Polyurethanes derived from aromatic polyesters exhibit excellent hydrolysis resistance, heat resistance, and adhesion. Phthalic anhydride-based polyester polyols and aromatic polyester polyols produced from waste polyester (PET) or waste PTA are commonly used to manufacture rigid polyurethane foams. Rigid foams based on high-hydroxyl-value aromatic polyester polyols demonstrate superior flame retardancy compared to those based on polyether polyols. In the polyurethane foam industry, aromatic polyester polyols are frequently used to replace some or all of the polyether polyols in formulations for rigid polyurethane and polyisocyanurate (PIR) foams. Incorporating a portion of aromatic polyester polyol into formulations for refrigerator foam systems used in winter can also enhance the foam's toughness and adhesion.
Phthalic anhydride-based polyester polyols are particularly well-suited for polyisocyanurate (PIR) foams; the high content of benzene rings in the foam matrix enhances heat resistance while simultaneously improving flame retardancy. Aromatic polyester polyols are widely used both domestically and internationally for the production of sandwich foam panels for construction and for on-site spray application in the building industry. In addition to possessing the fundamental properties of polyether-based rigid polyurethane foams, these polyester-containing rigid foams offer advantages such as fine cell structure, good toughness, excellent flame retardancy, and low cost. Polyester polyols contain a high concentration of primary hydroxyl groups, resulting in high reactivity; this allows for low-temperature application and reduces the required amount of catalyst. Specific applications within the rigid foam industry include rigid foam boards and sandwich panels; foam systems for the insulation of refrigerators, freezers, and water heaters; spray-applied rigid foam; imitation wood; single-component rigid foam; ultra-low-density packaging foam; and rigid microcellular shoe sole materials.
