Isothermal crystallization behavior of nano-alumina particles-filled poly(ether ether ketone) composites

The isothermal crystallization behavior of nano-alumina particle-filled poly(ether ether ketone) (PEEK) composites has been investigated using differential scanning calorimeter. The results show that all the neat PEEK and nano-alumina-filled PEEK composites exhibit the double-melting behavior under isothermal crystallization. The peak crystallization times (τ _p) for all the neat PEEK and PEEK/aluminum oxide (Al ₂O ₃) composites increase with increasing crystallization temperature. Moreover, the crystallinity of the PEEK/Al ₂O ₃ composite with 7.5 wt % nano-filler content reached the maximum value of 44.8% at 290°C, higher than that of the neat PEEK polymer. From the lower value in τ _p and higher value in X _c for the PEEK/Al ₂O ₃ composites, the inclusion of the nano-alumina into the PEEK matrix favored the occurrence of heterogeneous nucleation. The Avrami exponents n of all the neat PEEK and PEEK/Al ₂O ₃ composites ranged from 2 to 3, and the n values for PEEK/Al ₂O ₃ composites were slightly higher than that of the neat PEEK polymer, indicating that the inclusion of the nano-filler made the crystallization mechanism more complex. However, the growth rate of crystallization was lowered as the nano- filler was introduced, and the decrease in growth rate reduced the grain size of the PEEK spherulites because of the lowering of molecule mobility during isothermal crystallization.