Air and water vapor transmission
Air permeability consistently decreased with increasing
thickness (Figure 7). It increased when samples were
elongated by 50%; increases of 2.37, 0.78, and
0.65 cfm were respectively shown by the 20, 40, and
60 mm thick samples. A greater increase of air permeability
was shown in the thinner samples, because of
less fiber stacking.
Water vapor transmissions of all samples increased
with increasing temperature (Table 2). Water vapor
permeability decreased with increasing thickness, with
greater differences being shown by stretched and fixed
samples than the original. At 10 and 15C, temperatures
below the transition temperature, water vapor
permeability increased more in the stretched and fixed
samples than in the original samples. At 30 and 40C,
the differences between the stretched sample and
original sample were irregular. This was because at
above the Ttrans the stretched and fixed nanoweb completely
recovered and a few large pores were created
between the stacked fibers during recovery. At above
the Ttrans, the stretched and fixed nanoweb returned to
its original shape.