Enhancing surface properties of FFF 3D printed nylon reinforced with kenaf fibres for dental prosthesis construction: An ANOVA-based analysis

Fused filament fabrication (FFF) is a printing technology that relies on remelting and modelling physical objects from thermoplastic filament materials. Natural fibres have been studied and used for polymeric reinforcement. Yet, there is limited information in the literature about reinforcing filament materials for FFF printing. This study aimed to evaluate some surface properties of FFF 3D printed polyamide 6 reinforced with kenaf fibres. Kenaf fibres were retted, bleached with sodium hypochlorite solution, and silanised with 3-aminopropyltriethoxysilane solution prior to thermally compounding with polyamide beads to produce filaments for experimental groups. A total of 55 specimens were printed by an FFF printer for 5 groups: control, 0.1%, 0.3%, 0.5% and 1% kenaf fibres-reinforced polyamide (11 specimens for each group). Fourier-transform infrared spectroscopy analysis was conducted on the control and 1% kenaf-reinforced sample for chemical characterisation. The study groups were submitted to surface roughness, surface hardness and water contact angle measurement tests. The results showed no significant chemical change in the composite as a result of fibre incorporation. Surface hardness have shown a significant increase in their mean values after fibres incorporation, which were 93.3, 93.5, 92.2, 91.3 for 0.1, 0.3, 0.5 and 1% respectively compared with the control 88.9, while there was no significant difference in both surface roughness and surface hydrophilicity except for 1% kenaf-reinforced group (roughness = 358, contact angle = 55.1) compared to the control group (roughness = 216, contact angle = 46.4). Kenaf fibres reinforcement with polyamide 6 at concentrations not more than 0.5% has improved the surface hardness of the FFF printed material.