Formulations of Starch-based Adhesive Variants Using Eggshell and Snail Shell as Fillers

Abstract

The environmental and health risks associated with petroleum-derived synthetic adhesives underscore the urgent need for sustainable alternatives. This research examines starch-based adhesives augmented with calcium carbonate (CaCO₃) sourced from waste materials of eggshells and snail shells for the purpose of paper bonding. Starches obtained from cassava, yam, and maize were synthesized with eggshell-derived CaCO₃, snail shell-derived CaCO₃, and laboratory-grade CaCO₃. Mechanical properties were assessed through tensile lap-shear and T-peel tests, while molecular interactions were elucidated employing FTIR spectroscopy. Yam starch combined with snail shell-derived CaCO₃ attained the highest shear strength of 7.69 MPa, representing a 39% enhancement relative to the control. FTIR analysis indicated that yam starch inherently contains mineral carbonates at 1422 cm⁻¹, which elucidates its distinctive compatibility with the aragonite form of snail shell (1451 cm⁻¹) compared to the calcite form from eggshells (1420 cm⁻¹). All filler types exhibited reliable performance when combined with cassava starch, which yielded shear strengths ranging from 4.75 to 5.60 MPa. The native hydrogen bonding network was preserved in the yam-snail shell composite, whereas the formulation with yam and eggshell significantly compromised this network, resulting in suboptimal performance. Yam starch adhesives are successfully reinforced with CaCO₃ derived from agricultural waste, particularly snail shells, thereby providing a viable, sustainable alternative to synthetic adhesives.