Material Formulation and Process Optimization Towards Fabricating Robust 3D Printed Structures

This dissertation focuses on understanding and addressing the fundamental physicochemical phenomena that lead to weak interfaces and structural warpage in material extrusion 3D printing. Polymeric feedstocks used for this manufacturing technique were manipulated through the incorporation of additives that alter the dynamics of the matrix during and after printing. In Chapter II, adhesion between layers of structures printed from PEEK was strengthened through a combination of low-molecular weight additive incorporation and post-printing thermal annealing. Chapter III reports a method for decreasing the irreversible thermal strain of structures printed from poly(lactic acid) by introducing nanographene and photoinitiator additives into the feedstock and printing with in situ ultraviolet illumination. Chapter IV describes follow-up work in which a similar approach was taken to decrease the irreversible strain of structures printed from the high-performance polymer poly(ether ether ketone). Finally, Chapter V explains how synchrotron wide-angle X-ray scattering can be used to analyze the interfaces between printed layers. The data presented in this chapter demonstrates how polymeric additives modify the crystallinity of the bulk polymer matrix, leading to augmented interfacial strength.