A Fully Biobased Aromatic Polyester Polyol for Polyisocyanurate Rigid Foams: Poly(diethylene furanoate)

Aromatic polyester polyols are often used in polyurethane rigid foam (PUR) and polyisocyanurate (PIR) synthesis, since they offer higher rigidity than polyether polyols. Herein, a route toward fully biobased aromatic polyester polyols was investigated using sugar-based 2,5-furandicarboxylic acid (FDCA) and diethylene glycol (DEG), enabling a direct one-step synthesis of a fully biobased aromatic polyester polyol, poly(diethylene furanoate) (PDEF), for applications in PIR rigid foam. Therefore, reaction conditions were optimized to obtain PDEF as a processable polyol with OH values and remaining unreacted DEG similar to a commercial, petroleum-based polyol. The processability was improved by either copolymerizing 10–20 mol % of a biobased aliphatic dicarboxylic acid, like succinic acid (SA) or adipic acid (AA), maintaining the fully biobased character of the polyol, or copolymerization with phthalic acid. The fully biobased polyester polyols were successfully prepared on a 100 g scale of dicarboxylic acids. Subsequent application in PIR rigid foam showed similar density, thermal conductivity, flame behavior, and compressive strength if compared to the rigid foam obtained from a commercial polyol. Thus, fully biobased PDEF can substitute petroleum-based aromatic polyester polyols in PIR applications.