Fused Filament Fabrication of Polymer Blends with in situ Layerwise Chemical Modifications

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Date

2023

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University of Texas at Austin

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The layerwise paradigm of additive manufacturing advertises voxel level control over both geometry and material properties of parts although the latter is difficult to achieve. Recently the Savannah River National Laboratory has demonstrated a new technique for voxel level material property control via layerwise surface chemical modification of polycarbonate homopolymer with UV and ozone during manufacturing. This technique can be utilized to modify each respective phase of a blended polymer feedstock to increase chemical similarity in preparation for potential in situ interphase crosslinking. Successful crosslinking of dissimilar polymers during manufacturing could allow for further voxel level material property control than modification of a homopolymer could allow. Test feedstock comprised of melt mixed polycarbonate and polystyrene homopolymers, an immiscible polymer blend, were printed in an atmosphere containing ozone and UV light. FTIR measurements indicate both phases of the blend may be modified simultaneously in situ to form new oxygen functional groups, increasing chemical similarity. Calorimetric and thermomechanical characterization show no indicators of increased compatibilization due to the treatment. Uniaxial tension to failure experiments demonstrates minimal loss of mechanical properties as the blend phase to phase interfacial properties dominates the behavior despite the chemical modifications. Future work will focus on understanding the complex relationships between configurable processing parameters (layer height, print speed, temperature, etc), reaction site creation density, and blend degradation prior to further modification while identifying a suitable crosslinker to improve mechanical and thermal properties of the blend.

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