Preparation and characterization of poly(ether ether ketone)/poly(ether imide) [PEEK/PEI] blends for fused filament fabrication

The present study focuses on the preparation and characterization of a poly(ether ether ketone)/poly(ether imide) [PEEK/PEI] blend for application in additive manufacturing using fused filament fabrication (FFF). Polymer miscibility was evaluated using differential scanning calorimetry analysis and Fourier transform infrared analysis. The results confirmed the full miscibility of PEEK and PEI at all compositions. Seen as the best compromise between mechanical properties and glass transition temperature, a 70/30 wt/wt% PEEK/PEI blend was extruded into filaments for use by FFF. Nozzle temperature, layer orientation, and layer thickness were selected as printing parameters to evaluate their effect on the tensile properties and degree of crystallinity ( $${{X}}_{\mathrm{c}})$$ . Optimum printing parameters were achieved at 380 °C nozzle temperature, a [0/15/−15°] layer orientation, and a 0.15 mm layer thickness. The printed PEEK/PEI samples were annealed at various temperatures to erase residual thermal stress generated during printing. Samples annealed for two hours at 200 °C have improved elastic modulus by 21.6%, while $${{X}}_{\mathrm{c}}$$ increased by 24.3%. Adding 30 wt% of PEI to the semicrystalline PEEK yielded three advantages, namely improving the operating and service temperatures by 20 °C, decreasing the processing temperature by 20 °C while maintaining most of the high tensile properties of PEEK.