High solid and high performance UV cured waterborne polyurethanes

High solid and thermally stable waterborne polyurethanes (WPUs) were designed and synthesized by introducing imide groups into the hard segment and locating the anionic groups at the chain termini (terminal ions). It was found that the terminal ions gave rise to a much finer dispersion, higher dispersion stability and viscosity, whereas the conventional hard ions (those containing ionic groups in the hard segments) produced greater water swelling. Also, the terminal ions lead to a high-solid content (50%) at a low ionic content (2%), due to the effective exposure of the ionic groups to the particle surface, owing to the high mobility of the ionic groups and low free energy of the chain ends. When imide groups replaced urethane groups in the hard segment, remarkably enhanced mechanical, dynamic mechanical properties and thermal stability were obtained.