Using High Performance Additives in Fused Filament Fabrication to Improve Mechanical Properties

Fused filament fabrication (FFF) is an extrusion-based additive manufacturing (AM) technique that uses thermoplastic filaments as the feedstock material to build objects from printed layers. The layer-wise build approach of this technology allows for tremendous flexibility in design, however there are a limited number of feedstock materials that produce printed structures with robust mechanical properties. Printed structures made by FFF usually suffer from mechanical anisotropy due to poor interfacial bonding of the filament material between successive layers. This introduces voids throughout the printed structure that act as stress concentrators and, as a, result the mechanical properties of FFF printed parts are inferior compared to the properties of the bulk material. This dissertation work focuses on developing stronger feedstock filament materials for FFF by polymer blending. To accomplish this I explored strategies for synthesizing and preparing polymer additives for polymer feedstocks. In addition, I examined how incorporating an engineering thermoplastic with excellent mechanical properties poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) affects the mechanical properties of three commodity thermoplastics, polystyrene (PS), poly(acrylonitrile-styrene-acrylate) (ASA), and poly(acrylonitrile-butadiene-styrene) (ABS). The mechanical properties of each of these polymers were enhanced with the addition of PPO at low loading levels. Furthermore, ToF-SIMS analysis was conducted to assess the dispersion of PPO in the matrix polymers (ASA and ABS) at various loading levels. The results from this study strongly suggest that PPO is well distributed on the surface of the printed specimens. This demonstrates that is a polymer blending specifically by solution casting promotes uniform dispersion and distribution of polymer additives into intricate phase-separated matrices. These studies also show that polymer blending is a simple and yet powerful approach for developing new polymer-based feedstock materials with robust mechanical properties for printing by FFF.