Effect of Fabrication Route on the Mechanical Properties of Polylactic Acid (PLA) Composites with Diatom Earth (DE)

Polylactide (PLA) that is reinforced with diatomaceous earth (DE) is a promising and eco-friendly material with high engineering potential. This article provides a comprehensive overview of various PLA types and processing methods for PLA + DE composites. This study aimed to determine the mechanical strength limits of PLA + DE composites using two PLA grades—amorphous PLE 005-A and semi-crystalline Ingeo 4043D—that are each filled with Perma-Guard DE 5, 10, and 15% by weight, and two manufacturing methods, injection molding (IM) and additive manufacturing (3DP), using fused filament fabrication (FFF). The mechanical properties were assessed through static tensile tests in accordance with ISO 527-1 and compared with values reported in the literature. The results indicate a linear increase in stiffness (Young’s modulus) with increasing DE content. This is accompanied by a reduction in maximum tensile strength (σmax) and elongation at break (εb). The highest Young’s modulus, around 4.65 GPa, was observed for injection-molded, semi-crystalline PLA with a 15% by weight DE. The greatest tensile strength, approx. 72 MPa, was achieved for printed, semi-crystalline PLA without filler. Furthermore, 3D printing achieved a tensile strength and stiffness comparable to injection molding, though the latter ensured significantly better ductility. These findings provide a basis for adjusting the PLA + DE composite properties to specific applications by selecting the matrix type, DE content, and manufacturing method.