CRYSTAL-STRUCTURE AND ITS TRANSITION FOR POLY(ARYL ETHER KETONE KETONE)S .1.

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.