Effect of Silica Sol-Modified Nano-Calcium Carbonate on Polyurethane(Urea) Dispersions and their Films

A series of novel aqueous polyurethane(urea) (PUU)/silica sol-modified nano-calcium carbonate (CaCO₃) hybrid dispersions were prepared using an in situ dispersion technique. Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) examinations indicated that the modified nano-CaCO₃ particles were mostly covered or partially inlaid on the surface of PUU particles or in the PUU matrix. PUU/modified nano-CaCO₃ hybrid dispersions with lower modified nano-CaCO₃ content (≤15%) exhibited low viscosity, small particle size and excellent stability. The rheological features revealed that this hybrid PUU dispersion belonged to pseudoplastic fluids. In addition, the incorporation of modified nano-CaCO₃ could also enhance the mechanical properties of PUUs dramatically through the reinforcing effect of inorganic CaCO₃. The better water resistance of PUU/modified nano-CaCO₃ hybrid films proved that modified nano-CaCO₃ could be used as effective modifiers for PUUs, and this method provided an efficient way to incorporate silica sol-modified nano-CaCO₃ in the PUU matrix.