Influence of urea and glycerol on functional properties of biodegradable PVA/xylan composite films

In recent years, numerous studies have focused on biodegradable plastics for agricultural applications. To improve the mechanical and hydrophobic properties, biodegradable xylan composite films containing poly(vinyl alcohol) (PVA) were successfully prepared by casting method in this work. A series of composite films at a PVA/xylan weight ratio of 3:1 under the addition of glycerol and urea were investigated. Influences of the urea and glycerol amounts on the functional properties of composite films such as hydrophilicity/hydrophobicity, water vapor permeability (WVP), mechanical properties, solubility and degradability were comparatively investigated. Results showed that increasing the glycerol amount led to a decrease in tensile strength and an increase in elongation at break and WVP, while the addition of 1 % urea in composite films without glycerol had a positive impact on improving the water resistance of composite films; the contact angle and WVP values reached 114.68° and 4.11 × 10^?11 g m^?1 s^?1 Pa^?1. Moreover, thermogravimetric analysis, FTIR and a scanning electron microscope were used to confirm the compatibility of the PVA and xylan components. FTIR analysis displayed the intensity of hydroxyl groups of films became stronger with increasing amounts of glycerol, while the opposite results were obtained with an increase of the amount of urea. These indicated that glycerol could improve the miscibility between PVA and xylan, and the addition of urea could enhance the water resistance of composite films.