Correlating Microstructural and Rheological Variations in ABS with Interlayer Bond Formation in FFF

Acrylonitrile-butadiene-styrene (ABS) is an amorphous polymer that generally consists of a continuous Styrene-Acrylonitrile (SAN) copolymer phase with dispersed rubbery spherical particles, primarily polybutadiene (PBD), which are grafted with SAN. This microstructure enables ABS to exhibit a complex failure mechanism involving cavitation, crazing, and localized shear yielding. Due to these favorable mechanical properties and its rheological behavior suited for printing, ABS is one of the most used materials for fused filament fabrication (FFF). Despite the availability of a wide range of ABS grades, research on the relationship between ABS microstructure and interlayer bond formation remains limited.

In this study, we investigate these relationships by comparing the impact strengths of as-printed and annealed samples of various ABS grades, each with distinct morphological and rheological characteristics. Notably, ABS grades with a broader PBD particle size distribution and(or) larger PBD particle size exhibit a pronounced annealing effect. We hypothesize that the unique microstructure of ABS inhibits interlayer bond formation during printing due to its unfavorable rheological properties. However, our results suggest that annealing mitigates these initial limitations by increasing interlayer contact pressure and promoting a more even distribution of rubber particles within the interlayer. Morphological and rheological analyses support this hypothesis, helping to elucidate the complex interplay of various ABS properties in FFF.