Compatibility-driven modulation of mechanical property in 3D printed PEEK blends

Additive manufacturing of poly ether ether ketone (PEEK) is increasingly used to produce complex three-dimensional (3D) products, but controlling interlayer performance remains challenging. To address this, we synthesized a series of rigid fluorene-containing amorphous polymers by systematically modulating the molar ratio of resorcinol to bisphenol fluorene with varying compatibility with PEEK. These polymers were then blended with PEEK to investigate the compatibility effects on interlayer properties. A relationship among interlayer strength and the diffusion and entanglement of polymer chains was established. Isothermal crystallization studies revealed that blending with amorphous polymers extends the crystallization time of PEEK and enhances interlayer healing, thereby improving interlayer strength. Atomic force microscopy-infrared tests confirmed the accumulation and diffusion of amorphous and partially compatible fluorene-containing polymers at the interface of the blends, which enables the best-performing blends to have three times the interlayer strength of pure PEEK. These findings provide valuable insights into the molecular chain dynamics during printing, supporting the development of materials with optimized interlayer properties.