Influence of tannin from Indian almond leaves on the curing behavior of Sucrose-Citric acid adhesive

The development of an eco-friendly wood adhesive composed of renewable materials has become a major topic of wood-based panel industry due to their safety for human health and potential use for particleboard production. Formaldehyde-based wood adhesive can emit formaldehyde which poses as a threat to the indoor air quality. Therefore, several researchers used sucrose, citric acid, and tannin as raw materials for the synthesis of eco-friendly adhesives, since these compounds showed a great synergy effect when used as a wood adhesive. A synthesized Citric-Sucrose-Tannin (CST) adhesives was studied in this work. Tannin, extracted from Indian almond leaves, was added into the 40 wt% of dry sucrose and citric acid in order to increase adhesion efficiency. To form the particleboard hot press is needed, each sample is pressed at temperature of 160 °C for three consecutive steps; four MPa for two minutes, two MPa for two minutes, and one MPa for two minutes. It was found that the optimized proportion of sucrose:citric:tannin in adhesive was 75/25/25 as it gave the particleboard the highest Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) values. Compared to non-adhesive particleboard, the MOR and MOE values were improved by two and four times when this formaldehyde-free adhesive was applied. It can be concluded that the eco-friendly wood adhesive composed of citric, sucrose, and tannin extracted from Indian almond leaves significantly enhanced both the mechanical and physical properties of particleboard.