Waterborne polyurethane/graphene oxide-silica nanocomposites with improved mechanical and thermal properties for leather coatings using screen printing

Waterborne polyurethane (WPU) has been broadly used as adhesive and coating materials in many applications. In this work, the graphene oxide-silica (GOSI) nanocomposites, used as nanofillers in the WPU matrix, were produced by functionalizing graphene oxide with epoxy groups and nanosilica with amine groups using silane terminated coupling agents. The nanocomposite surface structures were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The polymer nanocomposite films show the excellent improvement in the mechanical and thermal properties. In the fractured surface study of the composite films by SEM, it was observed that the agglomeration of GO appears while the GOSI is uniformly distributed in the WPU matrix. Furthermore, the WPU/GOSI have regained the maximum tensile strength properties after two weeks of hydrolysis. The GOSI nanocomposites have enhanced interfacial crosslinking with the WPU matrix which is the prime reason for such development in the mechanical properties. The screen printing method was illustrated to cast the thin and transparent layer WPU nanocomposites on the leather surfaces. The WPU/GOSI coatings exhibit outstanding tear resistance, surface adhesiveness, and abrasion resistance properties. This approach of using GOSI composites as nanofiller in the polymer matrix may pave a novel path for surface coating strategies.