Waterproof Breathable Fabric:
Waterproof breathable fabrics are one of the harsh weather
fabrics that protect the wearer without hampering their efficiency. Garments
made from such fabrics keep water from entering and wetting the body but allow
the passage of air and moisture. The passage of water vapor from the garment
makes it breathable and hence comfortable.
Methods of waterproof breathable fabric making:
High density woven having better in their breathability
compared to the densely woven, thin and smooth yarns that are usually called
microfibres.this type weaving gives an excellent wind proof with water vapour permeability.
The major advantage of this type of fabric is their grip. These are mostly used
in ski clothing where water vapor permeability, wind proof are required rather
than water impermeability
2. Coatings:
Some garments are made water resistant by coating the outer
surface with a layer of hydrophobic ("water hating") chemical or wax.
When water droplets fall onto the fabric they "bead" due to the
surface tension of the water, and roll off. The disadvantage of this method is
that the coating is not always durable, and can be damaged during repeated
washing and flexing.
Microporous coatings:
Foam made out of aquas polymer dispersion, it will be pressed after being
dried.
- Wet coagulation: The coagulated PUR polymer will be precipted with salts.
- Dry Coagulation: An emulsion containing solvent and non solvent will be applied to the textile. During the evaporation of the solvent, the polyurethane will be coagulated in the non solvent forming a microporous structure.
3. Laminates:
A more durable method is to use a waterproof breathable film
or "membrane", which lies inside the garment. Socks and gloves
incorporate a film in this way. It lies between the inner and outer textile
fabrics. The film is both waterproof and breathable, and will never wash away.
Microporous
membranes:
- Microporous fluorocarbon film.
- Microporous PUR film
- Photo polymerized polyacrylate film
Hydrophilic membranes:
- Hydrophilic groups built into the polymer chain bring the water vapour molecules through the film.
As discussed in the section “Methods of waterproof breathable fabric making,” a fabric can be coated or laminated to
obtain the desired properties. However, there are certain advantages to the use
of coatings over the use of lamination.
Lamination, both hydrophilic and
microporous, displays low adherence to the fabric surface as compared to
coatings. The hydrophilic films also have lower moisture transmission ability.
One other disadvantage of using the films is that they are more expensive and
require experience to obtain accurate control
over web tension. The waterproof breathable properties of the fabric can be
altered by changing the number of layers
of coating, thickness of the layer, and the type of coating. Coatings also
impart better handle and drapability to the fabric, compared to the
laminations.
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