M. Adamson, B. Blake, B. Eslami
Widener University,
United States
Keywords: PEEK, 3D Printing, SPM, Multifrequency AFM
Summary:
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. PEEK’s numerous properties include thermal stability, chemical resistance, high tensile strength, stiffness, fatigue resistance, dimensional stability, biocompatibility to utilize within the body, electrical insulation, and a lightweight feel. Despite advancements in the engineering field for the characterization of PEEK, its high melting point (343°C) makes sample preparation and characterization challenging. The findings from this research will help optimize 3D printing parameters for PEEK, improving fabrication efficiency and material quality while contributing to the broader understanding of its surface and mechanical properties. PEEK was characterized at both the nanoscale and macroscale by utilizing Atomic Force Microscopy (AFM) and mechanical testing methods such as tensile and 3-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 macro-scale conditions, providing critical insights into forms of load such as strength and flexibility. The results demonstrate that higher annealing temperatures and longer durations lead to enhanced mechanical properties of PEEK, showing consistent results across both nanoscale and macroscale analyses. A comparison between the PEEK sample annealed at 330°C for 3 hours and the sample annealed at 360°C for 6 hours reveals distinct differences in their structural development. The sample treated at 360°C for 6 hours exhibits a fully melted and solidified cohesive particle network, in contrast to the sample annealed at 330°C, which shows less uniformity and higher surface roughness which indicates little to no network formation. AFM height images reveal that longer annealing times and higher temperatures result in a smoother surface with clearly defined grain boundaries, indicating improved material organization. AFM phase images show a decrease in stiffness as the annealing time and temperature increase, with the phase contrast becoming progressively darker, suggesting greater viscoelastic response and reduced stiffness in the material. These images highlighted the effects of annealing conditions on PEEK’s surface morphology, revealing smoother surfaces and well-defined grain boundaries as annealing times and temperatures increased. This suggests improved material organization, which could enhance the polymer's performance in applications that demand high structural integrity. The ultimate tensile strength results indicate an enhancement due to annealing. The unannealed sample achieved a strength of 84 MPa, whereas the sample annealed at 360°C for 6 hours increased to 90 MPa, highlighting the positive impact of annealing on the material's mechanical performance. The ultimate flexural strength results show minimal variation, consistently averaging around 140 MPa. This consistency suggests that annealing has no significant impact on the flexural strength of the material. Further research is being performed to optimize the printing temperature, flow rate, and other 3D printing parameters to best achieve quality surface finish and dimensional accuracy. This work provides valuable data for future studies and applications involving high-performance polymers, especially within advanced material science and engineering industries.