Additive Manufacturing of Polyamide 66: Effect of Process Parameters on Crystallinity and Mechanical Properties

In this study, polyamide 66 (PA 66) filaments were prepared for fused filament fabrication (FFF). The effects of the process parameters on the mechanical properties, initial microstructures, dynamic mechanical behavior, and crystallinity of the samples were investigated. The samples obtained at high processing temperatures exhibited high crystallinity, high tensile strength, and low porosity. Almost fully dense samples with excellent mechanical properties were obtained under optimal conditions. The tensile strength of the samples improved by 29.5% (from 68.07 to 88.17 MPa) with an increase in the nozzle temperature from 270 to 290 °C. The elongation at break abruptly increased (from 2.38 to 13.17%), because of the plastic behavior of the material and strain hardening. X-ray diffraction results demonstrated that the crystallinity of PA 66, significantly improved (from 47.3 to 65.6%). In addition, the dynamic mechanical performance of the samples was significantly related to the raster angle. The samples fabricated at a raster angle of 0° exhibited the best dynamic mechanical properties, followed by the 45° and 90° samples. The successful fabrication of PA 66 samples demonstrates the potential use of PA 66 for producing parts using FFF, and provides options for utilizing materials with improved performance for additive manufacturing applications in engineering.