PLA Reinforced with Limestone Waste: A Way to Sustainable Polymer Composites.

Waste stone sludge generated by the extractive industry has traditionally posed significant disposal challenges. This study redefines stone sludge as a valuable raw material by incorporating it into polylactic acid (PLA) to create sustainable composite materials. Pellets and filaments composed of up to 50% by weight of limestone powder and PLA were successfully produced using melt blending in a twin-screw extruder. Scanning electron microscopy (SEM), X-ray fluorescence (XRF), and X-ray diffraction (XRD) analyses revealed a uniform distribution of stone particles within the PLA matrix and confirmed the chemical and structural compatibility of the components. Thermogravimetric analysis (TGA) showed that the composites retained thermal stability, while mechanical testing demonstrated significant enhancements in stiffness, with an increase in elastic modulus for composites containing 50% limestone powder. The melt flow rate (MFR) decreases with increasing filler content. The brittleness also increased, reducing impact resistance. Mechanical tests were performed on injected and 3D-printed specimens. The filament produced was successfully used in 3D printing, with a small XYZ calibration cube.