Waterproof breathable fabrics
Dr. Jimmy Lam
Institute of Textiles & Clothing
Learning Objectives
What are waterproof breathable fabrics
 Type of waterproof breathable fabrics
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– Densely woven fabrics
– Membrances
– coatings
Waterproof breathable fabrics
Definition
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Waterproof breathable fabrics are designed for use in
garments that protection from the weather, that is from
wind, rain and loss of body heat.
Waterproof fabric completely prevents the penetration and
absorption of liquid water, in contrast to water-repellent
fabric, which only delays the penetration of water.
Traditionally, waterproof fabric was made by coating (like
animal fat, wax, vegetable oils). Nowadays, uses
polyvinylchloride (PVC) polymer.
Coated fabrics are, however, considered to be more
uncomfortable to wear than water-repellent fabric, as they
are relatively stiff and do not allow the escape of
perspiration of vapour.
Waterproof breathable fabrics
Definition
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Water-repellent fabric is more comfortable to wear but its waterresistant properties are short lived.
The ideal fabric should be waterproofed (do not allow water get into
the fabric) and breathable (allow water vapour escape from skin).
Breathable fabrics allow water vapour (gas) to diffuse through
fabric and still prevent the water penetration of liquid water.
Production of water vapour by the skin is essential to maintenance
of body temperature. The normal body temp. is 37 C, and skin temp
is between 33 to 35 C.
During physical activity, the body provides cooling by producing
perspiration. If the water vapour cannot escape to the surrounding,
the relative humidity of the microclimate inside the clothing
increase and clothing becomes uncomfortable to wear.
Perspiration rates and activities
Perspiration rates and activities
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Table 12.1 shows the perspiration rates and activities from
sleeping to max work rate.
If the body is to remain at the physiologically required temp.
clothing has to permit the passage of water vapor from
perspiration rate as shown in Table 12.1.
The ability of fabric to allow water vapour to penetrate is
commonly known as breathability.
The waterproof breathable fabrics prevent the penetration of
liquid water from outside to inside the clothing.
It can, however, permits the penetration of water vapour
(gas) from inside the clothing to outside atmosphere.
How to make a waterproof and
breathable fabric
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We want to prevent water molecule (liquid) to get it the
fabric and allow water vapour (gas) to pass from skin
to fabric.
The size of water droplet (liquid) is 100 μm and the
water vapour (gas) is 0.0004 μm and we need to make
a fabric with porous space around 10 μm.
In this way, it allows water vapour to pass through
(from skin to fabric) and prevent water droplet to
penetrate (from outside to fabric).
Types of waterproof breathable fabric
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There are several methods which can be used
to obtain fabrics which are both breathable
and water proof. They are:
1. Densely woven fabrics
2. Membranes (Gore-tex fabric)
3. Coatings
Densely woven fabrics
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Probably the first effective waterproof breathable fabric
was developed in the 1940s for military purposes and is
known as Ventile.
Ventile fabric uses the finest cotton yarn, combed and
piled together. The yarn is woven using Oxford weave,
which is a plain weave with two threads acting together
in the warp.
When the fabric surface is wetted by water, the cotton
fibres swell reducing the size of the pores in the fabric
and requiring very high pressure to cause penetration.
The fabric is thus rendered waterproof without the need
for any water repellent finishing treatment.
Highly dense woven plain fabric
Ventile fabric in dry state
Ventile fabric in wet state, closely
packed by swelling of cotton fibres
Highly dense fabric
Results
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The use of very fine fibres and filaments and dense
construction (setts) results in fabrics with very small
pore size compared with conventional fabrics.
Typical pore size for waterproof fabric is about 10 μm
compared with 60 μm for conventional fabric.
Ventile fabric has a pore size of about 10 μm when dry
and 3-4 μm when wet.
Fabric made from micro-filaments is claimed to have
7000 filaments per cm.
Breathable fabric by monofilament
fibres
Membranes
Membranes are extremely thin films made from
polymeric material and engineered in such a
way that they have a very high resistance to
liquid water penetration, yet allow the passage
of water vapour.
 A typical membranes is only 10 μm thick and is
laminated to a conventional textile fabric to
provide the necessary mechanical strength.
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Microspores membranes
(Gore-Tex)
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The first and probably best known microporous
membrane, developed by Gore in 1976.
(http://www.gorefabric.com)
This is a thin film of polytetrafluoroethylene (PTFE)
polymer with 1.4 billion tiny holes per cm2.
These holes are much smaller than the raindrops (2-3
μm compared with 100 μm), yet very much larger than
water vapour molecule (0.0004 μm).
Membrane
Discussion
What is waterproof and breathable fabric?
 How to make such fabric in texile?
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