Search

Additively manufactured, high-performance polymers are increasingly used to realize complex, three-dimensional (3D) products but remain challenging from the point of view of performance control. To correlate and ultimately predict relationships between process parameters and performance, it is essential to advance our understanding of the evolution of the morphology during printing. In this study, we demonstrate spatially resolved, real-time synchrotron wide-angle X-ray scattering analysis during 3D fused filament fabrication (FFF) of poly(ether ether ketone) (PEEK) to map crystallization kinetics during printing at an unprecedented level of detail. Specifically, our measurements provide the first complete 2D map of the crystallization of a deposited road during FFF. This map reveals a sloped crystallization front, with crystallization occurring sooner close to the print bed and increasing monotonically with height. Maps obtained at three different temperatures show an increase in onset time for crystallization with temperature, accompanied by an increase in the final degree of crystallization.

X-ray photon correlation spectroscopy (XPCS) microrheology and conventional bulk rheology were performed on silica nanoparticle dispersions associated with battery electrolyte applications to probe the properties of these specific complex materials and to explore the utility of XPCS microrheology in characterizing nanoparticle dispersions. Sterically stabilized shear-thickening electrolytes were synthesized by grafting poly(methyl methacrylate) chains onto silica nanoparticles. Coated silica dispersions containing 5–30 wt % nanoparticles dispersed in propylene carbonate were studied. In general, both XPCS microrheology and conventional rheology showed that coated silica dispersions were more viscous at higher concentrations, as expected. The complex viscosity of coated silica dispersions showed shear-thinning behavior over the frequency range probed by XPCS measurements. However, measurements using conventional mechanical rheometry yielded a shear viscosity with weak shear-thickening behavior for dispersions with the highest concentration of 30% particles. Our results indicate that there is a critical concentration needed for shear-thickening behavior, as well as appropriate particle size and surface polymer chain length, for this class of nanoparticle-based electrolytes. The results of this study can provide insights for comparing XPCS microrheology and bulk rheology for related complex fluids and whether XPCS microrheology can capture expected macroscopic rheological properties by probing small-scale particle dynamics.