IMPROVING THE DIMENSIONAL STABILITY OF MULTILAYERED STRAND BOARD THROUGH RESIN IMPREGNATION

Abstract

PARIDAH, M. T., ONG, L. L., ZAIDON, A., RAHIM, S. & ANWAR, U. M. K. 2006. Improving the dimensional
stability of multi-layered strand board through resin impregnation. Three- and five-layered strand boards
were fabricated using Acacia mangium strands bonded with specially formulated low molecular weight phenol
formaldehyde (LPF) resin. The mean density of the boards was 650 kg m^–3. The aim of this study was to
evaluate the effectiveness of pre-treatment of wood strands with LPF resin to improve the dimensional
stability of strand board. The LPF resin was impregnated into the green wood strands prior to spraying with
conventional phenol formaldehyde (PF). The furnish was dried by blowing hot air onto the strands to
moisture contents between 10 and 11%. The amount of PF resin was fixed at 5% and that of LPF, at 2, 5
and 7% resin solids based on oven-dry weight of wood strands (w/w). The mechanical properties and
dimensional stability of the panels were affected by both the amount of LPF resin incorporated as well as
board structure (three- and five-layered). The LPF pre-treatment successfully reduced the thickness swelling
of the strand board by > 20%, but the internal bond strength obtained was found to be of inferior grade
and the curing time needed to be extended by 25%. The study showed that the dimensional stability and
mechanical properties of the strand board could be improved through initial impregnation of wood strands
with 7% LPF resin and consolidated at 175 °C for at least 10.5 min press time.