Yc. Ke et Zw. Wu, INVESTIGATIONS OF THE PRACTICAL ROUTES, STRUCTURE, AND PROPERTIES FORPOLY(ARYL ETHER KETONE KETONE) POLYMERS, Journal of applied polymer science, 67(4), 1998, pp. 659-677
Different routes for preparing poly(aryl ether ketone)s (PEKKs) are pr
esented and compared. The properties of PEKKs are related to the conte
nt of metaphenyl links in the molecular main chains, the molecular cha
in branching degree, the gelation content by molecular crosslinks, and
, especially, the relative content of crystal form II to crystal form
I of the PEKK polymorphism. When the molecular T/I ratio of 50/50 in t
he polymer chains is reached, the obtained PEKK has a lower melting po
int and gelation content (2% or so). The PEKKs prepared from the elect
ronical substitution route (E route) often have a 0-30% content of cry
stal form II (relative to the mixed form I and form II), which is much
more than that in PEKKs from the nucleophilic substitution route (N r
oute, form II accounts for 0-20%). The relatively unstable crystal for
m II resulted in the unstable and difficultly predicted thermal proper
ties of PEKKs. PEKKs from different routes provide samples with meltin
g points from 360 to 397 degrees C (T-m) and glassy transition tempera
tures (T-g) from 167 to 176 degrees C and the equilibrium melting poin
t of 411 degrees C for para-PEKK, while the tensile strength of the ho
mopolymer PEKK and copolymers of PEEKK (poly(aryl ether ether ketone k
etone)-PEKK can reach 100 MPa prepared by the N route. The high T-g ma
kes PEKK polymers practically useful while too high T-m and a very sma
ll difference between T-m and T-d (degradation temperature) produce ob
stacles to its wide application. The reaction mechanisms of both elect
rophilic and nucleophilic routes are investigated and discussed in det
ail. Results show that the molecular chain branched by solvents and mo
nomers with many activated points may be partly reduced to some extent
by the oligomer and extruding route. (C) 1998 John Wiley & Sons, Inc.