Urea formaldehyde impregnated oil palm trunk as the core layer for three-layered board

•We investigate effect of UF impregnation on OPT physical and mechanical properties.•Impregnated OPT offers better dimensional stability and strength, except with sMOE.•Impregnation pressure and time had little effect on its properties.•Higher resin solid content gave better physical and mechanical properties.•The optimum impregnation treatment is with 30% UF solid content.

Huge amount of oil palm trunks were made available during replanting activities to replace the unproductive oil palm trees. In this study, 30-years old oil palm trunks were used. The oil palm trunk (OPT) were treated respectively with different solid content (10%, 20% and 30%) of aqueous urea formaldehyde (UF) under three level of impregnation pressure 8 MPa, 10 MPa and 12 MPa for 15 min, 30 min and 60 min. Three-layered board was produced by laminating impregnated OPT with 0.5 mm thick veneer at 180 g/m2 glue spread rate and hot pressed using 6 MPa pressing pressure at temperature of 110 °C for 4 min. It was observed that increase of impregnation pressure and time did not improve the physical and mechanical properties of the three-layered board. The results from soaking test showed that the three-layered board produced from OPT impregnated with higher resin solid content and shorter impregnation time eventually reduced the degree of water absorption and resulted in dimensional changes of its thickness and width. Furthermore, the impregnation treatments on the core layer increased the modulus of rupture (MOR) and shear strength of the board but a reduction in modulus of elasticity (MOE). The optimum UF impregnation treatment which produced the highest mechanical and physical properties was the treatment with 30% UF solid content, 10 MPa impregnation pressure and 15 min impregnation time.