The formulation and study of the thermal stability and mechanical properties of an acrylic coating using chicken eggshell as a novel bio-filler

•Smaller particle size of bio-filler showed better interfacial bonding.•Smaller particle size of bio-filler showed uniformity in composition.•Thermal stability improved with decreasing particle size of bio-filler.•Bonding strength improved with decreasing particle size of bio-filler. The objective of this study was to evaluate the effect of chicken eggshell (ES) as a bio-filler on the adhesion strength and thermal stability of acrylic coatings. The influence of different particle sizes of ES on the performance of acrylic coatings was compared with commercial calcium carbonate filler by using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and pull-off type equipment. The surface morphologies of the coatings were characterized through field emission scanning electron microscopy (FESEM). The resistance of the coating was also investigated using water immersion and freeze–thaw tests. Morphological studies revealed that the ES filler was well-distributed in the polymer matrix. Furthermore, it was observed that the adhesion strength, thermal properties, water and freeze–thaw resistance of the coating improved with decrease in particle size of ES filler. Overall, the best results were obtained from using ES bio-filler with the smallest particle, although the particle size was bigger than that of commercial calcium carbonate. The improvement in the properties of the coating was attributed to the even distribution of ES particles and better ES/matrix interface.