INTRODUCTION
Ø Basically during physical
activity the body gives off moisture in the
form of perspiration water vapour
Ø 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.
Ø Secondly,the failure of
clothing to allow sufficient moisture vapour diffusion
results in condensation of water on the skin
surface
Ø Balance required for comfort
also depends on the environmental ability ,
in the case of producing water proof
fabrics the breathability is important
to feel the wearer comfort
Ø The required values of Water vapour
permeability are 2400 g/m2/24 hr.
Ø Water impermeability is 150 cm hydrostatic
head .
History in the development of waterproof breathable
fabric
Ø First the waterproof breathable fabric were developed by ministry
of defence,
United kingdom in 1940s to prevent the ship workers from the
sever
conditions
of the north atlantic ocean
Ø They used densely woven 100% cotton fabrics
called ventile.
Ø The most significant development was the
microporous membrane by
GoreTex in 1976 .
Ø It is a thin film of PTFE having a network of
small pores ( 1.4 billion per cm2 ).
Ø Latest developed coatings are non porous
hydrophilic polyurethane .
Importance of breathability
Ø 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
Ø This property is expressed as “moisture vapor
transmission rate” or MVTR .
Ø To achive
comfort to the wearer in the situations like rain, wind proof,
Breathability
of fabric is important.
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