Production and Physicochemical Characterization of Waste Polystyrene and Polyethylene Pyrolysis Oil Blends as Sustainable Binder for Emulsion Paint Production

Abstract

The increasing accumulation of plastic waste and the high dependence of paint industries on petroleum-derived binders have created a need for alternative materials from waste resources. This study investigated the production and physicochemical characterization of pyrolysis-oil blends derived from waste polystyrene (PS) and polyethylene (PE) for potential application as binders in emulsion paint production. Waste PS and PE collected from municipal solid-waste streams in Yola, Adamawa State, Nigeria, were cleaned, size-reduced, and separately converted into pyrolysis oils under oxygen-limited conditions. The oils were blended at PS/PE weight ratios of 90/10, 80/20, 70/30, 60/40, and 50/50. The blends were evaluated for viscosity, pH, density, refractive index, moisture content, turbidity, water dispersibility, pour point, elongation at break, and Fourier Transform Infrared (FTIR) characteristics. The results showed that increasing PE content generally reduced viscosity, density, refractive index, and elongation at break, while increasing moisture content, turbidity, and pour point. Viscosity decreased from 378 mPa·s in the 90/10 blend to 187 mPa·s in the 50/50 blend. The selected 80/20 blend exhibited a viscosity of 342 mPa·s, pH of 4.38, refractive index of 1.5522, moisture content of 0.56%, turbidity of 1.79 NTU, pour point of approximately 3°C, and elongation at break of 16.8%. FTIR analysis revealed characteristic aliphatic C–H and aromatic hydrocarbon absorption bands, confirming the hydrocarbon-rich nature of the blend. The 80/20 PS/PE composition was selected as the most promising blend within the investigated range because of its balanced physicochemical and mechanical properties. Further evaluation of paint adhesion, drying time, gloss, opacity, water resistance, storage stability, and environmental safety is recommended before practical application.