WOOD RESEARCH Volume 70, Number 2, 2025
LIN YANG, PUYAN ZHAO, and QIN YIN

STUDY ON THE HYDROTHERMAL TREATMENT OF KILN-DRIED TIMBER OF RED ALDER

This study used red alder (Alnus rubra f. pinnatisecta) and applied humidity control during storage to shorten the health cycle and enhance preservation effects. Orthogonal testing was conducted to assess the impact of humidity control on drying quality and identify optimal conditions. The results showed that: 1) Post-humidity control, most materials exhibited high surface and low core moisture distribution. Surface moisture difference before and after treatment was largest and negatively correlated with moisture increase. Higher temperatures reduced differences at the same treatment duration. 2) Reasonable humidity control significantly improved drying quality: surface moisture remained stable, elastic and mechanical adsorption creep strains decreased, and residual stress was reduced by up to 59.5% after 7 days of humidity and curing compared to room temperature curing. 3) Moisture treatment initially reduced residual stress significantly then rebounded slightly, with stress elimination efficiency generally higher than room temperature. This indicates that humidity control shortens wood storage and curing cycles. 4) Orthogonal test results identified optimal humidity control conditions as 70°C, 85% relative humidity, and 48 h treatment

WOOD RESEARCH Volume 70, Number 2, 2025
LIN YANG, HONGWEI FAN, and JINGTING ZHENG

EFFECT OF SUPERCRITICAL CO2 DEHYDRATION TREATMENT ON THE JUGLANS MANDSHURICA

Conventional kiln drying (CKD) has a long drying period and is easy to cause drying defects. Supercritical CO2 dehydration (SCD) can quickly dehydrate water-saturated wood to above the fiber saturation point without damaging the microstructure and avoiding drying defects. In this study, Juglans mandshurica was treated by SCD to 40% moisture content, then was oven-dried. CKD specimens were used as a control to investigate the effect of SCD treatment on the wood properties of Juglans mandshurica. In the moisture absorption test, the equilibrium moisture content of the SCD and CKD samples was found to be 8.95% and 8.66%, respectively.The final tangential and radial swelling of the SCD samples were 2.5% and 2.03%, respectively, which were 0.1% and 0.24% larger than those of the CKD samples. In the water uptake test, the equilibrium moisture content of SCD and CKD samples was found to be 104.79% and 117.71%, respectively. The final tangential and radial swellings of SCD specimens were 9.38% and 4.6%, which were 2.35% and 1.16% larger than those of CKD specimens. Also, it was confirmed that the extraction content of SCD specimen was reduced, the chemical composition was unchanged, and the open diameter of the pits was about 1.35 μm at 20 MPa/60°C

WOOD RESEARCH Volume 65, Number 6, 2020
LIN YANG, Tianqi Han, and Yudong Fu

Effect of heat treatment and wax impregnation on dimensional stability of Pterocarpus macrocarpus wood

In order to improve dimensional stability and control deformation, heat treatment (HT) and wax impregnation (WI) were conducted to large size boards (LB) of Pterocarpus macrocarpus and the tangential swelling were compared in various relative humidity (RH) conditions. The results show that the tangential swelling and shrinking of control group and treated group performed differently corresponded to various relative humidity (RH). Comparing with control group, the swelling ratio of HT combined WI group was much less, and followed by 180°C-3h HT group. The maximum swelling ratio decreased by 31% and 29% in humidity chamber and indoor conditions respectively. The swelling ratio was affected by size of samples, LB showed smaller welling ratio than small sample. Wax filled in cell cavities and presented uneven distributions after impregnation. The rate of wood hygroscopicity was reduced after HT combined WI treatment which was an effective method on improvement of wood dimensional stability.