Nonisocyanate Polyurethanes Modified by Polysiloxane with Good Mechanical Properties and Hydrophobicity

Polyurethane (PU) has developed rapidly, and it has become an irreplaceable polymer material. Nonisocyanate PUs (NIPUs) have become the focus of research due to the green synthesis route that does not use toxic isocyanates. However, NIPUs face great challenges such as poor mechanical properties, heat resistance, and lack of functions, which greatly limit their applications. In order to enhance the heat resistance and endow functionality of NIPUs, a series of PUs (PCUPs) were synthesized in this paper by melt polycondensation reaction using dimethyl carbonate, 1,6-hexanediol, 1,6-hexanediamine, and nontoxic polydimethylsiloxane (PDMS) as raw materials. The thermal, mechanical properties, water absorption, and anti-graffiti resistance of PCUPs were studied. The experimental results showed that the thermal, mechanical, and graffiti resistance properties of PCUPs were improved by adjusting the content of PDMS. The synthesized PCUPs had excellent mechanical properties with a tensile strength of 38 MPa and an elongation at break of 240% due to the formation of microphase-separated structures promoted by PDMS. After three times of hot compression molding, it still maintains good mechanical properties (87%). In addition, the heat deflection temperature of PCUPs increased from 40.3 to 65.2 °C. Surprisingly, the water contact angle of the PCUP film was 104.7°, showing excellent hydrophobicity and satisfactory graffiti resistance behavior. This study provides a perspective on the functional design of environmentally friendly nonisocyanate polyurethanes.