. Measurement of comfort is not possible when it comes to perspective views. The

breathability and waterproof feature has been and will remain as major factor in deciding the

comfort level of the apparel [1-5].



2.1 Principles of moisture vapor transfer

The Principles of moisture vapor transfer is governed by inter yarn/ inter fiber spaces. The

moisture in the vapor form transmit through textile material by

1. Diffusion of the water vapor through the air spaces between the fibers.

2. Absorption, transmition and desorption of the water vapor by the fibers.

3. Transmition of water vapor by forced convection.

Textiles made from absorbent fibres, such as natural fibres and regenerated fibres; water is

absorbed by hygroscopic fibres, transported through the swollen fibres, and evaporated from the

outer surface of the textile. For textiles made from synthetic fibres water is taken up into the

capillary spaces between fibres and yarns [3]

2.2 The barrier for vapor diffusion is

1. Evaporating fluid layer (mix of fluids)

2. Confirmed air layer ( between skin and the fabric layer)

3. Boundary air layer and

4. Ambient air layer

2.3 Water vapor/Moisture transport mechanism

The mechanism by which moisture is transported in textiles, by water vapor diffusion and

convection in void space within the textile structure and, the liquid water diffusion by wicking of

liquid in capillaries. Capillary action is determined by two fundamental properties of the

capillary [1,2]:

2.3.1 Capillary’s diameter and surface energy.

Smaller the diameter greater is the surface energy, greater the tendency of a liquid to

move up the capillary. In textile structures, the spaces between the fibres effectively form

capillaries. Hence, the narrower space between these fibres, the greater is the ability of the textile

to wick moisture.



Capillary pressure and capillary raise are determined using

P = 2γLV cos / Rc , L = ((Rcγ cos /2)* t1/2

P = capillary pressure L = liquid pressure

Rc – capillary radius t and - time and viscosity

Fig 1(a) and (b): Water vapor transportation through breathable fabric.

2.4 Factors affecting ventilation

During no contact (wind with moisture), the variation in the air gap thickness creates a

high pressure between the air gap thickness and the atmosphere. When wind speed increases the

touch period also increase because of high pressure created between the outer and inner

microclimate and causing higher ventilation. The effect of air motion, fabric thickness, clothing

aperture, fabric permeability and the swinging action of the fabric affects the ventilation factor

[3].

3.Moisture management through breathable fabrics

Highly hydrophilic polymers are totally unsuitable for permanent fabric coatings.

Hydrophilic materials are too sensitive to liquid water and, if used as water proof coatings, they

would either dissolve completely or become so heavily swollen by rain that they would suffer



severe flex or abrasion damage. Coatings of silicone rubbers and some blends of polyurethane

(PU) and acrylic results in the formulation of better water proof fabric.

Fig 2: Hydrophilic polymer mechanism

The density and the geometry of the fabric pores can be varied according to the woven

fabric structure that influences on the liquid flow pattern (both intrinsic and downstream).

Darcy’s law is used to describe

γSV – γSL = γ LV cos

SV- solid/ vapor, SL – solid/ liquid LV – Liquid/vapor

3 Properties requirement for breathable fabrics

The desirable properties of waterproof breathable fabrics are listed below [9].

• Optimum heat and moisture regulation (thermo-regularity effect)

• Absorption of surplus heat.

• Water proofness.

• Good air and water vapor permeability.

• Rapid moisture absorption and conveyance capacity.

• Rapid drying to prevent catching cold.

• No/Minimum water absorption of the layer of clothing just positioned to the skin.

• Dimensionally stable even when comes in contact to water

• Durable (tear, peel, abrasion resistance)

• Easy care/launderability

• Hydrostatic resistance

• Lightweight

• Soft and pleasant touch



5. Methods of producing waterproof breathable fabrics

Different methods involved to produce breathable fabric

Closely woven fabrics

Micro porous membranes and coatings

Hydrophilic membranes and coating

Combination of micro porous and hydrophilic membranes and coating

Smart breathable fabrics

Fig 3: Different layers of breathable fabric

5.1.1 Closely woven structure

Closely woven fabrics are constructed either from absorptive and hydrophilic yarns or

microfiber synthetic yarn which results in small size of pores to give maximum protection

against wind and rain. The surface area and concentration of inter yarn spaces should be as high

as possible to maximize water vapor transmission through woven fabrics and, the fabrics should

preferably be constructed from absorptive and hydrophilic yarns. The ability of the fibers to

undergo diffusion depends on the hydrophilic nature of the fibers, and then further liquid

transmission is assisted by capillary transfer within the fiber bundle. These fabrics initially are

not water proof, but as it comes in contact with water the cotton fibers swell to such an extent

that the inter yarn pores of the fabric are significantly reduced and there by restricting the

passage of water. The air permeability is also low, but the inter yarn spaces and hydrophilic

nature of the fiber allows adequate water vapor permeability. One of the famous waterproof

breathable fabrics “VENTILE” was manufactured by using long staple cotton with minimum

spaces between the fibres. Usually oxford weave is preferred to produce breathable fabrics.

When fabric surface is wetted by water the cotton fibres swell transversely reducing the size of



pores in the fabric and requiring very high pressure to cause penetration by reducing the pore

size to 3–4 µm. It can protect the water penetration for up to 20 minutes when the wearer is

submerged. Thus the swollen fabric in combination with the repellent finish provides excellent

protection against the wind, rain, seawater, and cold. The choice of the repellent treatment is

critical, it should allow absorption of water by substrate yarn to swell and constrict the inter-yarn

pores. Therefore waterproof is provided without the application of any water repellent finishing

treatment. Densely woven fabrics can also be produced from micro-denier synthetic filament

yarns. The individual filaments in these yarns are of less than 10 micron in diameter, so that

fabrics with very small pores can be engineered.

5.1.2 High-density woven (micro denier fiber)

Fabrics made using micro denier man-made filaments/fibers owe their breathability to the

densely woven, thin and smooth yarns that are usually made from microfibers. This type of

weaving results in a wind proof fabric with an excellent water vapor permeability compared with

laminates and coatings. Microfibers do not actually swell when wet. High density fabric made

out of microfilament yarn fabric exhibit very small pores.

5.2 Micro porous Membranes Coating and laminating

The coated and laminated breathable fabrics are either micro porous with hundreds of

open micro pores through which vapor passes or monolithic wherein the diffusion of vapor takes

place molecularly through hydrophilic hydrogen groups on the polymer chain through the solid

film or sometimes the combination of the two. The coating contains very fine inter connected

channels, much smaller than the finest raindrop but much larger than a water vapor molecule. In

Micro porous Membranes and Coatings the pore size ranges from 0.1 to 50 µm. PUs, poly-

tetrafluoroethylenes, acrylics, and polyamino acids are the most widely used coating elements.

Among these, PU is the most popular polymer because of toughness, flexibility of the film and

capability of tailor making the property of the film to suit the end use requirement. If the

maximum pore size at the outer surfaces of the barrier layer is about 2–3 µm or less, the

waterproof properties of the fabric are usually adequate. The micro porous structure is air-

permeable and is capable of transmitting water vapor at physiologically acceptable rates.



Fig 4: (a) and 3(b): pore size of coating material with water molecule’s size

In a moisture vapor permeable waterproof coated fabric, it comprising of a base fabric and a

synthetic microporous layer consisting of PU, the inner wall of each cavity is covered with a

water-repellent agent and at least part of the inner wall has a hole in it to communicate with

adjacent cavities. The microporous layer is formed from a coating solution of an organic solvent

containing PU elastomers. In case of micro porous membrane, holes are much smaller (2–3 µm)

than the smallest raindrops (100 µm), yet very much larger than a water vapor molecule (40 µm)

[5]. The micro porous films and coatings operate on similar principle, the water droplets cannot

penetrate the microspores of the film and coatings while the moisture vapor molecules are

pushed through. For a constant porosity and thickness, water vapor transmission through the

surface increases as the pore size decreases and as the fabric thickness increases water vapor

permeability decreases [1].

Various methods of generating micro porous membranes and coatings are as follows.

Mechanical fibrillation (only for membrane)

Wet coagulation process

Thermo coagulation (only for coating)

Foam coating (only for coating)

Solvent extraction

Radio frequency (RF)/ion/UV or E beam radiation

Melt blown/hot melt technology

Point bonding technology



5.2.1 Mechanical Fibrillation

Certain polymer films can be stretched in both directions and annealed to impart

microscopic rips and tears throughout the membrane. The best-known example is the

interconnecting pore structure of the very thin PTFE films

The microstructure of the uniaxial stretched film consists of nodes elongated at right

angles in the direction of the stretch. These nodes are interconnected by fibrils that are oriented

parallel to the direction of the stretch. Typically the size of the nodes varies from 50–400 µm.

The fibrils have widths of about 0.1 µm and lengths ranging from 5 to 500 µm. The development

of porosity occurs due to void formation between nodes and fibrils. When the films are biaxial

stretched, the fibril formation occurs in the other direction with the production of cobweb-like or

cross linked configurations with an increase in strength. Porosity increases as the voids between

the nodes and fibrils become more numerous and larger in size. The factors affecting the porosity

and strength of the film are as follows:

The crystallinity of polymer should be high, preferably > 98%.

Temperature and rate of stretching: higher temperature and higher rate of stretch leads to more

homogeneous structure with smaller closely spaced nodes, interconnected with a greater number

of fibrils, increasing the strength of the polymer matrix.

The temperature and duration of heat treatment: during heat treatment above the melting point of

the polymer, an increase in amorphous content of the polymer occurs. The amorphous region

reinforces the crystalline region enhancing the strength without substantially altering the

microstructure.

The expanded PTFE film contains a network of micro pores (82% by volume) of size

ranging from 0.1 to 50 µm and is claimed to have a density of 9 billion pores per square inch

[1,2]. In comparison to water molecules these pores are 20,000 times smaller, whereas 700 times

larger than that of water vapor molecules. Tetratec technology allows the pore size to be cast

from as little as 0.04–3.0 µm according to the customer’s engineered product requirements.

5.2.2 Wet Coagulation Process

This process produces a very fine interconnecting structure in which the micro pores are

small enough to keep droplets of water out but, large enough to let the small water vapor

molecules. Micro-porosity can also be created by leaching the salts on treatment of the film with



water. The coating obtained on wet coagulation shows ultrafine pores of < 1µm, in addition to a

honeycomb skin core structure of 1–20 µm pores. The formation of these micro pores was due to

the subtle difference in the rates of coagulation at the resin particle interface. Precise control over

the coating operation is required to generate a consistent, uniform pore structure, preferably

below 3 µm for optimum balance of breathability and water proofness.

5.2.3 Thermo Coagulation

The coating polymer can also be applied to the fabric from a mixture of a relatively

volatile solvent mixed with a proportion of a higher boiling nonsolvent. PU-based coating

technique operates on thermo-coagulation technique. PU is dissolved in a solvent mixture of

methyl ethyl ketone, toluene, and water, having 15–20% solids and coated on the fabric. The low

boiling solvent evaporates and leads to precipitation of PU in the nonsolvent.

5.2.4 Foam Coating

In this method, water based polyurethane/ polyacrylic acid esters are used. The foam is

stabilized with the aid of additives. Then the foam is coated on one side of the fabric. The coated

fabric is dried to form a micro porous coating. The fabric is finally calendared under low

pressure to compress the coatings. The foam cells being relatively large, a fluorocarbon (FC)

polymer based water-repellent finish is applied to improve the water resistant properties. The

water vapor permeability of foam-coated fabrics is higher and their water resistance was found to

be lower than those of non foam-coated fabrics with the same coating thickness. The water vapor

permeability and the water resistance become higher when the foaming speed is increased [1].

Polyurethane-based (PU) polymers have high flexibility even at low temperature because

of their low Tg. They also have good abrasion resistance and high resistance to chemicals and

water. As compared to PVC, PU coated fabrics form are soft and flexible without the aid of

plasticizers. In the absence of plasticizers the coated fabrics can withstand dry-cleaning and

washing.



Some applications of polyurethane coatings are

PU-based film designed (Permatex) by J.B. Broadley coated on fabrics offers a vapor

permeability of at least 70%.

Grabotter membrane (Grabo Ltd.) used in waterproof shoes is a PU-based film.

Micro porous PU film is being produced by Acordis (Tarka) is applied by a transfer

process from the release paper and it can be applied to almost any type of substrate

5.2.5 Solvent Extraction

In Solvent Extraction the polymer is dissolved in a water-miscible solvent and is coated directly

on to the fabric. The micro porous structure of the coating is developed by passing the coated

fabric through a coagulation bath where the solvent is displaced by water. Whereby, finely

divided water-soluble salts are incorporated into the coating formulation. The salt particles are

subsequently extracted from the dried and cured coating, by passing the fabric through a water

bath.

5.2.6 Radio Frequency/UV

In this process, various FC films are deposited by ion beam sputtering in the deposition

chamber. Sputtering of Teflon target was performed by an Ar ion beam with energy in the range

of 1.0–2.1 KeV with an ion current ranging from 20–35 mA. The moisture permeability of the

coated fabrics is similar to that of uncoated fabrics since only the fiber surface has been

individually covered with the coated grains while the fabric still remain original with numerous

pores. It was found that an increased target-substrate distance (TSD) led to a decrease in

deposition rate, while decreased TSD makes the coating more uneven. The contact angle of the

coated specimens obtained at higher energy was found to be smaller than that obtained at lower

energy for a given washing time.

5.2.7 Melt blown /hot melt technology

Breathable fabric produced with melt blown technology, may comprise at least one layer

of course, melt-spun, thermoplastic filaments and at least one layer of fine, melt-blown

thermoplastic microfibers. The layers are thermally bonded together at intermittent points.



Micro pores can become enlarged when garments are stretched at elbows and knees

affecting water proofing characteristics. On the other hand hydrophilic film and coatings do not

lose their properties on cleaning and stretching of garments. A hydrophilic film is sometimes

applied on microporous films to upgrade the water resistance.

Breathable coatings based on polyacrylamide (highly hydrophilic polymer) on cotton

fabrics have been developed. The coatings showed high water vapor permeability, while

providing desirable protection against air and liquid water-penetration.

5.2.8 Combination of Micro porous and Hydrophilic Membranes and Coatings

Fabrics coated with copolymers having both hydrophilic and hydrophobic segments. The

hydrophobic part provides water resistance and facilitates adherence of the coating to the

substrate, while hydrophilic part allow water vapor permeability. It offers solid layer like

properties of ‘wind-proofness’ and resistance to penetration by some solvents and light mineral

oils. It reduces stretch, which may cause opening of pores and possible water ingress through the

laminated product. But it adds to the stiffness of laminate, cost and reduces the breathability of

the fabric.

5.2.9 Smart breathable fabrics

The Shape memory polymer restricts the loss of body warmth by stopping the transfer of

vapor and heat at low temperature and at high temperature. It transfers more heat and water

vapor from inside clothing to outside than ordinary waterproof breathable fabrics. Shape memory

PU is one of the several shape memory polymers. At lower temperature the coating substance on

the fabric exists in a swollen state (by absorbing water from the surroundings) which results in

the closure of micro cracks. At a temperature higher than the transition temperature, the coating

exists in collapsed state (due to the predominance of Hydrophobic interactions) resulting in

opening of the micro cracks. Another factor which effects is the change in diffusion flux that is

governed by changes in both the diffusion coefficient and diffusion path of water molecules

through the swollen and collapsed coating. When a sudden change in ambient conditions occurs,

the PCM fabric delays the transient response and decreases body heat loss.



5.2.10 Polyurethane water breathable coating

Manjeet Jassal et al made studies on the Waterproof Breathable Polymeric Coatings

Based on Polyurethanes and stated that the water vapor permeability values were found to

increase with an increase in hydrophilic component while the water penetration resistance

increased with an increase in hydrophobic component. By varying the relative proportion of

hydrophilic and hydrophobic components, the WVP and water penetration resistance for

different end applications can be optimized [7].

Micro porous polyurethane coatings consist of an interconnected network of minute pores

usually produced by wet coagulation process. The pores are sufficient enough to allow individual

molecules of water vapor (0.0004 µm dia) to pass through the coating, whereas they do not

permit the passage of liquid water droplets (> 100 µm diameter) .

6. Method employed for application of coating

The lamination process has to be chosen carefully to ensure that the breathability of the

laminate is maintained at a high level.

There are four main methods of incorporating membranes into textile

Laminate of membrane and outer fabric

Liner or insert processing

Laminate of membrane and lining fabric

Laminate of outer fabric, membrane and lining

6.1 Laminating

Laminating waterproof breathable fabrics are made by application of membranes onto textile

product. They are thin membrane made from polymeric materials that offer high resistance to

water penetration but allow water vapor at the same time. The maximum pore size of the

membrane is around 10 micron. They are of two types:

1) Micro porous membranes 2) Hydrophilic membranes

Micro porous membranes have tiny holes on their surface smaller than a rain drops but

larger than water vapor molecule. Some of the membranes are made from Polytetrafluroethylene

(PTFE) polymer, Polyvinylidene fluoride (PVDF) etc,. The hydrophilic membranes are thin



films of chemically modified polyester or polyurethane. The poly (ethylene oxide) constitutes

hydrophilic part of the membrane by forming amorphous region in the main polymer system.

This amorphous region acts as intermolecular pores allowing water vapor molecules to pass

through but, preventing the penetration of liquid water due to the solid nature of the membrane.

Fig 4: Laminated waterproof breathable fabrics

7. Breathable, Permanent Water-Repellent Treatment of Cotton

Rudolph d. Deanin made etherification on cotton to determine Breathable permanent

Water-Repellent Treatment and stated that cotton fiber or fabric treated commercially with long

chain aliphatic acid chlorides in hot organic amine baths by a rapid economical process. To cause

low degrees of etherification and produce good water repellency and dry-cleaning resistance,

with no loss of vapor permeability was observed [8].

8. Nano web on water proof and breathability

Hae Wook Ahn et al studied and compared the waterproof and breathable properties of

clothing made from an electrospun nanoweb and conventional coating of PTFE, and have stated

results that, the Nano web laminate had a higher water vapor transmission rate but lower water

resistance than the polytetrafluroethylene laminate. The water penetration tests carried suggested

that water resistances are sufficient enough to prevent wetting by rain. The wearing test revealed

that Nano web laminated clothing provided more comfortable clothing-microclimate than

polytetrafluroethylene laminated clothing in normal warm environment. In the rainy test

conditions, no difference was observed between the polytetrafluroethylene and the Nano web

laminated clothing in any of the measured variables [9].



Roohollah Bagherzadeh studied Transport properties of multi-layer fabric based on

electro spun nanofibers mats as a breathable barrier textile material and found that Multi-layered

electro spun nanofibers mats equipped fabric (MENMEF) showed better performance in

windproof property better than Gortex fabric. Also, the water vapor permeability of MENMEF

was in a range of normal woven sport and work clothing. Comparisons of barrier properties of

MENMEF and conventionally PTFE coated materials showed that, the properties obtained by

conventional PTFE could be achieved by layered fabric systems with electro spun Nano fiber

mats [10].

9. Water Vapor Transport through Protective Textiles at Low Temperatures

Volkmar T. Bartels et al studied on water vapor transport at low temperatures and have

stated that the moisture accumulation in clothing are much better in breathable than in non

breathable garments (These differences are highly significant on a level of at least p > 0.995).

The ability to transport water vapor and the physiological function of breathable foul weather

protective clothing existed at subzero ambient temperatures down to -20°C [11].

10.1 Testing of waterproof breathable fabrics

The many methods employed to test the water vapor permeability of the fabric they are

S.no Methodology Standard Purpose

1 Sweating Guarded Hot

Plate Tests

(ISO 11092, ISO

1999, and ASTM

F 1868)

Measurement of thermal and water-vapor resistance

under steady-state conditions

2 Upright Cup Method ASTM E96 Water Vapor Transmission of Materials , permeability,

plastics (general), plastic sheet and film, sheet material 3 Inverted Cup Method ASTM E96

4 Desiccant Inverted Cup Test Method

E96 M-05

5 Dynamic Moisture Permeation Cell Test

ASTM F 2298 Standard Test Methods for Water Vapor Diffusion

Resistance and Air Flow Resistance of Clothing

Materials Using the Dynamic Moisture Permeation

6 Moisture vapor transmition

cell

Moisture vapor transmition behavior of fabric

7 Dynamic moisture permeable cell

Moisture transmition capability of cell

8 Holographic bench technique

Calculating mass flow



10.2 Waterproof Rating

Waterproof Rating

(mm) Resistance provided Withstand capabilities

0-5,000 mm No resistance to some resistance to moisture Light rain, dry snow, no pressure

6,000-10,000 mm Rainproof and waterproof under light pressure Light rain, average snow, light

pressure

11,000-15,000 mm

Rainproof and waterproof except under high

pressure

Moderate rain, average snow, light

pressure

16,000-20,000 mm Rainproof and waterproof under high pressure Heavy rain, wet snow, some

pressure

20,000 mm+

Rainproof and waterproof under very high

pressure

Heavy rain, wet snow, high

pressure

10.3 Calculation of permeability index

The permeability index was developed by woodcock

Im = Rt/(LR x Ret)

Where Rt - the total thermal resistance of the clothing plus surface air layer (m2 ºC/W).

Ret total evaporation resistance of the clothing plus the air layer (m2 kPa/W).

Rt/Ret – the ratio represents effective heat transmition.

LR (lewis relation) - the ratio of evaporative mass transfer coefficient.

10.4 Acceptance standard level worldwide for water repellent breathable fabrics

BS 7209 is a standard widely acceptable throughout the world for the water vapor

permeable index (WVPI). The good breathable fabric should have a minimum of 80% and lower

grade should have at least 50% WVPI.

10.5 The relative water vapor permeability (%) is govern by

Heat loss when the fabric is placed on the measuring head X 100

Heat loss from bare measuring head

The main requirements for WVPI are based on

Water vapor permeability index percentage.

Resistance to water penetration.

Cold cracking temperature.

Surface wetting (spray rating) after cleaning.

http://www.evo.com/shop/clothing/outerwear/waterproof_000-mm.aspx

http://www.evo.com/shop/clothing/outerwear/waterproof_000-10-000.aspx

http://www.evo.com/shop/clothing/outerwear/waterproof_11-000-15-2.aspx

http://www.evo.com/shop/clothing/outerwear/waterproof_16-000-20-3.aspx

http://www.evo.com/shop/clothing/outerwear/waterproof_20-000-mm-2.aspx



Similarly, for a typical breathable fabric the acceptable parameters should have

Water-vapor permeability (min 5000gm-2

for 24 hrs)

Water proofness min 130 cm (hydrostatic pressure)

Wind proofness less than 1.5 ml/cm2/second @ 1M bar

11 Labeling of a water proof fabric and the breathable characteristics

Manufacturers describe the waterproof breathability of fabrics using two numbers. The

first is in millimeters (mm) and is a measure of how waterproof a fabric is. In the case of a 10k or

10,000 mm fabric, if a square tube with inner dimensions of 1” x 1” over a piece of said fabric is

set, it will be filled with water to a height of 10,000 mm (32.8 feet) before water would begin to

leak through. The higher the number, the more waterproof the fabric. The second number is to

measure how breathable the fabric is, and it is normally expressed in terms of how many grams

(g) of water vapor can pass through a square meter (m2) of the fabric from the inside to the

outside in a 24 hour period. In the case of a 20k (20,000 g) fabric, this would be 20,000 grams.

Larger the number, higher the breathability of the fabric.

12. Application of breathable fabrics in end products

12.1 Mechanical Counter Pressure (MCP) Suit.

A skin-tight suit for high tech cloth exerts pressure over the rocketer's body to provide

pressure. Open pores in the suit actually allow the body to be cooled by perspiration. Tears will

cause bruising to the skin, but are not as lethal as they are on a conventional suit. These materials

provide 20% energy expenditure compared with NASA suit [13].

12.2 Air Permeable Outerwear

Gore tech, Polartec Neoshell and Mountain Hardwear Dry.Q allow a nominal amount of

airflow, helping to more quickly and effectively carry moisture away from your body.

Meanwhile, they remain totally water and windproof. You get breathability comparable to a soft

shell and waterproofing on par with a hard shell. You stay 100 percent dry from the inside and

out.

http://web.archive.org/web/*/http:/human.space.edu/old/docs/iacfull.pdf

http://en.wikipedia.org/wiki/Space_activity_suit

http://www.marssociety.org.au/marsskin.php

http://mvl.mit.edu/EVA/biosuit/index.html

http://www.polartec.com/shelter/polartec-neoshell/

http://www.mountainhardwear.com/DryQ/DryQ,default,pg.html



12.3 Neoprene sports wear

Stomatex “breathable neoprene” is made from closed-cell foam neoprene. These fabrics

can be applied as laminates or loose linings according to users’ requirements. The product is

suitable for use wherever thermal insulation or body protection is required and comfort would

normally be compromised by sweating. It has already been used in wide-ranging application

including orthomedical supports, sports supports, back supports, equestrian underwear, surface

water sports, wetsuits, survival suits, surfing wetsuits, warm-up suits, dive suits, liners and

footwear [15].

12.4 Mountain wear

Mountain Hardwear's Dry.Q water-proof breathable fabric is among a new breed of

sporting apparel [14]

Fig 5: Breathable snow protect mountain wear

12.5 Medical Fabric Waterproof and Breathable

Eastex Medical Fabrics include 100% polyester and polyester-nylon blends offered in

several stretch and non-stretch constructions with different coatings to match specific product

requirements. Fluid-proof, breathable, antimicrobial, flame-retardant, and air-tight for

manufacturing inflatable products, these healthcare fabrics can be sewn and sonic- or RF welded.

A full line of fabrics for OEMs and contract manufacturers of healthcare products such as

wheelchair cushions, mattresses, and orthopedic braces [18].



Neo-G MEDICAL GRADE OPEN PATELLA KNEE SUPPORT 'breathable design

Used For - strains, sprains and instability, injured, weak or arthritic knees, patellar

tracking, rehabilitation, sporting and occupational injuries

Fig 6: Neo-G knee support

12.7 3M™ Conformable Breathable Incise Tape 9948

The Conformable Incise Tape is a single coated medical tape consisting of a 1 mil moisture

vapor permeable plastic film coated with a hypoallergenic, pressure sensitive adhesive. They are

translucent material with very Good MVTR, high breathability and Comfortness.

Fig 7: 3M incise tape 9948



13. Conclusion

Thermal comfort remains a major comfort factor in deciding of the fabric. Thermal

comfort can be attained once when the difference in outer temperature is in parallel to the

microclimate created within the fabric. Various ventilation factors for the required end

application have to be predetermined clearly without fail because wrong usage leads to lag in

comfortness.

Extensive research is required to understand the relationship between segmental

ventilation and local comfort of the fabric subjected to active usage of the person.

14. Bibliography

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Waterproof Breathable Fabrics Part I, Fundamental Principles and Designing Aspects of

Breathable Fabrics, Journal of Industrial Textiles 2008 37: 225.

2. Apurba das and R.Alagiruswamy, science in clothing comfort, Woodhead publications,

ISBN 13:978-81-908001-5-0, 2010.

3. Shishoo.R, Textiles for Sport, Woodhead publications, ISBN 978-1-85573-922-2, 2005.

4. Williams.J.T, Textiles for cold weather apparel, wodhead publications, ISBN 978-1-

84569-411-1, 2009

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6. Shirley Institute, Toray Industries Inc., Naka, Y. and Kawakami, K. (1985).Moisture-

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Polymeric Coatings Based on Polyurethanes, Journal of Industrial Textiles 2004 33: 269

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Treatment of C1ot, Textile Research Journal 1970; 40; 970.

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Textiles at Low Temperatures, Textile Research Journal 2002 72: 899.

10. Holme, I., Porous Polymers and Fusible Films, J. Coated Fabrics 15, 198–204 (1985).



11. Hae Wook Ahn, Chung Hee Park and Seung Eun Chung, Waterproof and breathable

properties of nanoweb applied clothing, Textile Research Journal 81(14) 1438–1447.

12. Roohollah Bagherzadeh, Masoud Latifi, Saeed Shaikhzadeh Najar1, Mohammad Amani

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13. Sanjay S. Chaudhari, Rupali S. Chitnis and Dr. Rekha Ramkrishnan, Waterproof

Breathable Active Sports Wear Fabrics, 2010.

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ISBN 13:978-81-908001-5-0, 2010.

15. http://www.projectrho.com/public_html/rocket/spacesuits.php

16. http://www.gizmag.com/future-fabrics-hydrophobic-down-zero-loft-dryq/20742/

Data retrieved from online source on 9/9/2013.

Education

Waterproof breathable fabrics by Vignesh Dhanabalan