1. Jovana Savić, Šumarski fakultet Beograd, Serbia
2. Milica Rančić, Šumarski fakultet Beograd, Serbia
3. Mladjan Popovic, Šumarski fakultet Beograd, Serbia
4. Ivana Gavrilovic-Grmusa, Šumarski fakultet Beograd, Serbia
Wood adhesives play a crucial role in the production of solid wood products and wood-based materials, as the quality of the adhesive bond directly affects the strength, durability, and reliability of the final product. Growing environmental and health concerns associated with conventional formaldehyde-based adhesives have increased interest in bio-based adhesives derived from renewable, biodegradable, and non-toxic raw materials. Starch is a promising material for this purpose; however, its pronounced hydrophilicity limits the moisture resistance of starch-based adhesive bonds. This study investigated the modification of a commercial starch adhesive with citric acid to improve the moisture resistance and mechanical properties of bonded wood joints. Beech (Fagus sylvatica L.) specimens were bonded using an unmodified starch adhesive and formulations containing 10%, 20%, and 30% citric acid relative to the dry starch mass. Because the specimens pressed at 120 °C disintegrated during conditioning and water exposure, indicating inadequate curing and poor moisture resistance, the pressing temperature was increased to 170 °C, with a pressing time of 10 min and a specific pressure of 1.5 MPa. The specimens were conditioned and exposed to water in accordance with SRPS EN 204:2016 requirements, while tensile shear strength was determined according to SRPS EN 205:2016. The control formulation exhibited the highest mean shear strength of 5.69 MPa, whereas the adhesives containing 10%, 20%, and 30% citric acid achieved mean values of 5.30, 5.33, and 5.33 MPa, respectively. Although citric acid caused a slight reduction in shear strength compared with the control, pressing at 170 °C considerably improved the integrity and moisture resistance of the bonded specimens, which remained intact after water exposure, unlike those pressed at 120 °C. The results demonstrate that pressing temperature is a critical factor in the performance of starch–citric acid bioadhesives because it affects the balance between starch esterification and acid hydrolysis. Further optimization of the adhesive formulation, pressing temperature, pressing time, and catalyst use is required to enhance both moisture resistance and mechanical performance.
Ključne reči :
Tematska oblast:
SIMPOZIJUM D - Ekološki održivi materijali
Datum:
15.08.2026.
Contemporary Materials 2026 - Savremeni Materijali
