Drying characteristics, hygroscopicity, and dimensional stability of natural tung oil dried bamboo

Drying with hot oil is considered to simplify the process and improve the production efficiency of bamboo treatment. Herein, tung oil was used to dry and modify fresh bamboo. After bamboo samples were dried in tung oil at 110 °C, the changes in the mass of bamboo, moisture absorption, dimensional stability, surface morphology, and chemical structures were analyzed. The results illustrated that tung oil could dry bamboo rapidly and oil-dried bamboo had an improved hydrophobicity and dimensional stability. NMR results showed that the peak areas of free water and bound water both decreased with increasing drying time, while the peak positions continuously shifted toward the shorter transverse relaxation time. The moisture repellent effect (MRE) and anti-swelling efficiency (ASE) of tung oil-dried bamboo were 53.90% and 65.20%, respectively. Moreover, the water absorption was reduced by 49.89%, and the ASE of the tung oil-dried bamboo under water-saturated conditions could reach approximately 37.21%. The oil-dried samples had larger contact angles in the short term. Moreover, tung oil was able to penetrate the bamboo and solidify at the internal surface, occluding the channels that enabled water flow. Additionally, tung oil-drying decreased the hydrophilic groups and partially modified the chemical structure of bamboo.