Polyurethane foam from waste cooking oil (WCO)

Polyurethanes are a fundamental class of polymer, widely used in a variety of everyday applications such as mattress and seat padding (flexible foams), thermal insulation (rigid foams), paints, and adhesives. Their very high versatility is correlated with the possibility of tuning polymer’s final feature during the synthetic process. They are traditionally synthesized via the polyaddition reaction between a polyisocyanate and a polyol [1]. In the present study, the polyol component was successfully obtained through the glycerolysis reaction of pretreated waste cooking oil (WCO). WCO is identified as an alternative renewable feedstock of significant strategic interest, attributed to its wide availability. Considering recent estimates that place global annual production between 41 and 52 million tons, WCO is established as a critical resource for advancing sustainable material development [2]. In this work WCO was first anhydrified and filtered to remove water and solid impurities, then it was reacted with glycerol under an inert nitrogen atmosphere using sodium hydroxide (NaOH) as the basic catalyst. The reaction was conducted at 225 °C for 2 hours. Afterwards, glycerol and catalyst were removed, and the resulting glyceride mixture was analysed using 1H-NMR spectroscopy. The compositional analysis confirmed the successful transformation, revealing a product mixture consisting of 67% monoglycerides, 30% diglycerides and 3% triglycerides. Rigid polyurethane foams (RPUFs) were subsequently produced by reacting the synthesized glyceride mixture (PO) with a 68% bio-based aliphatic isocyanate (Desmodur®CQ N7300) along with commercially foaming and gelling additives and a surfactant. Distilled water was also used as the chemical blowing agent and the foaming process was carried out in a mold. The obtained RPUFs were characterized by infrared spectroscopy (IR), as well as scanning electron microscopy (SEM) and optical microscopy to investigate their morphology. Thermal behaviour, crucial for long-term stability in applications such as insulation, has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). This approach demonstrates a viable pathway for the high-value valorization of WCO, yielding a high-performance material with a significantly reduced petrochemical footprint.