Mechanical and morphological assessment of kenaf fibers-reinforced nylon for FDM 3D printing of dental prosthesis

Fused Deposition Modeling (FDM) is one of the popular technologies for 3D printing. One significant limitation associated with this technology is the poor mechanical strength of the printed material. In this study, natural fibers (kenaf) were used for nylon filament reinforcement, and were evaluated through mechanical and morphological analysis. Kenaf fibers were submitted to water retting and bleached with 6% sodium hypochlorite solution. Then, the fibers were silanized by 3-aminopropyl triethoxysilane solution before being incorporated with nylon beads using thermal extruder machine. The study groups consisted of control and 0.1%, 0.3%, 0.5%, and 1% kenaf fibers reinforced nylon groups. For morphological analysis, fibers distribution in the filament was assessed through digital microscopic images and FeSEM cross-sectional images. Filament diameter was evaluated using digital caliper. For mechanical analysis, compression and flexural strength tests were conducted on the study samples. Both microscopic and FeSEM analysis revealed fibers distribution parallel to filament extrusion direction except for the 1% kenaf fibers reinforced group that showed some irregular fibers distribution. Filament diameter was not significantly different among the study groups. Mechanical analysis showed that 0.5% kenaf fibers reinforced group was not significantly different from the control group while the rest of the experimental groups were lower than the control group in terms of both compressive and flexural strength. Although kenaf fibers reinforcement with nylon filament showed regular morphological outcome at concentrations of 0.5% and lower, only 0.5% concentration appeared to have no significant effect on the mechanical strength of the FDM printed material, while the other studied concentration showed decreased mechanical strength.