Valorization of purified agricultural brown eggshell by-product as filler in bio-epoxy composites

This study presents tensile, flexural and water absorption properties of composites made from bio-epoxy resin containing brown eggshell (with membrane), purified brown eggshell (without membrane) and mineral limestone at three filler levels of 5, 10 and 20 wt%. Composites were made by an open silicone mold casting method. Fourier transform infrared (FTIR) spectroscopy was used to demonstrate removal of the membrane. Inductively coupled plasma mass spectrometry (ICP-MS) indicated brown eggshells without membrane had a higher calcium carbonate content suggesting the purification technique worked well. Although composite tensile strengths and flexural strengths were lower than the pure bio-epoxy, the composites containing brown eggshells (with membrane) had slightly better strengths than composites containing purified brown eggshells (without membrane) and mineral limestone for the same particle size of 32 µm. The organic membrane contains proteins on the surface of the eggshells which may be beneficial for chemical bonding to occur with the bio-epoxy resin. Filler contents of 5–10 wt% were acceptable for tensile and flexural strengths. Scanning electron microscopy (SEM) provided visual observations of the fractured surfaces where an increase in surface roughness was related to an increase in filler loading, implying changes occurred within the composite materials. Brown eggshells can be exploited as a waste management opportunity for use as a filler in bio-epoxy composites.