Characterization and application of composite resin of natural rubber latex and polystyrene waste as a binder for water-resistant emulsion paint formulation

Sustainable production of efficient and low-cost coating materials from recycled plastic wastes will have a significant impact on economic advancements in paints and coatings, as well as waste management. Polystyrene waste was reduced to a resin, which was further modified by blending with natural rubber latex (NRL). The recycled polystyrene resin (rPS) and NRL formed homogeneous composite resins (rPS-NRL) blends in various ratios, and the changes in some physicochemical properties of the resins were studied. The rPS-NRL blended in different ratios exhibited higher density (0.83–0.92 g/cm3), refractive index (1.401–1.438), viscosity (935–1287 cP), elongation (5–18 %), and melting point (184°C–217.5°C), as well as lower moisture uptake (1.1–0.88 %) and faster drying time (32–19 min), compared to the rPS resin. Changes in functional, structural, and morphological characteristics of the resins were studied using Fourier transformed infrared (FTIR) spectrometer, X-ray diffractometer (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TGA-DTA). The results indicated molecular interactions between NRL and the rPS resin, which form the basis for the unique physicochemical properties of the composite resin compared with the pristine rPS and NRL resins. White (CaCO3) pigmented emulsion paint produced using the rPS-NRL composite resin as binder was tested in comparison with paint produced using the conventional polyvinyl acetate (PVA) binder, where the rPS-NRL paint exhibits superior properties, including outstanding resistance to water.