30% PPC and 1% TBT dramatically improve PLA 3D printing performance!
Polylactic acid (PLA), one of the primary raw materials for 3D printing, boasts advantages such as being pollution-free, environmentally friendly, biodegradable, and biocompatible. However, PLA's shortcomings, such as poor impact strength, high rigidity, and poor toughness, significantly limit its applications.
To address this issue, Shenyang University of Chemical Technology graduate student Jin Shuai and his advisor Shi Ying used PPC to toughen PLA. They studied the effects of PPC addition on PLA's thermal, crystallization, and mechanical properties, identifying the optimal toughening solution.
First, using biodegradable polypropylene carbonate (PPC) as the toughening raw material, PPC was melt-blended with PLA. The PLA/PPC blend was then subjected to FDM 3D printing and injection molding. The effects of 3D printing and injection molding processes on the flowability, thermodynamic properties, crystallization behavior, impact strength, and cross-sectional morphology of PLA/PPC blends were investigated. The effect of varying PPC addition levels on the toughening of PLA was also investigated.
Sample Formulation
The results showed that, for injection molding, the addition of 30wt% PPC significantly improved the flowability of PLA. The addition of 30wt% PPC enhanced the mobility of PLA molecular chains, reaching a maximum crystallinity of 31.7%. This achieved the best toughening effect on PLA, and cross-sectional morphology analysis also demonstrated the optimal toughening effect at 30wt%. For 3D-printed samples, the crystallinity of PLA/PPC was lower than that of injection-molded samples, and the impact performance of the printed samples was also lower than that of the injection-molded samples. Similarly, cross-sectional impact morphology analysis revealed brittle fracture. Therefore, there is significant room for improvement in the various properties of 3D-printed samples compared to those processed by injection molding.
Thermomechanical Properties of 3D-Printed PLA/PPC/TBT Blends
Secondly, tetrabutyl titanate (TBT) was added as a compatibilizer to PLA70/PPC30 blends after the addition of 30 wt% PPC. The effects of TBT on the fluidity, thermal properties, and crystal structure of the blends were investigated. Results showed that the addition of TBT improved the fluidity and melt index of the PLA/PPC blends. However, the addition of TBT significantly reduced the crystallinity of the PLA/PPC blends, reaching only 4.4%. However, mechanical property testing showed that the tensile and impact strengths of the 3D-printed parts with TBT were greater than those without TBT.
PLA/PPC (a) and PLA/PPC/TBT (b) tensile bars printed at different temperatures
Finally, the PLA/PPC/TBT blends were 3D-printed, and the material molding process was optimized by varying the 3D printing parameters. Mechanical property testing revealed the optimal printing parameters: print temperature 230°C, build plate temperature 65°C, layer height 0.1mm, wall thickness 1.2mm, print speed 30mm/s, and infill density 100%. These printing parameters ensure the production of products suitable for practical applications. As a compatibilizer, TBT significantly improves the compatibility between PLA and PPC, maintains minimal thermal properties of the blend, and enhances its fluidity, making it more suitable for 3D printing.
