Valorization of fish scale waste: a comparative assessment of the physicochemical properties of water-, acid- and alkali-treated fish scales in developing fiber-reinforced composites

Abstract

The disposal of fish scales (FSs), a proteinaceous waste material, is a challenging task, especially in underdeveloped countries. The reuse of this abundant undervalued resource to manufacture green composites is a sustainable approach to maintain the ecology by reducing waste and carbon footprint and fostering prosperity through innovative economic opportunities for fish sellers. This study investigates the utilization of fish scales as a sustainable reinforcement material and maleic anhydride-modified acrylated epoxidized soybean oil (MAESO) as the matrix for green composite development, with an emphasis on optimizing the surface treatment of FS for improved performance. Fish scale waste was subjected to water, acid and alkali treatments, and the physicochemical properties were studied in order to optimize the most suitable method of treatment. Both the treated fish scales and composites were characterized using various analytical techniques. Water-treated FS exhibited superior mechanical performance, achieving a tensile strength of 267 MPa compared with 147 MPa and 52 MPa for the acid- and alkali-treated samples, respectively. Composites reinforced with water-, acid-, and alkali-treated fish scale powder (FSP) exhibited tensile strengths of 4.38, 4.08, and 3.78 MPa, respectively, and their flexural strengths were 5.64, 3.81, and 2.80 MPa, respectively. The water-treated composite also exhibited maximum hardness (Shore D 65) and impact strength (60.81 J m⁻¹). Overall, the water-treated FSP-based composites demonstrated better mechanical, thermal, and chemical resistance, as well as reduced water uptake. These findings demonstrate the potential of fish scale-derived materials as eco-friendly, value-added fillers for sustainable composite applications.