Compounds and Composite Materials - PEEK Biomaterials - page 30

Figure 3.10 Spinal fusion cages made from PEEK-OPTIMA image contrast grades implanted in phantom. Photo
courtesy of Invibio.

compounds containing 4%, 6%, or 20% barium
sulfate, the implant developer can, therefore, tailor the
amount of radiopacity of the device to achieve an
optimized level of contrast. The radiographs shown in
Fig. 3.10 illustrate this for PEEK-OPTIMA polymer
spinal fusion cages that have been made with no
additive and 6% and 20% image contrast additive,
respectively, compared with a metallic cage.
Substantially, as a consequence of their shape,
powders do not enhance the tensile strength of polymer
materials compared with fiber reinforcements,
although there are physical changes to the base

polymer that occur as a result of their addition.
Tabl e 3 .2 compares the mechanical properties of
barium sulfate-filled PEEK with unfilled PEEK. It can
be seen that increasing the amount of filler actually
reduces the tensile strength of the material from 100
through 95 MPa, to 90 MPa with the highest filler
loading. This strength reduction is offset by the bene-
ficial gain in X-ray contrast, which, as has been illus-
trated, increases with increasing amounts of additive.
As an alternative method to adding radiopaque
powder, metallic wires (markers) may also be added
to PEEK (particularly to PEEK composites) to make

Table 3.2 Mechanical Properties of PEEK-OPTIMA Image Contrast Grades

PEEK-OPTIMA
Image Contrast Grade
(Low Radiopacity)

PEEK-OPTIMA
Image Contrast Grade
(High Radiopacity)

PEEK-OPTIMA
Unfilled Property Test Method Units

Tensile
strength

ISO 527 MPa 100 95 90

Tensile
elongation

ISO 527 % 20 20 15

Flexural
modulus

ISO 178 GPa 4 3.8 4.5

Flexural
strength

ISO 178 MPa 170 150 150

kJ/m 2 Notched Izod

impact

ISO 180 7.6 7 8

Specific
gravity

ISO 1183 g/cc 1.3 1.36 1.49