Nano-composite Semi-Flexible Polyurethane Foams Containing Montmorillonite Intercalated/exfoliated in Situ During the Synthesis of the Intermediate Polyester-Polyols Obtained from PET Wastes

Low-cost nano-composite semi-flexible polyurethane foams with improved thermal and mechanical features were obtained using a cost-saving and environmentally friendly preparation process of an intermediate com-posite, obtained from polyethyleneterephthalate (PET) wastes, depolymerization/chemical modification agents from renewable resources and unmodified natural montmorillonite. The process implies tailoring the polyester-polyols chemical structure/ composition and using specific catalysts, aiming to intercalate the montmorillonite layers during the synthesis reactions, while maintaining the appropriate properties of the products required for the preparation of polyurethane semi-flexible foams, thus avoiding conventional treatments of the nanofiller, involving the use of solvents, additional energy consumption by heating and stirring, as well as longer processing time. The polyester-polyols composites and the polyurethane semi-flexible foams obtained therefrom were investigated by specific analytical methods. In this regard, the foams showed an improvement of the thermal stability, and values of Young's moduli and compression strengths about double or higher, compared to con-ventional semi-flexible polyurethane foams of same density. The potential applications of such foams target shock wave damping sandwich systems for marine structures.