Synthesis and properties of castor oil-based waterborne polyurethane/sodium alginate composites with tunable properties

In this paper, bio-based waterborne polyurethane dispersions were successfully prepared from castor oil using 2, 2-dimethylolbutanoic acid as the chain extender. Then, a series of bio-based composite dispersions and films were prepared by blending different amounts of sodium alginate aqueous solution with these bio-based polyurethane dispersions. The chemical structures, thermo-mechanical properties, thermal stability, and mechanical properties of the resulting composite films were characterized and discussed. The results show that the tensile strength and storage moduli of the composite films increase while the elongation at break of the composite films decrease with increasing the sodium alginate content. In addition, the contact angle and thermal stability of the composite films also increase with increasing sodium alginate content. These improvements are related to the increase of the crosslink density and the formation of interpenetrating networks with introduction of sodium alginate macromolecule.