Compatible compositions based on aqueous polyurethane dispersions and sodium alginate

► The alginate content was studied on properties of aqueous polyurethane dispersions. ► Excellent miscibility was shown on the compositions of polyurethane and alginate. ► The morphology of alginate in polyurethane matrix was shown as particulate with different sizes. ► The presence of alginate in microstructure was determined by sodium peak in EDX. A series of aqueous polyurethane dispersions were synthesized by the reaction of polytetramethylene glycol and isophorone diisocyanate, extended with dimethylol propionic acid. Their chemical structures were characterized using FTIR, 1H NMR, and 13C NMR, and thermal properties were determined by DMTA. Then, a number of aqueous polyurethane dispersions–sodium alginate (PUD/SA) compositions were prepared by addition of sodium alginate solution with different concentrations into the aqueous polyurethane dispersion. Characterization of chemical structure and thermal properties of these blends were performed by FTIR, EDX and DMTA, respectively. The morphology of the alginate in polyurethane matrix was studied by SEM. The hydrophilicity of the prepared samples decreases by increasing the content of sodium alginate in blends. These observations were attributed to the increase of hydrophilicity of the blends as a consequence of addition of hydrophilic carboxylate, hydroxyl and ether functional groups of the alginate to them.