Optimization of Expanded Polystyrene Waste Dissolution Using Citrus Essential Oil for the Development of Sustainable Polymeric Coatings

The growing demand for sustainable alternatives to plastic waste management has driven interest in the upcycling of expanded polystyrene (EPS) using bio‐based solvents. This study proposes a green method for dissolving EPS waste in orange essential oil (OEO), a citrus‐derived solvent rich in limonene, to develop functional polymeric coatings. The core objective was to optimize the formulation parameters—namely, the concentrations of EPS and OEO—to enhance the coatings' performance. Response surface methodology (RSM) was employed to model the influence of these variables on density, contact angle, viscosity, water vapor transmission rate (WVT), and minimum film formation temperature (MFFT). The analysis enabled the identification of an optimal formulation containing 1.02 g of EPS, and a 5.00 mL of OEO that maximized hydrophobicity while maintaining favorable film characteristics. The results demonstrate the viability of this strategy as a sustainable upcycling method, contributing to circular economic efforts by valorizing both plastic and agricultural waste. This work highlights the potential of green solvents and statistical optimization as key tools in the development of environmentally conscious polymeric materials.