CRYSTALLIZATION BEHAVIOR OF POLY(ETHER ETHER KETONE KETONE)

The melting behavior of semicrystalline poly(ether ether ketone ketone ) (PEEKK) has been studied by differential scanning calorimetry (DSC). When PEEKK is annealed from the amorphous state, it usually shows two melting peaks. The upper melting peaks arise first, and the lower mel ting peaks are developed later. The upper melting peaks shown in the D SC thermogram are the combination (addition) of three parts: initial c rystal formed before scanning; reorganization; and melting-recrystalli zation of lower melting peaks in the DSC scanning period. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the isothermal crystallization; the Avrami constant, n, is about 2 for PEEKK from the melt and 1.5 for PEE KK from the glass state. According to the Lauritzen-Hoffman equation, the kinetic parameter of PEEKK from the melt is 851.5 K; the crystalli zation kinetic parameter of PEEKK is higher than that of PEEK, and sug gests the crystallizability of PEEKK is less than that of PEEK. The st udy of crystallization on PEEKK under nonisothermal conditions is also reported for cooling rates from 2.5 degrees C/min to 40 degrees C/min , and the nonisothermal condition was studied by Mandelkern analysis. The results show the nonisothermal crystallization is different from t he isothermal crystallization. (C) 1996 John Wiley & Sons, Inc.