Two-component waterborne polyurethane modified with terpene derivative-based polysiloxane for coatings via a thiol-ene click reaction

Waterborne polyurethane has gradually become a focus among researchers due to its low volatile organic emissions and low pollution. However, some problems exist with waterborne polyurethane, such as poor mechanical properties, obvious hydrophilicity and poor heat resistance. Herein, a terpene-modified polysiloxane-based polyurethane was designed to solve the abovementioned problems. 3-Mercaptopropylmethyldimethoxysilane and octamethylcyclotetrasiloxane were used as raw materials to prepare hydroxyl-terminated polysiloxane (PMMS). As a derivative of camphene, biomass resources, isobornyl acrylate was grafted to the prepared polysiloxane side chain through the thiol-ene click reaction under ultraviolet light irradiation conditions. Terpene-based polysiloxane (PMMS-I) was used as one of the polyol components to modify two-component waterborne polyurethane. Due to the combination of low surface energy polysiloxane and a hydrophobic terpene derivative, the hydrophobicity of the modified waterborne polyurethane was significantly improved, where the static water contact angle was increased from 70.7 ° to 101.2 ° and the water absorption was reduced from 16.0% to 6.9%. In addition, because of the unique rigidity of the terpene ring, the tensile strength of the modified polyurethane was significantly improved from 4.70 MPa to 8.82 MPa. In addition, the thermogravimetric analysis results showed that the thermal stability of the modified polyurethane was ameliorated. In terms of improving the properties of polymer materials, terpene bio-based compounds have broad potential.