Molecular weight dependence of weld formation in material extrusion additive manufacturing

Material extrusion (MatEx) additive manufacturing (AM), after several decades of development, is now an established production method for small volume or highly complicated parts. While MatEx has transitioned from prototyping to end use production, little is known about the mechanisms that dominate strength development between layers. Previously we reported on a framework for determining weld time and weld strength of MatEx processed welds, comparing those results to traditional polymer-polymer weld formation. Here we extend that work by systematically varying the weight average molecular weight (M_w) of entangled bisphenol-A-polycarbonate (PC) MatEx filaments and measuring weld time and weld strength. The resulting weld formation will be discussed in the context of traditional polymer-polymer welding and weld thickness during the unique shear and thermal history produced by the MatEx process.