Sustainable adhesive from waste expanded polystyrene: Performance governed by solvent-substrate interplay

This study presents a sustainable approach for converting post‑consumer Expanded Polystyrene (EPS) into a high‑performance adhesive. EPS was dissolved in various organic solvents and modified with PMMA, and the resulting formulations were evaluated chemically, Rheologically, and mechanically. Solubility trends correlated with Hansen Solubility Parameters, with toluene showing the highest dissolution efficiency (RED = 0.65). Rheological analysis revealed near‑Newtonian to mildly shear‑thinning behavior (STI = 0.018-0.203), indicating viscosity stability suitable for application. Mechanical testing demonstrated strong substrate‑dependent performance: xylene‑based adhesives achieved high bonding strength on non‑polar leather (≈ 778 KPa), while MEK‑based formulations exhibited superior adhesion to wood (≈ 755 KPa) due to enhanced hydrogen bonding. Incorporation of PMMA further reinforced the adhesive network, yielding the highest tensile strength (≈ 1969 KPa). All formulations bonded effectively to polyurethane and showed robust qualitative adhesion to ceramic. These findings validate the feasibility of upcycling EPS waste into a versatile, high‑strength adhesive, offering a practical and environmentally beneficial solution for plastic waste management.