In-Situ/Operando X-ray Photon Correlation Spectroscopy Studies of Polymer Dynamics During 3D-Printing of Dual-Cure Polymer Epoxy

Synchrotron-based X-ray Photon Correlation Spectroscopy (XPCS) was used to probe the dynamic properties of soft matter at relevant size (submicrons) and time-scales (milliseconds). We combined XPCS with in-operando capabilities of synchrotron beamlines to shed light onto the unexplored dynamics of dual-cure (UV/thermal) industrial polymers for advanced 3D printing applications. We studied, in operando: a) the structural evolution and corresponding dynamics of the polymer during the extrusion phase of 3D printing, b) anisotropic structure formation & interfacial behavior during subsequent settling and UV curing, and c) the process of final thermal cure. The results revealed a) anisotropic polymer dynamics in different directions (printing (horizontal) vs. extrusion (vertical)) during printing and settling of the material, b) two-stage crosslinking dynamics during UV curing, and c) the chain dynamics near the polymer-polymer interface between 3D-printed filaments as a function of the distance from the interface. The present study shows that an in-situ/ operando XPCS is not only an excellent technique for comprehensive, quantitative characterization of 3D printing processes, but also provides an unprecedented opportunity to perform studies of a wide variety of nonequilibrium phenomena of polymeric materials under external stimuli.