Starch consolidation of calcium carbonate as a tool to develop lightweight fillers for LDPE-based plastics

Calcium carbonate (CaCO₃) is used as a filler to improve the stiffness and processability of plastics at low cost. However, its high density limits the quantity to be used. In this work, the feasibility of using starch consolidation of eggshells-derived CaCO₃ (ES) to develop lightweight fillers for low density polyethylene (LDPE)-based materials was studied. Starch, recovered from potato by-products, was combined with ES, gelatinized, dried, and milled as a fine powder. The obtained ES/starch-based particles were then compounded with LDPE and their influence on chromatic, mechanical, morphological, and density properties of mold injected LDPE-based materials was studied. Commercially available CaCO₃ (COM) was used as control. ES/starch particles were 18 times less dense than the commercially available CaCO₃ (2.62 g cm^-3). When incorporated into LDPE-based formulations, ES/starch originated brownish materials with lower density (1.18 g cm^-3) and higher stiffness (542 MPa of Young's modulus) than those produced with the COM sample (1.33 g cm^-3 of density; 221 MPa of Young's modulus). Therefore, starch consolidation of ES revealed to be a promising approach to develop lightweight fillers able to provide stiffness and color to LDPE-based plastics, while valorizing biomolecules-rich by-products.