An environmentally friendly preparation and characterization of waterborne polyurethane hydrogels by polyvinyl alcohol physical cross-linking to improve water absorption

Abstract

In this study, waterborne polyurethane hydrogels were successfully synthesized with a waterborne polyurethane solution (WPU) and poly(vinyl alcohol) (PVA), which acted as a cross-linking agent in a freezing–thawing method. The average diameter of WPU, as determined by dynamic light scattering, was around 41.3 nm. The structure and morphology of the polyurethane composite hydrogel were characterized by means of FTIR, SEM and TGA, which confirmed that WPU and PVA formed a homogeneous miscible system through hydrogen bonds. The FTIR analysis showed that with the increasing WPU content, a large number of hydroxyl groups were provided for hydrogen bonding with the carbonyl group of WPU, resulting in strong hydrogen bonding interactions. From SEM, the number of surface pores of the PU/PVA composite hydrogels increased with increasing WPU content. With the increasing WPU content, the tensile strength of the PU/PVA composite hydrogels decreased. 70% PU/PVA prepared gave the best water absorption of 16.33 g g⁻¹ in distilled water. The PU/PVA hydrogels had three stages of water absorption, namely, a fast adsorption phase, a slow adsorption phase and an equilibrium adsorption phase. The waterborne polyurethane hydrogel prepared from an environmentally friendly synthetic method was shown to be a promising new candidate as a wound dressing material.