Abstract

Oxygen plasma treatment was employed to modify polyurethane (PU) leather coating for enhancing water vapour permeability (WVP). Surface morphology, surface chemical composition and surface hydrophilicity of the treated coating were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle/surface energy/equilibrium water sorption analysis respectively. SEM micrographs showed that oxygen plasma treatment did not destroy the integrality of the PU leather coating. XPS results further indicated that extra oxygen-based polar groups (-C-O- and -C=O) were implanted into the coating surface after plasma treatment. As a result, the surface hydrophilicity of the treated coating was improved, which was demonstrated by decreased contact angle, increased surface energy and increased equilibrium water sorption. Due to the improved surface hydrophilicity, theWVP of the PU leather coating was found to increase with increasing plasma treatment time. When the plasma treatment lasted for 120s, maximum WVP increases from 611g/m2.day to 889g/m2.day for PU films, from 324g/m2.day to 441g/m2.day for finished split leather and from 112g/m2.day to 157g/m2.day for synthetic leather were observed respectively. Simultaneously, crucial mechanical properties of the PU leather coating, such as tensile strength, elongation at break and elasticity modulus were not sacrificed by the plasma treatment.