Crystallinity, Porosity, and Microstructure of Polyphenylene Sulfide Composite Parts Fabricated by Filament‐Extrusion Additive Manufacturing

ABSTRACT Polyphenylene sulfide (PPS) was compounded with recycled carbon fibers (rCF) and thermal black (TB) particles, followed by injection molding (IM) and extrusion of the compounded composites into filaments for fused filament fabrication (FFF). The effect of rCF and TB contents on the microstructure, crystallization kinetics, and mechanical performance of the PPS composites was evaluated and analyzed. At the incorporation of 20 wt.% rCF, the tensile strength of IM specimens increased from 73 MPa up to 151 MPa, and the tensile modulus increased from ~3.5 GPa up to ~20 GPa, respectively. FFF printed specimens with 20 wt.% of rCF showed a tensile strength of 86 MPa and a tensile modulus of 6 GPa, higher when compared to IM neat PPS. Crystallization kinetics of extruded pellets, IM, and FFF printed PPS composites were investigated. The results revealed that the incorporation of rCF and TB significantly hindered the crystallization of PPS. The microstructural characterization provided quantitative results for porosity content and the length distribution and deviation angle of rCF. These characterizations helped to analyze the mechanical performance of IM and FFF printed parts, providing quantitative results to explain the differences in mechanical properties of specimens fabricated through the two methods.