Novel waterborne poly(urethane‐urea)/silica nanocomposites

Abstract

AbstractA series of novel transparent mechanically strong waterborne poly(urethane‐urea)/silica nanocomposites were prepared by mixing a waterborne poly(urethane‐urea) dispersion with aqueous nanosilica, followed by slow water evaporation. This procedure is simple, environmentally friendly and energetically undemanding. The silica content in the nanocomposite film varied from 0 to 50 wt%. Based on changes of tensile characteristics, for example, Young's modulus values, three types of behavior were observed: typical elastic (0‐10 wt%), plastic (30 wt%) and ceramic‐like (50 wt% silica) materials can be prepared. However, some films feature both elastic and plastic (material with 20 wt% silica) or plastic and ceramic‐like characteristics (material with 40 wt% silica). The Young's modulus varied from 6 to 705 MPa, and the maximal tensile strength and elongation‐at‐break were 17.3 MPa and 1270%, respectively. The maximum energy‐to‐break, 60 mJ mm−3, was achieved for the film containing 30 wt% silica. All these materials can potentially be used as soft‐to‐hard topcoats, depending on the specific demands.