Aqueous anionic polyurethane dispersions from castor oil

In this study, dimethylol propionic acid (DMPA) and dimethylol butanoic acid (DMBA) were employed to synthesize the castor oil-based waterborne polyurethane dispersions (PUDs). The effects of these two emulsifier and their contents on the properties of the PUDs as well as their films were investigated systematically. The results show that as the emulsifiers contents increase, the particle size and zeta potential of the PUDs decrease while the tensile strength of the resulting PU films increase but thermal stability, water and chemical resistance decrease. The PUDs from DMBA exhibit smaller particle size than those from DMPA and the films from the former show higher tensile strength, higher elongation at break but lower thermal stability, lower water resistance. This work provides a new way to synthesize environmental friendly bio-based waterborne polyurethanes whose properties can be tuned according to their application, such as coating, ink, leather, styling products and so on.