CRYSTAL MORPHOLOGY AND PHASE IDENTIFICATION IN POLY(ARYL-ETHER-KETONE)S AND THEIR COPOLYMERS .4. MORPHOLOGICAL OBSERVATIONS IN PEKK WITH ALL P-PHENYLENE LINKAGES

The thin film crystalline morphology of poly(aryl ether ketone ketone) having all p-phenylene linkages [PEEK(T)] has been investigated via t ransmission electron microscopy (TEM) and electron diffraction (ED) ex periments. PEKK(T) samples isothermally crystallized from both the mel t and the quenched glassy state over a temperature range of 160-360 de grees C have been examined, and two polymorphs (form I and form II) ha ve been found. At low supercoolings, micrometer-size faceted single la mellar crystals can be found either from the melt or from the glassy s tate for both forms I and II. On the basis of ED results obtained from the single lamellar crystals, the c-axis in both forms is not perpend icular to the substrate. This leads to different single crystal shapes observed experimentally. Chain folding along the a-axis is recognized on the basis of the evidence from polymer decoration and lamellar mic rodeformation experiments. With decreasing crystallization temperature , spherulitic texture becomes dominant and an edge-on type of narrow r ibbon-like lamellar orientation in the spherulites is increasingly dis torted. The morphology of PEKK(T) obtained via solvent-induced crystal lization by methylene chloride shows very small crystallites having a size less than 50 nm in three dimensions.