Modification of cassava starch using aqueous NaOH-urea solution for development and evaluation of an eco-friendly...

The research aimed to develop improved bioadhesives from cassava starch by utilizing a specialized NaOH-urea solution to address issues with conventional starch adhesives, including excessive thickness, low solid content, weak bonding strength, and instability due to retrogradation. Cassava starch was extracted through wet milling and incorporated into the adhesive formulation at 1-9 %. The method produced starch granules that are less damaged, with decreased peak viscosity and swelling properties. The bio-adhesives were created using a cold gelatinization process. The process requires less energy, preventing thermal degradation, controlling viscosity, and reducing retrogradation. The properties of the starch were studied using various techniques, including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), as well as tests for swelling and solubility. The findings indicated that the extracted starch had a moisture level of 8.00 %, a pH of 5.97, and comprised 24.95 % amylose and 75.05 % amylopectin. Increasing the starch content enhances the viscosity (1110 cP), solid content (14 %), and tensile strength (both in wet and dry conditions), as well as the adhesive's internal bonding, while also decreasing the gel time (271 s), making it more suitable for wood-based composites. XRD and FTIR analyses validated the morphological alterations caused by the NaOH-urea treatment. The starch-based adhesive (9 % SBA) exhibited superior performance. This study demonstrated the first systematic implementation of the cold gelatinization process, specifically applied to cassava starch for use in wood adhesives.