(651i) Important Considerations That Drive the Flow-Induced Crystallization of the Rod-like Polymer Poly(ether ether keytone)

Poly(ether ether keytone) (PEEK) is a rod-like polymer that undergoes flow-induced crystallization (FIC) via a different mechanism than flexible semicrystalline polymers. Specifically we have shown that PEEK undergoes a the novel shear-induced isotropic-nematic transition in the melt, and that this transition is stress controlled. Birefringence measurements obtained during shear flow will be discussed and used to explain the importance of shear flow on this nematic transition. In addition, composites of PEEK were prepared with carbon nanotubes (CNT) at a series of loading levels, and it was confirmed that CNT act as strong nucleators for PEEK in the quiescent state, flow-induced crystallization experiments were conducted to explore the potential competition or acceleration effects of CNT in PEEK during FIC. We determined that even very low levels (0.01%) of CNT completely dominated any influence of FIC in the PEEK melt, both under isothermal and non-isothermal crystallization conditions, both of which were explored using standard (DSC) and fast-scanning calorimetry (FSC). Morphology was strongly influenced by the presence of both flow and CNT, and microstructure will be discussed from studies involving samples first prepared using the FSC and then evaluated using atomic force microscopy (AFM). In addition, the role of micro-fillers (glass filled and carbon fiber filled) will be discussed. Interestingly, the importance of these larger, high-aspect ratio fillers seems to be related to the orientation developed in the melt, which ultimately can increase FIC independent from the quiescent nucleating effect.