Crystallization kinetics of PEEK nanocomposites with hydroxyapatite and zinc oxide: influence of nanoparticle morphology and hybridization

This study explores the isothermal and non-isothermal crystallization behavior of poly(ether ether ketone) (PEEK) nanocomposites reinforced with hydroxyapatite (HA) and zinc oxide (ZnO), with emphasis on the role of filler morphology and hybridization. Differential scanning calorimetry (DSC) combined with Avrami analysis was employed to investigate crystallization kinetics at multiple temperatures. While conventional nanofillers generally delay crystallization due to hindered chain mobility, the incorporation of 2.5 wt.% flower-like ZnO (fZnO) significantly mitigated this effect, showing crystallization behavior comparable to neat PEEK. In contrast, spherical ZnO (cZnO), HA, and their hybrid systems led to extended crystallization times. Despite variations in crystallization rate, melting temperature (T_m) and equilibrium melting temperature (T_m⁰) remained nearly unchanged, indicating preserved lamellar thickness. The results highlight that nanoparticle morphology strongly influences nucleation dynamics, and fZnO offers a promising strategy to tailor crystallization without compromising crystalline structure. These findings provide key insights for designing high-performance PEEK-based materials for structural and biomedical applications.