Solvent-induced crystallization in poly(aryl ether ether ketone)

Sorption of CH2Cl2 (I) and I n-heptane liq. solns. in PEEK are analyzed and interpreted assuming multiple transport mechanisms. The presence of the highly interacting I is responsible for anomalous sorption behaviors. The sorption behavior of PEEK films immersed in I poor n-heptane solns. can be described by non-ideal Fickian diffusion, while limiting Case II and diffusion controlled swelling accompany equilibration in progressively richer I solns. The optical microscopy observation of cryogenically fractured samples conditioned in pure liq. I at 5, 20 and 36° for different times, revealed the presence of a sharp moving front. DSC indicates that the glass transition temp. of the penetrated shells was always lower than the treatment temp. The high levels of solvent swelling and plasticization were probably responsible for the crystallinity detected in DSC thermograms and wide-angle x-ray scattering (WAXS) diffractograms of the solvent treated and initially amorphous samples. The differences of WAXS diffractograms of samples crystd. by immersion in I at 5 and 36° for various times and by thermal treatment are discussed. Increasing levels of crystallinity were induced in the samples equilibrated in progressively richer I solns.