Closed-loop recycling of automotive semi-rigid polyurethane foam using renewable coconut oil

Abstract

The automotive sector represents one of the major application fields for polyurethane (PUR) materials, but their end-of-life management still remains a significant sustainability challenge. This study presents a closed-loop recycling approach for semi-rigid PUR foams employed as interior acoustic insulation in automotive headliners. A bio-based transesterified coconut oil was utilized as a sustainable solvolysis reagent to depolymerize automotive PUR waste and recover recycled polyol. The regenerated recycled polyol exhibited suitable hydroxyl value and viscosity, allowing direct substitution of up to 40 wt% of standard polyol in industrial formulations of semi-rigid PUR foam. The PUR foam with incorporated recycled polyol exhibited good structural integrity, sufficient stiffness due to the presence of aromatic structures, along with balanced flexibility derived from glyceride chain segments, thereby avoiding brittleness. The laboratory-scale formulation was successfully scaled up for the production of an industrial headliner demonstrator, confirming the practical feasibility of recycled polyol use in real manufacturing conditions. This work highlights a circular and sustainable strategy for PUR-based automotive components, reducing dependence on petrochemical feedstocks and mitigating environmental impacts.