High bio-content castor oil based waterborne polyurethane/sodium lignosulfonate composites for environmental friendly UV absorption application

In this work, a series of castor oil-based waterborne polyurethane composites were prepared with different amounts of sodium lignosulfonate as functional filler. The effect of the sodium lignosulfonate contents on the particle size and storage stability of the polyurethane composite dispersions was studied and discussed. In addition, the thermo-mechanical, thermal stability, mechanical properties and UV absorption of the resulting polyurethane films were characterized. The composite dispersion exhibits excellent storage stability and the bio-content of the resulting composite films is high up to 70%. In addition, it was found that the tensile strength and storage modulus increased with increasing the sodium lignosulfonate contents due to enhancement effect from the rigid benzene ring structure of sodium lignosulfonate and good compatibility between polyurethane matrix and the filler. The introduction of sodium lignosulfonate into WPU matrix rendered the excellent UV absorption of the composites due to the conjugated structures of lignin macromolecular. This work provides a new simple method to prepare environmental friendly bio-based waterborne polyurethane composites, which could find widely application in the field of UV absorption coatings and sunscreen cream.