Hydrophobicity enhancement of the polyvinyl alcohol/rice starch/silk fibroin films by glycerol

Abstract

Eco-friendly films have been prepared using various biopolymers and their properties have been improved in order to meet the requirements for appropriate applications. However, the frequently encountered weakness of the properties of most biopolymer film is its water solubility. In this study, the polyvinyl alcohol/rice starch/silk fibroin (PVA/RS/SF) films were modified by the addition of glycerol aiming to increase the hydrophobicity of the films. Some properties of the modified films including water contact angle, degree of swelling and water solubility were compared with the unmodified PVA/RS/SF film. Results from the contact angle measurement showed that the films with glycerol could be transformed to be hydrophobic after soaking in ethanol medium. The increase in soaking time tends to increase the hydrophobicity of the films. However, at about 60 min soaking, the water contact angles on the films were quite constant with the values of about 107.9±5.2° comparing with 65.3±2.4° of the ethanol-untreated PVA/RS/SF films. In addition, the ethanol-treated glycerol-modified films also show higher degree of swelling with constant solubility and better mechanical properties. © (2014) Trans Tech Publications, Switzerland.