Thermal and mechanical evaluation of untreated kenaf fiber-reinforced nylon for FDM 3D-printed dental prostheses

Fused Deposition Modeling (FDM) 3D printing is utilized in dental appliances and prosthesis construction, eliminating the need for the complex laboratory procedures. One major downside of this technology is the poor mechanical properties. This study aimed to evaluate the reinforcement of nylon filament with untreated kenaf fibers for FDM 3D printing in terms of mechanical properties. Raw kenaf fibers were submitted to water retting, dried, ground, and sieved. The resulted fibers were combined with nylon beads at a concentration of 1 wt%. The modified nylon mix was used to produce filament by thermal compounding technique. The modified filament was used to print the experimental group’s specimens while the as-received nylon filament was used to print the control specimens. Each group consisted of 5 specimens assigned for each testing method. Thermogravimetric analysis and differential scanning calorimetry was performed to the study samples. The mechanical evaluation was based on compressive strength, flexural strength, and surface hardness tests. The results were analyzed for significant difference by IBM SPSS software. Differential scanning calorimetry displayed optimized thermal stability after reinforcement. Although the mean value for compressive strength for the fiber-modified group was higher than the control group (49.34 ± 4.02 MPa and 45.02 ± 5.13 MPa, respectively), no statistically significant difference was observed between the groups (p-value >.05). However, there was a significant decrease in flexural strength for the fiber-modified group compared with the control group (23.23 ± 12.65 MPa and 43.14 ± 3.02 MPa, respectively) and p-value <.05. Surface hardness results showed no significant difference between the groups mean values (106.1 ± 1.14 for the control group, and 105.4 ± 1.85 for the fiber-reinforced group) with p-value >.05. The findings suggest that untreated kenaf fiber-reinforced composite at 1 wt% could provide acceptable mechanical behavior in applications require compression strength and scratching resistance. However, it may not tolerate bending stresses as expected.