الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
One of the basic properties of the fibrous materials is their porosity. Porosity is
considered to be one of the basic features representing a textile structure. Porosity and air
permeability are vital properties in some applications such as filtration, thermal insulation,
fluid barriers, performance of parachute and sailcloth, transportation of the moisture from
body to environment, apparel comfort, thermal insulation properties, the rate of liquid
penetration during wet processing and liquid removal during drying of fabrics, etc.
In the industry of air filtration, air flow rate is the major important parameter in order
to design air filter. Air flow rate is a measure of the amount of air that flows through a filter. It
is related to the size of pores, differential pressure, total porosity, and filtration area. So,
measurement of porosity, air permeability and pore size are very important in the
development of filtration industry.
This work presents a simplified mechanism for the design and fabrication of porosity
test apparatus to determine the porosity of different textile structures. The test apparatus has
been manufactured and installed in the department of Textile Engineering Faculty of
Engineering, Alexandria University. After installation of the apparatus, the porosity tests of
the various textile structures have been performed. The effect of the different textile structures
parameters on their porosity was studied.
For the woven fabric, Increase the number of intersection result in decrease the air
permeability. So, the structure has the major effect on both permeability and porosity. Using
micro fiber layers with woven fabric, results in decreasing both air permeability and porosity.
For multi layer structure, the effect of the number of intersections on the air permeability will
decrease and disappear as number of layers increases. This phenomenon was successfully
used in the field of air filter design. Woven fabric can be used as a barrier for large solid
particles, this layer of woven fabric has no effect on the permeability of the filtration medium
but affects on the designed bursting pressure.
For nonwoven, porosity increases as air permeability increases (non-linearj.The lower
is the density, the higher is the porosity. Pore size affects the porosity more than the air
permeability. Porosity depends mainly on the pores area, but air permeability depends not
only on the pore size but also on the type of pores. Nonwoven weight affects air permeability
more than porosity.
Multi-layer nonwoven structures introduce pore size less than the smallest one of any
layer. So, choice of layers of a filtration medium depends on the specifications of each layer
like porosity, air permeability and pore size. In order to design air filter has the following
specification: porosity 75 %, air permeability 700 (Um2.s) pore size 77 micro meters, two
layers having a certain specification were chosen. The first layer specifications were porosity
80 %, air permeability 1400 (Um2.s) pore size 97 micro meters. The second layer
specifications were porosity 90 %, air permeability 3500 (Llm2.s) pore size 118 micro meters.
The resulting structure has approximately the same specification of the original filtration
medium.