Improving the property of castor oil-based waterborne polyurethane by polyhydroxy sapium sebiferum oil as crosslinking agent

In this paper, the sapium sebiferum oil-based polyols (SOP) were prepared by thiol-ene photo-click reaction with mercaptoethanol and inedible sapium sebiferum oil with high iodine value. The molecular structure and hydroxyl values of the SOPs were determined. Then, modified castor oil based waterborne polyurethane was prepared by using SOP, castor oil and isocyanate as raw materials. The particle size and the chemical structure of the emulsions were characterized. Anti-graffiti properties, water contact angle, mechanical properties and thermal properties of the films were tested. When the mass ratio of the SOP to castor oil increased, the water contact angle of the modified film increased by nearly 20°, and it showed good anti-graffiti performance, which can be erased by dry bumf without leaving trace after being written by marker. In addition, the temperature of 50% weight loss of modified film increased by 12 °C and the tensile strength and elongation at break can be improved 2.2 and 2.8 times than before, respectively, which may be related to the addition of crosslinking in the polyurethane by polyhydroxy SOP.