Melting and morphology in melt-crystallized meta-linked poly(aryl ether ketone)

Unique thermal behavior and accompanying morphology in meta-linked poly(eth er diphenyl ether ketone) (PEDEKm) melt-crystallized at various conditions was analyzed. The two widely spaced and well-resolved melting peaks (T-m,T- 1 and T-m,T-2) in PEDEKm offered a unique model for proposing a more advanc ed interpretation on the complex and highly controversial issues of multipl e melting and crystalline morphology commonly seen in semi-crystalline poly mers. There are two main lamella types of different thickness populations, whose melting peaks labeled P1 and P2 may appear in series giving two melti ng endotherms at 302 and 322 degreesC, respectively. However, despite the s eries appearance of two melting peaks upon scanning, only one type of lamel lae preferentially exists in the melt-crystallized PEDEKm depending on proc essing temperatures/histories. When isothermally crystallized at lower temp eratures (290 degreesC or lower), PEDEKm possesses only the P1 crystal, whi ch may or may not be melted/re-crystallized into thicker P2 crystal entity depending on heating rates or annealing temperature/time. A break-off tempe rature fur lamellar thickness in PEDEKm is about 300 degreesC. When crystal lized at 300 degreesC or higher, PEDEK developed only the P2 crystal, which is mainly a thickened and branched axialite. This study also demonstrated that the unit cell remained unchanged for either the P1 or P2 crystal entit ies. (C) 2001 Published by Elsevier Science Ltd.