Reducing Anisotropy in FFF Printed High-Temperature Thermoplastic Polymers: The importance of Crystallization

Limiting anisotropy in the design of geometrically complex and 3D printed structures via material extrusion additive manufacturing (or 3D printing) remains a critical issue that hampers the widespread adoption of the technology. Fused filament fabrication (FFF), in particular, is the most widely used 3D printing approach However, due to the complex shear and thermal history that the material experience in the printing process, weak inter-filament bonding ensues due to incomplete polymer diffusion, causing significant mechanical anisotropy in the final parts. To improve this interfacial adhesion and tailor polymer diffusion, our research group has previously incorporated low-molecular-weight (LMW) additives into poly(lactic acid) (PLA) and acrylonitrile butadiene styrene (ABS) polymer blends that surface segregate which improves interfacial adhesion and enhances mechanical properties of the printed structures. This talk will focus on transitioning these concepts to FFF of high temperature polymers, such as poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI). Specific areas of investigation include formulating multimodal blends of polymer molecular weights to control polymer diffusion during printing, as well as control of the distribution of crystalline PEEK through processing and post-processing protocols. In particular these results will emphasize the importance of controlling the crystallization of the PEEK in these studies.