Biomedical Engineering Reference
In-Depth Information
O
O
F
C
F
+
K
O
C
O
K
Sulfolane
O
*
O
C
*
Scheme 2.4
O
F
C
F
HO
OH
+
Diphenylsulfone
K
2
CO
3
O
*
O
O
C
*
Scheme 2.5
used in the synthesis of PAEK polymers
[3]
. The
inherent instability of bisphenates to oxidation was
overcome by the use of hydroquinone and sodium or
potassium carbonate to form the bisphenate in situ.
Very high temperatures (
>
300
C) are required
to reach high molecular masses, the molecular
weight being controlled by a slight excess of di-
fluorobenzophenone, leading to fluorine-terminated
chains (
Scheme 2.5
).
This process was patented in 1977 by ICI and sold
under the brand “Victrex PEEK,” and this route
provided the majority of PEEK polymer used in
industrial applications.
The establishment of the nucleophilic route to
PAEK polymers permitted the investigation of
polymer variants by the use of different bisphenols to
produce PAEK polymers with various properties, as
reported by Attwood et al.
[1]
. The family of PAEK
polymers grew to contain variants such as PEK,
PEEK, PEKK, PEKEKK, and so on, with a range of
glass transition temperatures (143
e
160
C) and high
crystalline melt temperatures (335
e
441
C). As the
dominant member of the PAEK family of polymers,
PEEK is in its “glassy” state at room temperature, as
its glass transition temperature occurs about 143
C,
whereas the crystalline melt transition temperature
(
T
m
) occurs around 343
C.
2.3 Nomenclature
The literature on PAEK resin is a maze of trade
names and producers, which have changed over the
years, complicating interpretation of reported data
for today's materials. For researchers interested in
deciphering the historical polymer science literature,
we provide here a brief primer on the nomenclature
of PAEK resins used for industrial purposes as well
as for biomaterials (
Table 2.1
). Resin, when used in
this context, refers to the neat, unfilled powder that is
created by polymerization, whereas grades are typi-
cally characterized by flow characteristics (e.g., for
injection molding or compression molding) or based
on their filler content (e.g., glass fiber or carbon
fiber). Because PAEK polymers are converted using
standard thermoplastic processing techniques, such
as injection molding, they are generally available as
pellets, although powder resin is also available. Stock
shapes,
such as
rods, are also available from
producers.
