Introduction:
Waterproof breathable fabrics are designed for use in garments that provide protection from the environmental factors like wind, rain and loss of body heat. Waterproof fabric completely prevents the penetration and absorption of liquid water.
Waterproof breathable fabrics are designed for use in garments that provide protection from the environmental factors like wind, rain and loss of body heat. Waterproof fabric completely prevents the penetration and absorption of liquid water.
Basically during physical activity the body gives off moisture
in the form of perspiration water vapour. If the water vapour produced
increases the relative humidity of the atmosphere inside the clothing will
cause increased thermal conductivity of the insulating air this leads to the
wearer to feel uncomfortable, so the atmospheric conditions and relative
humidity have a considerable effect on the water vapour permeability.
The escape of body generated moisture vapour affects comfort in two ways: First, evaporative cooling or loss of latent heat by the escape of moisture vapour is a major way in which body generated thermal energy is dissipated. Secondly, the failure of clothing to allow sufficient moisture vapour diffusion results in condensation of water on the skin surface. So for achieving the comfort, contribution by the dissipated moisture only 1/3 .the balance required for comfort also depends on the environmental ability in the case of producing water, wind proof fabrics the breathability is important to feel the wearer comfort.
The water vapour exchange and exchange rate
depending on the temperature and pressure of the air. Since the pressure
variation in the environment is small, temperature is the only factor to be considered.
Consequently, the moisture vapour will diffuse from the air at higher temperature
and lower humidity to the air at lower temperature by higher relative humidity.
The escape of body generated moisture vapour affects comfort in two ways: First, evaporative cooling or loss of latent heat by the escape of moisture vapour is a major way in which body generated thermal energy is dissipated. Secondly, the failure of clothing to allow sufficient moisture vapour diffusion results in condensation of water on the skin surface. So for achieving the comfort, contribution by the dissipated moisture only 1/3 .the balance required for comfort also depends on the environmental ability in the case of producing water, wind proof fabrics the breathability is important to feel the wearer comfort.
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| Breathable Fabric |
The required values of water vapour permeability are 2400
g/m2/24 hr.
Importance
of breathability:
Breathability is the ability of a textile construction to
allow water vapor to pass out from the body through it, but does not allow
liquid from the outside to pass into it. This property is expressed as “moisture vapor transmission rate” or MVTR. It is “The steady water vapor
flow in unit time through unit area of body, normal to specific parallel
surfaces, under specific conditions of temperature and humidity at each
surface”.
The value is expressed in number of grams per square meter over a given period of time. Protection is discussed in two different terms in today’s textile market. It can mean protecting the wearer from elements from the outside environment such as rain, blood or other liquids, virus, wind, and microbial attack. It can also mean protecting the outside environment from the human wearer in applications such as clean room apparel and surgical gowns. In the case of clean room apparel, the protection could be from particulate matter, such as skin, flaking onto the very sensitive electronics being worked on. In the case of surgical gowns, the protection is prevention of the contamination of the patient from microorganisms that could be released by the gown wearer. The importance of comfort and protection in today’s textiles cannot be argued even though one can debate how much breathability is necessary for a textile to be comfortable. Preventing.
The value is expressed in number of grams per square meter over a given period of time. Protection is discussed in two different terms in today’s textile market. It can mean protecting the wearer from elements from the outside environment such as rain, blood or other liquids, virus, wind, and microbial attack. It can also mean protecting the outside environment from the human wearer in applications such as clean room apparel and surgical gowns. In the case of clean room apparel, the protection could be from particulate matter, such as skin, flaking onto the very sensitive electronics being worked on. In the case of surgical gowns, the protection is prevention of the contamination of the patient from microorganisms that could be released by the gown wearer. The importance of comfort and protection in today’s textiles cannot be argued even though one can debate how much breathability is necessary for a textile to be comfortable. Preventing.
Water vapor produced by the body from escaping to the
outside interferes with the basic chemical principle of achieving equilibrium.
The challenge, then, is to create a film that is a barrier to liquids yet
remains permeable to water vapor so that the fabric can relatively quickly
reach equilibrium between the inside and the outside. Meeting this objective
produces a textile construction that achieves the goals of protection and
comfort.
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