Post-Processing PEEK 3D-Printed Parts: Experimental Investigation of Annealing on Microscale and Macroscale Properties.

Polyether ether ketone (PEEK) is a high-performance thermoplastic polymer known for its unique combination of properties that make it suitable for a wide range of applications. Despite significant advancements in the characterization of PEEK, its high melting point (343 °C) presents challenges in both sample preparation and post-processing treatments such as annealing. Due to the high melting temperature of PEEK, there is a large change in temperature that occurs during the deposition of each layer during the print, causing a lack of strong adhesion between each filament layer. Therefore, annealing becomes a necessary post-processing step to ensure strong bonding within the parts. Hence, there is a need to establish precise post-processing parameters to enhance the material's structural integrity and performance. This study aims to characterize PEEK at both the nanoscale and the macroscale by utilizing Atomic Force Microscopy (AFM) and mechanical testing methods such as tensile and three-point bending tests. AFM imaging, which offers high-resolution surface analysis, was used to assess PEEK's surface morphology before and after annealing, providing insights into roughness, mechanical properties, and structural integrity at the nanoscale. Tensile and bending tests evaluated PEEK's mechanical performance under macroscale conditions. Microscale AFM revealed that annealing at higher temperatures and for longer durations enhances polymer chain mobility. This promotes structural reorganization, recrystallization, and a reduction in surface roughness. These findings correlate to the macroscale properties where the tensile strength of the sample with the longest annealing duration and highest temperature increased 6.0 MPa from the sample that was not annealed. Three-point bending tests showed a 16 MPa increase from the unannealed sample to the sample annealed at 360 °C for 6 h. The findings from this research will help optimize post-processing parameters for PEEK, improving material quality while contributing to the broader understanding of its surface and mechanical properties. This work provides valuable data for future studies and applications involving high-performance polymers, especially within engineering and biomedical fields.