Dynamic relaxation behavior of solvent‐crystallized poly(ether ether ketone)

The dynamic relaxation behavior of solvent‐crystallized poly(ether ether ketone) (PEEK) has been investigated in the region of the glass‐rubber (α) relaxation using dynamic mechanical and dielectric methods. Amorphous PEEK films were exposed to saturated methylene chloride and acetone vapor, with solvent‐induced crystallization observed for both penetrants. Sample desorption at elevated temperatures (under vacuum) resulted in virtually complete removal of residual penetrant, thus providing for the measurement of relaxation characteristics independent of plasticization. Both dynamic mechanical and dielectric studies indicated a marked positive offset in the isochronal relaxation temperatures of the solvent‐crystallized samples relative to thermally crystallized specimens of comparable bulk crystallinity, and a higher apparent activation energy in the solvent‐crystallized case. These results are consistent with the evolution of a tighter crystalline morphology (i.e., smaller crystal long spacing) in the solvent‐crystallized samples, the crystallites imposing a greater degree of constraint on the long‐range motions of the amorphous chains inherent to the glass‐rubber relaxation. © 1994 John Wiley & Sons, Inc.