Poly(aryl ether ketone ketone)s (PEKK) was a high-performance engineer
ing plastics, By means of Wide Angle X-ray Diffraction (WAXD) and Diff
erential Scanning Calorimetry (DSC) methods, PEKK samples crystallized
in solvent induction, from glass state and from melting state were st
udied, Crystal forms I and II for PEKK were found, The formation of cr
ystal form II was dependent on thermal history and solvent induction,
and this form II had melting point 10 degrees C or so lower than that
of form I crystallized from glass state, All PEKK samples had low melt
ing peaks which were relevant to the polarization of PEKK molecular ch
ain, while they had nothing to do with thermal history, The heat of fu
sion for PEKK low melting peaks accounted for,percentage of 2 to 10 or
so of the whole heat of fusion, And PEKK has its equilibrium melting
point of 409 degrees C.