The Role of Multifunctional Octaspherosilicate Additives in Designing Polylactide (PLA)-based Materials: Structure–Property Optimization

Polylactide (PLA), a biobased polymer, has gained significant attention due to its favorable mechanical properties, processability, and applicability in both Fused Deposition Modeling (FDM) 3D printing and conventional manufacturing techniques such as injection molding. However, PLA exhibits pronounced brittleness, necessitating the development of effective property-enhancing modifiers. The incorporation of hybrid inorganic–organic functionalized octaspherosilicates represents a promising strategy to overcome this limitation. Polyhedral oligospherosilicates (RSiMe2O)8Si8O12, analogs of polyhedral oligosilsesquioxanes R8Si8O12, possess a well-defined cubic Si–O–Si core with organosilyl subunits forming a functional crown, enabling modification of polymer properties. Variation in peripheral functional groups (R = H or organic moieties) allows for fine-tuning of material behavior. This study investigates the impact of multifunctional octaspherosilicates on PLA-based materials and their suitability for FDM 3D printing and injection molding.

Organosilicon additives were synthesized via catalytic hydrosilylation and incorporated into molten PLA. A 15% masterbatch was prepared, ground, and subsequently used to produce samples with lower additive concentrations (1 wt% and 2.5 wt%). The modified PLA was processed via two routes: (i) extrusion into filaments followed by 3D printing of test specimens, and (ii) direct fabrication by injection molding. Samples were characterized for their mechanical, rheological, and thermal properties (DSC).

Incorporation of multifunctional octaspherosilicates markedly enhanced the impact resistance of injection-molded samples, reflecting increased ductility. By contrast, 3D-printed specimens exhibited limited improvement in impact strength due to their anisotropic internal structure. Tensile and flexural strengths of 3D-printed samples were only slightly lower than those of injection-molded specimens, demonstrating the efficacy of the modifiers across both processing routes. Rheological measurements and SEM-EDS analysis confirmed good phase homogeneity and strong interfacial compatibility. Organosilicon additives functioned as lubricating agents, promoting polymer chain disentanglement and increasing free volume in the melt, thereby contributing to the observed enhancements in material properties.