Taguchi design and optimization of the PLA/PCL composite filament with plasticizer and compatibilizer additives for optimal 3D printing

3D printing (3DP) has brought endless possibilities to the manufacturing industry. Biodegradable high-polymer materials such as polylactic acid (PLA) and polycaprolactone (PCL) have attracted widespread attention. However, to optimize printing performance, this study prepared six PLA/PCL composite materials with ratios of 4:6, 5:5, and 6:4, by adding Polyethylene Glycol 4000 (PEG 4000) as a plasticizer and nano silica as a reinforcing agent. Parameters that can affect printing quality, including formulation, printing temperature (150, 170, and 190 degrees C), filling density (305, 40%, and 50%), and printing speed (20, 30, and 40 mm/s), were examined and optimized. The optimal factor level combination determined by Taguchi fractional factorial design were silica addition 0.6 g, PLA content 60 wt%, printing temperature 190 degrees C, infill density 50%, and printing speed 20 mm/s. The obtained minimum error value was 0.338 mm. Analysis of variance revealed the statistical significance of PLA content and printing temperature. A general linear model was established for result prediction, showing a difference of 9.25% from the actual error values. SEM results indicated poor compatibility between PLA and PCL in the meltblended mixture, while the addition of SiO2 nanoparticles facilitated PCL and PLA crystallization. DSC analysis demonstrated that the incorporation of PLC and SiO2 led to an increase in crystallinity, with 5PLA/5PCL/SiO2 exhibiting the highest crystallinity at 51.4%. Tensile testing results showed that the addition of 50 wt% PCL to PLA significantly improved the fracture elongation of the PLA/PCL material with a 5:5 formulation, averaging about 4 times higher than that of pure PLA, while the tensile strength decreased by 1.5 times. This study not only expands the research on PLA/PCL blends but also provides process guidance for 3D printing of the materials.