Influence of Heat Treatment on the Mechanical and Chromatic Properties of Polyetheretherketone‐ TiO 2 Composite Manufactured Using Fused Deposition Modeling

ABSTRACT This study systematically investigated the effects of heat treatment parameters (temperature, holding time, and heating rate) on the microstructure, mechanical and chromatic properties of fused deposition modeling (FDM)‐fabricated polyetheretherketone (PEEK)‐TiO 2 composites through 16‐run orthogonal experimental design ( n = 5 per group). Results demonstrated that heat treatment temperature significantly influenced tensile modulus, flexural strength/modulus, and color difference (ΔE 00 ) ( p < 0.05), while holding time only affected flexural modulus ( p < 0.05). Optimal parameters (300°C, 60 min, 12°C/min) yielded maximum mechanical properties: tensile strength (91.66 MPa) and modulus (3867.16 MPa) increased by 85.36% and 62.61%, while flexural strength (154.63 MPa) and modulus (3947.84 MPa) improved by 47.87% and 53.21%, respectively, compared to untreated samples. This enhancement was attributed to the notably improved structural density with a low porosity (1.58%) and more ordered microcrystalline structure of the composite. Meanwhile, the colors of all the PEEK–TiO 2 specimens darkened, tending toward red and yellow, with a color difference (ΔE 00 ) ranging from 2.04 to 7.67, exhibiting significant negative correlations with changes in crystallinity ( p < 0.001). This work demonstrates the feasibility of enhancing the mechanical properties of the composite through heat treatment and highlights the potential of modulating the crystal structure in regulating the chromatic properties of composites for oral applications.