Physicochemical Properties of Amino–Silane-Terminated Vegetable Oil-Based Waterborne Polyurethane Nanocomposites

A series of biobased polyurethane–siloxane cross-linked coatings were prepared using castor oil, partially biobased Tolonate, and 3-aminopropyl trimethoxysilane. The 29Si NMR spectra was used to determine the formation of cross-linking structure of the polyurethane–siloxane system. FT-IR studies verified that a hydrogen bonding interaction existed at the interface of the castor oil-based polyurethane–siloxane moieties, thereby shifting the characteristic peak position of N–H and C═O groups to higher field values. The curing process of the dispersions was followed by means of gel content measurements. The thermal properties of neat waterborne polyurethane and its nanocomposite films were tested by thermogravimetric analysis and differential scanning calorimetric. TGA tests proved that adding silica nanoparticles increased the thermal stability of the nanocomposites. DSC measurements showed that the addition of silica nanoparticles increased the glass transition temperature. Silica nanoparticles in the polyurethane matrix had a significant influence on mechanical properties: The charging level increased from 0% to 5%, and the Young's modulus and tensile strength of the polyurethane nanocomposites increased from 26.3 to 109.3 and 13.4 to 25.9 MPa, respectively. Atomic force microscopy was also used to represent the surface topography of the polyurethane–siloxane films. The surface wettability and rheological properties of the films were also evaluated. The overall performance of coatings revealed that biorenewable-based polyurethane–siloxane can be successfully used as coatings in various applications.