Optimization Scheme for 3D Printing of PLA–PHBV–PCL Biodegradable Blends for Use in Orthopedic Casting

Three-dimensional printing technology offers significant advantages in the production of orthopedic casts, providing a promising alternative to conventional plaster and fiberglass materials. Polylactic acid (PLA) is widely used for this purpose; however, its adoption is limited due to poor mechanical properties, including high brittleness, low thermal stability, and limited elongation. These challenges can be mitigated by blending PLA with other biodegradable polymers. This study investigated a blend of PLA with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a type of polyhydroxyalkanoate (PHA), and polycaprolactone (PCL) for the development of 3D printed orthopedic casts. The key mechanical properties-tensile strength, percent elongation at break, Young's modulus, flexural strength, flexural modulus, and impact strength-were evaluated as a function of the printing parameters, including nozzle temperature, layer height, and raster angle. The grey relational analysis (GRA) approach was applied to optimize these mechanical properties. The optimal printing parameters were found to be a nozzle temperature of 180 °C, a layer height of 0.18 mm, and a raster angle of 0°, resulting in a tensile strength of 44.4 ± 4.4 MPa, an elongation at break of 68.5 ± 11.6%, a Young's modulus of 948.7 ± 25.1 MPa, a flexural strength of 54.6 ± 8.9 MPa, a flexural modulus of 1549.3 ± 141 MPa, and an impact strength of 80.77 ± 5.6 J/m. Statistical analysis using analysis of variance (ANOVA) revealed that for tensile strength, 50.18% was influenced by the raster angle, 26.38% by the layer height, and 18.92% by the nozzle temperature; for flexural strength, 69.81% was influenced by the raster angle, 20.67% by the layer height, and 3.53% by the nozzle temperature; and for impact strength, 75.11% was influenced by the raster angle, 13.16% by the layer height, and 4.45% by the nozzle temperature.