Improving the Flexibility and Water Resistance of Thermo-Compressed Guar Gum Films by Blending Natural Rubber for Use in Sustainable Packaging Applications

Guar gum (GG), a typical biopolymer, has found widespread use in packaging applications due to its biodegradability, non-toxicity, and low price. However, the further application of GG is significantly limited by its poor flexibility and water resistance. In this study, GG/natural rubber (NR) films were prepared by thermo-compressing hand-kneaded pastes made from GG powder and fresh NR latex. Various NR contents-5, 10, 20, and 40 wt%-were investigated. Water-resistant properties were determined by moisture absorption, water dissolution, surface wettability, and water vapor permeability. Fourier transform infrared spectroscopy indicated interactions between the dispersed NR phases and the GG matrix. Scanning electron microscopy revealed distinct phase separation between the GG and NR phases in the films. All GG/NR films exhibited excellent interfacial adhesion between GG and NR phases. Tensile results indicated that an increase in the amount of NR in the GG-based films led to a decrease in both maximum tensile strength and Young's modulus, while elongation at break increased. GG/40% NR films exhibited an elongation at break of 17.5%, which is a substantial increase of 415% compared to pure GG films. The addition of NR showed improved water-resistant properties of GG-based films; however, the rate of biodegradation during soil burial decreased as the NR ratios increased. These thermo-compressed GG/NR blends hold promise as sustainable alternatives to single-use plastic packaging applications.