Hydrophobic modification of water-borne poly(vinyl alcohol) electrospun nonwovens for advanced applications

Abstract

A new approach for surface modification of hydrophilic and water-soluble polymeric nonwovens has been investigated. Here, the challenge was to prepare a highly water repelling material from a water-based system. This paradox was resolved by a novel concept of coating chemically reactive water soluble polymers with fluorinated silyl ethers, which was probed with poly(vinyl alcohol) (PVA) nanofibers. Key for getting high water repellence was the discovery that PVA had to be preheated to 180°C prior to silanization before coating with a mixture of tetraethyl orthosilicate (TEOS): n-decyltrimethoxysilane (DTMS): ethanol: H2O: HCl. As a result of this surface modification and additional annealing of electrospun PVA nanofibers, highly water repelling nonwovens were obtained which also showed very low roll angles and consequently high dimensional integrity upon contact with water. The nonwovens were characterized by means of thermogravimetric analysis, wide angle x-ray analysis, electron microscopy, capillary flow porometry, contact angle measurement, and energy-dispersive X-ray spectroscopy to gain in-depth insight into the mechanism of the surface transformation.