Biomedical Engineering Reference
In-Depth Information
Figure 3.20
Chopped carbon fibers (6 mm) prior to compounding with PEEK polymer in a twin-screw extruder. Photo
courtesy of Invibio.
a specific format to enable them properly to feed
through the loss-in-weight feeder and the design of
the screw profile to achieve good mixing, while
achieving a good fiber length distribution is also very
important. With powders there is a requirement not to
cause them to agglomerate at any stage of the process
and to achieve good dispersion. Weighing and
packaging the final compounded products are the
final stages before samples are tested for batch
approval.
3.4.2 Continuous CFR PEEK
Continuous fiber-reinforced materials cannot be
manufactured using conventional polymer process-
ing equipment such as compounding extruders
described earlier. The long fibers and high fiber
loading (usually around 60
e
65% by volume)
preclude any type of screw-based processing equip-
ment in the conventional sense. Instead, continuous
carbon fiber-reinforced materials have to be
produced by a process in which the carbon fibers and
polymer are combined with minimal amounts of
shear, because this would disrupt the fibers and lead
to significant fiber breakage. In essence, in the case of
continuous reinforcement, the polymer is melted and
Figure 3.21
Chopped compounded pellets (30% by
weight short carbon fiber-filled PEEK-OPTIMA). Photo
courtesy of Invibio.
Figure 3.22
Compounding room for short carbon fiber-
reinforced PEEK-OPTIMA. Photo courtesy of Invibio.
