Innovatove Eco-Friendly Wood Adhesive Formulations: Exploring the Efficacy of Gelatinized Cassava Starch and Polyvinyl Alcohol Crosslinked with Citric Acid

In an effort to develop eco-friendly bio-adhesives for wood applications, this study explores the effect of citric acid as a new cross-linking agent on the properties of a cassava starch/polyvinyl alcohol (PVA)-based wood bio-adhesive. The bio-adhesive was synthesized in a three-step process: first, the hydrolysis of cassava starch using hydrochloric acid, followed by the oxidation of cassava starch with ammonium persulfate, and finally, the polymerization of starch and PVA with citric acid. The reaction was conducted for 100 min in a three-neck flask, using a mercury stirrer at 70°C under atmospheric pressure. The amount of citric acid added to the adhesive was calculated based on the dry weight of the cassava starch, with percentages ranging from 0%, 0.5%, 1%, 1.5%, to 2%. The adhesive characteristics were then evaluated in line with the ASTM D906 wood adhesive standard. Tests were conducted to measure adhesive viscosity, solid content, dry and wet shear strengths, thermal stability, and surface morphology. Molecular changes resulting from the addition of citric acid were analyzed using Fourier transform infrared spectroscopy. This research demonstrated that the addition of citric acid improved the adhesive properties. Specifically, the addition of 2% citric acid (AD-CA2.0) produced optimal results across several analyses. These included a high viscosity reading of 2910 cP, dry and wet shear strengths of 1.21 MPa and 0.89 MPa, respectively, and high solid content of 36%. (author)