Decay resistance and dimensional stability of wood impregnated with castor oil using a pressure treatment

Abstract This study was conducted to investigate the uptake of castor oil (CAO) in some wood specimens and the effect of CAO on the leaching ability, dimensional stability and fungal-decay resistance of the wood specimens. CAO was infused into the specimens using a pressure treatment. Uptakes of CAO penetrated in yellow poplar (YEP), Japanese cedar (JAC) and Douglas fir (DOF) blocks were higher than 100 %. The leaching ability of the CAO-based suspensions against saline water was the lowest in YEP, followed by Japanese larch (LAR), JAC and DOF. The retention values were 90 % or higher in most of the specimens. Radial and tangential swellings of CAO-treated strips submerged in saline water for 2 weeks were restrained compared to control specimens. No significant differences were found between bending strength and Janka hardness of CAO-treated and control strips. CAO treatment provided acceptable decay resistance to most wood specimens against Fomitopsis palustris and Trametes versicolor . Retention of CAO in the leached strips were identified through X-ray microscopic observation. Based on the results, CAO was determined to be an effective agent for improving the dimensional stability of wood. These results demonstrate the great potential of CAO as an environmentally friendly wood preservative and dimensional stabilizer, allowing CAO-permeated wood as raw materials for both indoor and outdoor use.