Mica filled polyetherketoneketones for material extrusion 3D printing

Polyetherketoneketone (PEKK) has superior physical properties to most available thermoplastics compatible with material extrusion-based 3D printing. The performance of fused filament fabrication (FFF) compatible PEKK has been detailed primarily as a function of varying the isomer ratios composing the co-polymer structure. PEKK composite or blend development for AM has received limited attention, yet this strategy is attractive for further performance tailoring and to address challenges associated, for example, with shrinkage upon crystallization. Here, we report the integration of three grades of mica platelets into PEKK at 10% and 30% mass loadings to generate an array of filament feedstocks that were used to print objects with a simple FFF machine. The effects of mica coating chemistry on the compatibility with PEKK and resulting properties are described. Mica fillers have only subtle influence on the FFF relevant melt rheological properties inherent to PEKK. Pigment micas at high loadings reduce the melting temperature of PEKK without shifting its glass transition temperature or inducing undesirable crystallization during processing. The printed composites were effectively cold crystallized post-printing similarly to unfilled PEKK resulting in increased dimensional stabilities. All micas, when used as fillers in low and high relative PEKK crystallinities, increased the tensile modulus of parts in correlation to the loading. The microstructural features of a printed composite were compared to unfilled PEKK by use of high-resolution helical micro-computed tomography. Practically, pigment micas can confer a wide range of rich colors to 3D-printed PEKK.