Research on the mechanical properties of PEEK material artificial bone implants fabricated by high-temperature air-assisted 3D printing

Abstract

Due to the PEEK material with a melting point of approximately 343 °C and an ambient 3D printing environment temperature of approximately 25 °C, the significant temperature gradient between the extruded PEEK material from the printing nozzle and room temperature restricts the alignment of molecular chains within the material. This thermal condition inhibits the formation of well-ordered crystalline structures, consequently reducing both crystallinity and interlayer bonding strength in printed components. To address this, the printing process incorporates a continuous supply of clean, high-temperature air through a hot air gun. This method maintains elevated component temperatures during fabrication, effectively slowing the cooling rate from processing temperature to ambient conditions. The single-factor and orthogonal experimental results show that high-temperature air significantly improves the mechanical properties of 3D-printed PEEK materials, and 240 °C is the optimal high-temperature air temperature for maximizing the tensile strength and the bending strength of 3D-printed PEEK components in this study environment. The circular (porous) structure of the implant not only exhibits good compressive strength but also provides higher porosity and surface area, which are beneficial for bone cell ingrowth, proliferation, and diffusion. Furthermore, the compressive strength of a pore structure depends not only on its porosity, but also on the shape of the pore. This study provides theoretical guidance for improving the 3D printing quality of high-melting-point, high-viscosity materials and their composites, especially in terms of 3D printing forming temperature and the design of pore structures for porous implants.