CRYSTALLIZATION BEHAVIOR OF POLY(ETHER ETHER KETONE) POLY(ETHER SULFONE) BLOCK-COPOLYMER/

The crystallization and melting behaviours of a multiblock copolymer c omprising poly(ether ether ketone) (PEEK) and poly(ether sulfone) (PES ) blocks whose number average molecular weights <((M)over bar (n)'s)> were 10 000 and 2900, respectively, were studied. The effect of therma l history on crystallization was investigated by wide-angle X-ray diff raction measurement. A differential scanning calorimeter was used to d etect the thermal transitions and to monitor the energy evolved during the isothermal crystallization process from the melt. The results sug gest that the crystallization of the copolymer becomes more difficult as compared with that of pure PEEK. The equilibrium melting point of t he copolymer was found to be 357 degrees C, about 30 degrees C lower t han that of pure PEEK. During the isothermal crystallization, relative crystallinity increased with crystallization time, following an Avram i equation with exponent n approximate to 2. The fold surface free ene rgy for the copolymer crystallized from the melt was calculated to be 73 erg cm(-2), about 24 erg cm(-2) higher than that of pure PEEK. Copy right (C) 1996 Elsevier Science Ltd.