Light-Initiated Reactive Processing in FFF 3D Printed High-Performance Polymers

Fused filament fabrication (FFF) is the most popular 3D printing technique; however, FFF structures are inherently anisotropic. Factors such as the high molecular weight of the feedstock polymer and the complex thermal and shear history of the print process inhibits diffusion of polymer chains between printed layers. This leads to weak inter-filament adhesion, which compromises mechanical properties perpendicular to the raster direction. In a previous study by our research group, low-molecular weight additives (LMWA) functionalized with UV reactive moieties were incorporated into a polylactic acid feedstock. During the printing process, these additives surface segregated to the layer interfaces; then, upon irradiation with UV light, crosslinks were formed across the interfaces and nearly isotropic structures were achieved. We have now begun to transition such reactive processing schemes into FFF prints with two high-performance polymers: poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI). This presentation will describe our investigations into the effects of UV/visible light on the mechanical properties of our PEEK and PEI printed structures, again incorporating LMWAs to promote polymer chain diffusivity and small molecule photoinitiators to facilitate reactivity.