Regular Aligned Porous Waterborne Polyurethane Composite Obtained by a Directional Freeze-Drying Process

Abstract

Regular aligned porous waterborne polyurethane (WPU) composites were simply obtained by a directional freeze-drying process in the study. The morphology of the WPU composite can be tailored with different concentration of the WPU dispersion and freezing rate. Very regular aligned pores along the immersion direction can be obtained when the concentration of WPU dispersion is 20 wt.%. In addition, the periodicity of the aligned pores can be tuned by the freezing rate such as the temperature of cryogenic liquid or immersing velocity. The periodicity of the aligned pores increases when the immersed velocity decreases and the temperature of the cryogenic liquid increases. With the theory of Mullins-Sekerka, the periodicity of the aligned pores can be accurately calculated.