| Summary: | Citric acid and starch have attracted considerable interest as potential modifiers for urea-formaldehyde (UF) adhesives, owing to their capability to improve performance and promote environmental sustainability. This study examined the impact of varying UF content added to a citric acid-tapioca starch adhesive system on the performance of rubberwood (Hevea brasiliensis) particleboard. The total resin content was set at 10%, with the adhesive composed of a mixture of citric acid (CA) and tapioca starch in a 75/25 ratio. UF was added to the adhesive in three different formulations: 2%, 5%, and 10% of the total resin content. The resulting particleboards were then tested for thickness swelling (TS), water absorption (WA), internal bond strength (IB), modulus of elasticity (MOE), and modulus of rupture (MOR). The findings indicated that increasing UF content improves the mechanical properties, such as the modulus of rupture (MOR) and modulus of elasticity (MOE). However, higher UF content also negatively impacts the physical properties, resulting in greater thickness swelling (TS) and water absorption (WA), which may compromise the overall dimensional stability and internal bond (IB) strength. The study concludes that UF content of around 5% offers an optimum property, achieving strong mechanical performance (IB = 0.207 N/mm2, MOR = 8.35 MPa, and MOE = 1645.15 MPa) while managing physical properties within acceptable ranges (TS-24H = 20.15%, WA-24H = 93.43%, Density = 565.36 kg/m ). © 2025 Forestry Department of Peninsular Malaysia. All rights reserved.
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