Nano-composite semi-flexible polyurethane foams containing montmorillonite intercalated/exfoliated in situ during the synthesis of the intermediate polyester-polyols obtained from PET wastes

[Display omitted] •Developing semi-flexible polyurethane foams based on montmorillonite.•Tailoring the structure and composition of polyester-polyols derived from PET.•Preparing polyurethane composite foams as components for ship embroidery.•Improved compression strengths compared to other semi-flexible polyurethane foams.•Values of Young’s moduli double compared to conventional foams of same density. 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 composite, 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 conventional semi-flexible polyurethane foams of same density. The potential applications of such foams target shock wave damping sandwich systems for marine structures.