On the observation of a new morphology in poly(arylene ether ether ketone). A further examination of the double endothermic behavior of poly(arylene ether ether ketone)

Abstract

The morphology of solvent-cast or melt-pressed isothermally crystallized poly(ether ether ketone) (PEEK) films was investigated by polarized optical microscropy as a function of crystallization temperature. For crystallization temperatures below 300 °C, only spherulitic morphologies were present whereas, at higher temperatures, a morphological transition from spherulitic to crystal-aggregate-like structures could be observed during isothermal crystallization. As the crystallization temperature is increased, the content in the second type of structures was observed to increase. The temperature dependence of the relative population in these two morphologies can be qualitatively correlated with that of the double endothermic behavior observed when PEEK is heated above its crystallization temperature. The observation of this new morphology for PEEK cannot be explained in terms of a polymorphic behavior, a degradation process, or a fractionation effect during crystallization. At this point we can only speculate that it may be related to the structure of the amorphous liquid phase from which the crystallinity develops.

Mechanisms of reorganization of lamellae in syndiotactic polystyrene

“…[1][2][3][4][5][6][7][8][9] However, there are many possibilities. Does the P-I crystal melt to be followed with repacking into P-II, which then melts and repacks into P-III?…”

“…Poly(ether ether ketone) (PEEK), [1][2][3][4] poly(1,4-phenyl sulfide) (PPS), 5 syndiotactic polypropylene (sPP), 6 and oligomeric poly(hexamethylene terephthalate) (PHT) 7 have been reported to exhibit multiple endotherms. Poly(aryl ether ketones) and their copolymers are also known to show multiple melting behavior and have been extensively studied.…”

Dynamic Study of Crystallization- and Melting-Induced Phase Separation in PEEK/PEKK Blends

“…Of the two polymers, PEEK has received more attention thus far, and considerable progress has been made in the understanding of its crystalline structure, [7][8][9][10][11] optical and lamellar morphologies, [12][13][14][15][16][17][18] crystallization kinetics, [19][20][21] and physicochemical properties. 22,23 There are significant differences in the reported results of lamellar structure and lamellar stack dimensions of PEEK.…”

Correlation Between Thermal Behavior and Crystalline Morphology in β-Form Syndiotactic Polystyrene

“…Similar sheaf-like lamellae have been common in several semicrystalline polymers. Marand et al [20] also reported different birefringences of the spherulites in poly(arylene ether ether ketone) attributable to two types of spherulites. In addition, Lawrence and Shinozaki [21] reported coarse sheaf-like lamellae in non-isothermally treated sPS samples (slow cooling rate at 10 8C/min from the molten state), but finer spherulites (with typical Maltese cross) in sPS samples cooled fast at 200 8C/min from melt.…”