Asynchronous synthesis method of waterborne polyurethane with the differences of structural features and thermal conductivity

Waterborne polyurethane (WPU) was successfully synthesized with two ways of one-step method and two-step method, mainly focusing on the effects of asynchronous synthesis method on WPU films’ structural features and thermal conductivity. Compared to the one-step synthesis method of WPU (OS-WPU), the two-step synthesis method of WPU (TS-WPU) showed a high thermal conductivity and approximately 1.4-fold higher than OS-WPU. In addition to this, the water- and solvent-resistance properties and crystallinity of TS-WPU also displayed a better performance than that of OS-WPU. Instrumental analyses of FTIR, DSC, DMA, AFM, SEM and XRD indicated that TS-WPU had an evenly phase separation and lots of microcrystal domains, which is owing to the more ordered structures existed in hard and soft segment domains. In short, the long-range order, short-range order and microcrystal domains existed in WPU can facilitate the phonon propagation, and that is corresponding to the increasing of thermal conductivity.