Crystallization and morphology of poly(aryl-ether-ether-ketone)

Abstract

The morphology of poly(aryl-ether-ether-ketone) (PEEK) has been studied using optical microscopy (at room temperature and at elevated temperatures), small-angle light scattering (H v and V v ), transmission electron microscopy (bright field, dark field, and selected area electron diffraction), and wide and small-angle X-ray scattering. As expected, density of nucleation and hence spherulite size depends on melt temperature. Higher melt temperatures give rise to low nucleation density and hence large spherulites. The spherulite growth rate is independent of melt temperature and depends on crystallization temperature. The sign of the spherulite birefringence was determined between room temperature and 320°C by polarizing microscopy and at room temperature by V v light scattering. In this temperature range the spherulites were negatively birefringent. From selected area electron diffraction, the crystal unit cell b-axis is found to align along the radius of the spherulite. The crystallographic (110) plane, which makes an angle of 52.7 degrees with the radial b-axis, appears to be the preferred growth plane. Chain polarizability was also calculated using refined atomic coordinates and the bond polarizabilities. PEEK crystals were more stable in the electron beam, by about an order of magnitude, than polyethylene.