2. Experimental
2.1. Materials
2.1.1. Keratin feather fiber
Keratin feather fiber is obtained from Featherfiber
Corporation (Nixa, MO). The keratin feather fiber is
cleaned and separated from the quill fraction according
to a process developed and patented by the USDA [33].
The feather fiber is semi-crystalline and has an average
diameter of 5 lm. Feather fiber has an experimentally
determined density of 0.89 g/cm3 [15]. Hong and Wool
[34] report a density value for hollow keratin fiber of
0.80 g/cm3 although the type of keratin fiber is not
known. Fiber lengths of 0.1 and 0.0053 cm are made
by grinding and sieving processes previously described
[15]. Average fiber lengths are found by imaging the
ground fiber in the scanning electron microscope
(SEM). The average fiber length found in SEM correlates
well with the predominant fraction obtained from
sieving and the predominant fraction is the one used
in the experiments.