Micro-distribution, water absorption, and dimensional stability of wood treated with epoxidized plant oils

Abstract

Samples of Scotch pine sapwood were treated with epoxidized linseed and soybean oils via an empty cell process to improve the hydrophobic properties of wood. Boric acid was included to introduce fungicidal properties into the oils. Two retention levels (80 to 140 kg/m3 and 170 to 270 kg/m3) were targeted for oil treatments. Both an empty cell method and emulsion techniques were used to combine epoxidized oils and boric acid in a one-step treatment. Iodine number changes, Fourier transform infrared spectroscopy (FTIR), water absorption (WA), anti-swelling efficiency (ASE), and scanning electronic microscopy (SEM) analyses were used to characterize the wood after treatment. High iodine number changes that indicated a reduction the amount of unsaturated double bonds were determined. The FTIR analysis of epoxidized oils revealed a peak at 820 cm-1, which indicated that epoxide moieties (C-O-C) were present. All of the oil treatments resulted in statistically significant lower water absorptions than the control sample. The lowest water absorption values were obtained from wood treated with epoxidized oils. The highest ASE result (70%) was observed on samples treated with epoxidized soybean oil at low retention (108 kg/m3). It was also determined that most of the latewood tracheids were filled with oils when compared to the earlywood tracheids.