Chemical Recycling of Polyurethane Waste via a Microwave-Assisted Glycolysis Process

In this work, we explored a microwave-assisted glycolysis process to chemically recycle rigid polyurethane (PU) foam waste to obtain a single-phase product with suitable physio-chemical properties as a secondary raw material for the preparation of new rigid PU products. Such an approach was compared to a conventionally heated (ConvH) process, analyzing the performances of different catalysts. The use of microwaves allowed a 94% decrease in the reaction time scale of rigid PU depolymerization, with a concurrent 45% reduction in energy expense. By using a PU/diethylene glycol mass ratio of 1.5, best performances were obtained with a 30 mmol/100g_PU potassium acetate concentration, both in terms of the product viscosity and aromatic amine byproduct content. The glycolysis products recovered were employed in substitution to virgin polyol for rigid PU foam preparation, showing improved compressive strength and comparable thermal insulation properties up to a 30% content with respect to the traditional non-recycled counterpart.