Synthesis and properties of crosslinked waterborne polyurethane

Waterborne polyurethane prepolymer was prepared by the reaction of isophorone isocyanate(IPDI), polyether polyol(PTMG), dimethylol propionic acid(DMPA) and trimethylol propane(TMP), which was modified by silicane coupling agent(APTES) to form highly crosslinked polyurethane emulsion. The films of the waterborne polyurethane were prepared. The structure of the polyurethane was characterized by Fourier transform infared spectrometer (FTIR), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mechanical properties and water absorption of the films were measured. FT-IR indicates that APTES reacted with -NCO of polyurethane. XRD and DSC shows that crystallinity of polyurethane decreased with the increase of w(APTES). Tensile strength increases as the NCO/OH ratio increases. Tensile strength of films increases with increase of w(DMPA) and elongation at break decreases. The water absorption decreases with the increase of w(TMP) when w(TMP) is lower than 1.8%. As the mass fraction of APTES increases from 0% to 10%, the tensile strength of PU films increased from 18 MPa to 28 MPa, water absorption and ethanol absorption decreased.