Synthesis and characterization of polyurethane foams from waste cooking oil (WCO)

Polyurethanes represent one of the most versatile families of polymers, enabling applications that range from flexible cushioning materials to rigid thermal insulation, coatings, and adhesives. Their production is generally based on the polyaddition reaction between polyols and polyisocyanates1. Growing environmental awareness and the need to reduce petrochemical reliance have made renewable polyol sources a key research priority. In this study, waste cooking oil (WCO) was employed as a sustainable and widely available raw material for the preparation of bio-based polyols. With global WCO generation reaching 41–52 million tons annually2, its valorization represents a promising route toward circular, low-impact polymer production. The polyol was produced from waste cooking oil via glycerolysis at 225 °C for 2 hours using NaOH as catalyst, then purified to remove excess glycerol and catalyst. 1H NMR confirmed a polyol-rich mixture (67% monoglycerides, 30% diglycerides, 3% triglycerides). The resulting bio-polyol was reacted with a 68% bio-based aliphatic isocyanate (Desmodur® CQ N7300) in a closed mold, together with commercial catalysts, surfactants, and water as blowing agent, to obtain polyurethane foams. Different formulations were tested by varying the NCO/OH ratio. The resulting materials were analysed through infrared spectroscopy (IR) and scanning electron microscopy (SEM) to investigate their chemical structure and cellular morphology. Thermal stability was assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Density measurements and mechanical tests were conducted to classify the foams and distinguish rigid, semi-rigid, and flexible types.