Influence of Functionality and Aromatic Content of Polyester Polyol on Rigid Polyurethane Foam Properties

Understanding the effects of functionality and aromatic content in polyester polyols (Pespols) is critical for optimizing the performance of rigid polyurethane (PUR) foams. In this study, Pespols were synthesized using phthalic anhydride, adipic acid, glycerol, and diethylene glycol in varying ratios to systematically modify their functionality and aromaticity. The polyols were characterized by acid value, hydroxyl value, and viscosity. Their influence on PUR foams was evaluated through cup tests, compressive strength, density measurements, and SEM analysis. Results demonstrated that higher functionality improved mechanical strength, while increased viscosity negatively affected cell morphology. Aromatic-rich Pespols enhanced compressive properties with minimal effect on cell size. Several of the synthesized formulations exhibited higher compressive strength and similar or lower apparent density compared to commercial Pespol-based foams. These findings highlighted the importance of balancing viscosity, reactivity, and structural integrity, and indicate that tailored Pespol formulations can serve as viable alternatives to polyether polyols, promoting more cost-effective and sustainable PUR foam production.