Waterproof breathable fabricsWaterproof breathable fabrics

Dr. Jimmy LamDr. Jimmy Lam

Institute of Textiles & ClothingInstitute of Textiles & Clothing

Learning ObjectivesLearning Objectives

What are waterproof breathable fabricsWhat are waterproof breathable fabrics Type of waterproof breathable fabricsType of waterproof breathable fabrics

– Densely woven fabricsDensely woven fabrics– MembrancesMembrances– coatingscoatings

Waterproof breathable fabricsWaterproof breathable fabricsDefinitionDefinition

Waterproof breathable fabrics are designed for use in garments Waterproof breathable fabrics are designed for use in garments that protection from the weather, that is from wind, rain and loss that protection from the weather, that is from wind, rain and loss of body heat.of body heat.

Waterproof fabric completely prevents the penetration and Waterproof fabric completely prevents the penetration and absorption of liquid water, in contrast to water-repellent fabric, absorption of liquid water, in contrast to water-repellent fabric, which only delays the penetration of water.which only delays the penetration of water.

Traditionally, waterproof fabric was made by coating (like animal Traditionally, waterproof fabric was made by coating (like animal fat, wax, vegetable oils). Nowadays, uses polyvinylchloride fat, wax, vegetable oils). Nowadays, uses polyvinylchloride (PVC) polymer.(PVC) polymer.

Coated fabrics are, however, considered to be more Coated fabrics are, however, considered to be more uncomfortable to wear than water-repellent fabric, as they are uncomfortable to wear than water-repellent fabric, as they are relatively stiff and do not allow the escape of perspiration of relatively stiff and do not allow the escape of perspiration of vapour. vapour.

Waterproof breathable fabricsWaterproof breathable fabricsDefinitionDefinition

Water-repellent fabric is more comfortable to wear but its water-Water-repellent fabric is more comfortable to wear but its water-resistant properties are short lived.resistant properties are short lived.

The ideal fabric should be waterproofed (do not allow water get into The ideal fabric should be waterproofed (do not allow water get into the fabric) and breathable (allow water vapour escape from skin).the fabric) and breathable (allow water vapour escape from skin).

Breathable fabrics allow water vapour (gas) to diffuse through Breathable fabrics allow water vapour (gas) to diffuse through fabric and still prevent the water penetration of liquid water.fabric and still prevent the water penetration of liquid water.

Production of water vapour by the skin is essential to maintenance Production of water vapour by the skin is essential to maintenance of body temperature. The normal body temp. is 37 C, and skin temp of body temperature. The normal body temp. is 37 C, and skin temp is between 33 to 35 C.is between 33 to 35 C.

During physical activity, the body provides cooling by producing During physical activity, the body provides cooling by producing perspiration. If the water vapour cannot escape to the surrounding, perspiration. If the water vapour cannot escape to the surrounding, the relative humidity of the microclimate inside the clothing the relative humidity of the microclimate inside the clothing increase and clothing becomes uncomfortable to wear.increase and clothing becomes uncomfortable to wear.

Perspiration rates and activitiesPerspiration rates and activities

Perspiration rates and activitiesPerspiration rates and activities Table 12.1 shows the perspiration rates and activities from Table 12.1 shows the perspiration rates and activities from

sleeping to max work rate.sleeping to max work rate. If the body is to remain at the physiologically required If the body is to remain at the physiologically required

temp. clothing has to permit the passage of water vapor temp. clothing has to permit the passage of water vapor from perspiration rate as shown in Table 12.1.from perspiration rate as shown in Table 12.1.

The ability of fabric to allow water vapour to penetrate is The ability of fabric to allow water vapour to penetrate is commonly known as breathability.commonly known as breathability.

The waterproof breathable fabrics prevent the penetration of The waterproof breathable fabrics prevent the penetration of liquid water from outside to inside the clothing.liquid water from outside to inside the clothing.

It can, however, permits the penetration of water vapour It can, however, permits the penetration of water vapour (gas) from inside the clothing to outside atmosphere.(gas) from inside the clothing to outside atmosphere.

How to make a waterproof and How to make a waterproof and breathable fabricbreathable fabric

We want to prevent water molecule (liquid) to get it We want to prevent water molecule (liquid) to get it the fabric and allow water vapour (gas) to pass from the fabric and allow water vapour (gas) to pass from skin to fabric.skin to fabric.

The size of water droplet (liquid) is 100 The size of water droplet (liquid) is 100 μμm and the m and the water vapour (gas) is 0.0004 water vapour (gas) is 0.0004 μμm and we need to make m and we need to make a fabric with porous space around 10 a fabric with porous space around 10 μμm.m.

In this way, it allows water vapour to pass through In this way, it allows water vapour to pass through (from skin to fabric) and prevent water droplet to (from skin to fabric) and prevent water droplet to penetrate (from outside to fabric).penetrate (from outside to fabric).

Types of waterproof breathable fabricTypes of waterproof breathable fabric

There are several methods which can be used There are several methods which can be used to obtain fabrics which are both breathable to obtain fabrics which are both breathable and water proof. They are:and water proof. They are:

1.1. Densely woven fabricsDensely woven fabrics

2.2. Membranes (Gore-tex fabric)Membranes (Gore-tex fabric)

3.3. CoatingsCoatings

Densely woven fabricsDensely woven fabrics Probably the first effective waterproof breathable fabric Probably the first effective waterproof breathable fabric

was developed in the 1940s for military purposes and is was developed in the 1940s for military purposes and is known as Ventile.known as Ventile.

Ventile fabric uses the finest cotton yarn, combed and Ventile fabric uses the finest cotton yarn, combed and piled together. The yarn is woven using Oxford weave, piled together. The yarn is woven using Oxford weave, which is a plain weave with two threads acting together which is a plain weave with two threads acting together in the warp.in the warp.

When the fabric surface is wetted by water, the cotton When the fabric surface is wetted by water, the cotton fibres swell reducing the size of the pores in the fabric fibres swell reducing the size of the pores in the fabric and requiring very high pressure to cause penetration.and requiring very high pressure to cause penetration.

The fabric is thus rendered waterproof without the need The fabric is thus rendered waterproof without the need for any water repellent finishing treatment.for any water repellent finishing treatment.

Highly dense woven plain fabricHighly dense woven plain fabric

Ventile fabric in dry state

Ventile fabric in wet state, closely packed by swelling of cotton fibres

Highly dense fabricHighly dense fabricResultsResults

The use of very fine fibres and filaments and dense The use of very fine fibres and filaments and dense construction (setts) results in fabrics with very small construction (setts) results in fabrics with very small pore size compared with conventional fabrics. pore size compared with conventional fabrics.

Typical pore size for waterproof fabric is about 10 Typical pore size for waterproof fabric is about 10 μμm m compared with 60 compared with 60 μμm for conventional fabric.m for conventional fabric.

Ventile fabric has a pore size of about 10 Ventile fabric has a pore size of about 10 μμm when dry m when dry and 3-4 and 3-4 μμm when wet.m when wet.

Fabric made from micro-filaments is claimed to have Fabric made from micro-filaments is claimed to have 7000 filaments per cm. 7000 filaments per cm.

Breathable fabric by monofilament Breathable fabric by monofilament fibresfibres

MembranesMembranes

Membranes are extremely thin films made from Membranes are extremely thin films made from polymeric material and engineered in such a polymeric material and engineered in such a way that they have a very high resistance to way that they have a very high resistance to liquid water penetration, yet allow the passage liquid water penetration, yet allow the passage of water vapour.of water vapour.

A typical membranes is only 10 A typical membranes is only 10 μμm thick and is m thick and is laminated to a conventional textile fabric to laminated to a conventional textile fabric to provide the necessary mechanical strength.provide the necessary mechanical strength.

Microspores membranesMicrospores membranes(Gore-Tex)(Gore-Tex)

The first and probably best known microporous The first and probably best known microporous membrane, developed by Gore in 1976. (membrane, developed by Gore in 1976. (http://www.gorefabric.comhttp://www.gorefabric.com))

This is a thin film of polytetrafluoroethylene (PTFE) This is a thin film of polytetrafluoroethylene (PTFE) polymer with 1.4 billion tiny holes per cmpolymer with 1.4 billion tiny holes per cm22..

These holes are much smaller than the raindrops (2-3 These holes are much smaller than the raindrops (2-3 μμm compared with 100 m compared with 100 μμm), yet very much larger than m), yet very much larger than water vapour molecule (0.0004 water vapour molecule (0.0004 μμm).m).

MembraneMembrane

DiscussionDiscussion

What is waterproof and breathable fabric?What is waterproof and breathable fabric? How to make such fabric in texile?How to make such fabric in texile?