In this paper, conditions are described for the efficient
compounding and molding of a keratin feather fiber/
HDPE composite. The compounding study indicates
that the best compounding conditions for producing
keratin feather fiber/HDPE composites would be a compounding
temperature of about 205 C at 75 rpm in a
Brabender mixing head. Optimum compounding conditions
would maximize fiber/polymer interactions, minimize
fiber degradation, and minimize viscosity in the
melt state. Some embrittlement of the composite may
occur at long compounding times, i.e., greater than 10
min, especially as temperature is increased.
When molding compounds at 2.1 MPa, the stiffness
of the composites remains stable at 205 C up to 6
min. However, after 6 min of molding the stiffness decreases
and the sample color begins to darken. Sample quality deteriorates after about 2 min of molding time
at 200 C or greater resulting in a low yield point. Typical
injection molding applications take a fraction of this
time for small to reasonably sized parts, i.e., tens of seconds,
so it would be possible to effectively mold components
at typical times and temperatures for polyolefins
without significant material degradation.
Processing conditions are important so the intrinsic
properties of the biologically derived fiber can be maintained.
It is possible that keratin feather fiber has higher
properties than polyolefins so reinforced composites can
be obtained [19–22,31]. Keratin feather fiber has a lower
density than polyolefins, which would result in composites
of lower density [15,31,34]. In the present study, the
density of the 20 wt% composite, assuming no voids,
would be 0.94 g/cm3, which is lower than the density
of HDPE 7760. It is found that processing of the natural
fiber composite material can proceed at times and temperatures
encountered during processing of polyolefins.
This may make the feather fiber a good candidate for
the modification of the tensile properties of polyolefins
if suitable composite formulations and processing avenues
can be found.