TRANSPARENCY ENHANCEMENT IN SEMICRYSTALLINE PEEK THROUGH VARIATION OFPOLYMER MORPHOLOGY

We report a processing window in which transparent semicrystalline pol y(ether ether ketone) (PEEK) can be produced. The transparent PEEK fil m reported is 100 mu m in thickness and has light transmittance of 54% ; while ordinary semicrystalline PEEK him of the same thickness and de gree of crystallinity, but produced outside the processing window, is virtually opaque (with the light transmittance close to 0%). First pro cessing conditions for producing the transparent PEEK film are discuss ed, and second characterization of the transparent PEEK film is detail ed. Results suggest that the main processing condition for developing the transparent PEEK film is forming temperature, defined as the highe st temperature that the film is exposed to during thermal treatment. U sing transmission electron microscopy (TEM), differential scanning cal orimetry (DSC), and small-angle x-ray scattering (SAXS), we characteri zed morphology of the PEEK films. TEM shows that the morphology in the transparent PEEK film has a locally oriented lamellar structure, inst ead of the commonly observed spherulites or sheaves. DSC results sugge st that the new morphology is formed in the melt with a high density o f residual crystals that act as nucleating agents during the crystalli zation process, which is known as a self-seeding effect. SAXS spectra show that specimens with higher forming temperature produce broader di ffraction peak at larger Q value that is defined as 4 pi sin theta/lam bda. We conclude from the study that the light transmittance enhanceme nt is morphology related, and can be achieved through control of proce ssing conditions. (C) 1996 John Wiley & Sons, Inc.