WOOD RESEARCH Volume 68, Number 3, 2023
Qiaofang Zhou, Dongdong Liang, Aokai Cheng, Xianju Wang, and Dengyun Tu

Effects of Pressing Temperature and Compression Ratio on Density Distribution and Hardness of Surface Densified Poplar Wood

Process parameters play an important role in wood surface densification. In this study, the poplar (Populus tomentosa Carr.) wood was heated on one side at 100℃, 150℃ and 180℃, and compressed in the radial direction with the speed of 10 mm/min. The initial thickness of the wood samples were 30 mm, 26 mm and 23 mm, and they were all compressed to 20 mm and resulting in three different compression ratios: 33.3%, 23.1% and 13.0%. When the surface densification completed, the density distribution and hardness of the densified and un-treated samples were measured and analyzed. Results show that the compressing temperature mainly decided the formation of the density distribution curve and the peak density increased with the increasing temperature; as the compression ratio increased, the peak density increased and the thickness of the densified zone broadened; the surface hardness was highly correlated with the density distribution which was affected by temperature and compression ratio, and as the peak density increased and the thickness of the densified broadened the hardness increased accordingly. Therefore, by optimizing the process parameters such as the compressing temperature and compression ratio could generate a targeted density distribution which has the desired hardness.

WOOD RESEARCH Volume 67, Number 6, 2022
Aokai Cheng, Dengyun Tu, Zhipeng Zhu, Qiaofang Zhou, Wei Wei, Chuanshuang Hu, and Xianghao Liu

Study on machining properties and surface coating properties of heat treated densified poplar wood

In this study, a modification combining densification and heat treatment of poplar wood (Populus tomentosa Carr.) was carried out, and the machining properties of the unmodified poplar wood (control) and the heat treated densified wood (HTD) were tested and evaluated. In addition, the water-based UV paint was covered on the control and HTD respectively, and the surface coating properties of them were evaluated. The results showed that: (1) The machining properties of poplar wood were improved after the heat treatmentdensification modification. The score of comprehensive machining properties of the HTD was 45 (excellent grade), while the score of the control was 36 (good grade). (2) The abrasion resistance, hydrophobicity and adhesion were improved after heat treatment-densification modification. Therefore, the modification combining densification and heat treatment played a significant role in enhancing the value of wood.

WOOD RESEARCH Volume 61, Number 2, 2016
Hong Yun, Kaifu Li, Dengyun Tu, and Chuanshuang Hu

Effect of heat treatment on bamboo fiber morphology crystallinity and mechanical properties

This study aimed to investigate the fiber morphology, crystalline structure and mechanical properties of heat-treated bamboo. Moso bamboo was treated by superheated steam at 120, 140, 160, and 180ºC. Fiber morphology and crystalline structure of heat-treated Moso bamboo were researched by transmission electron microscope and X-ray diffraction. The mechanical properties of heat-treated bamboo were tested in the paper. The result showed that the relative crystallinity and length-width ratio of heat-treated bamboo were increased with increased temperature. The elastic modulus of bamboo was increased as the temperature rose from 120 to 140ºC. and then decreased with higher temperature, which was associated with the increase of the crystallinity.

WOOD RESEARCH Volume 62, Number 2, 2017
Hong Yun, Kaifu Li, Chuangshuang Hu, and Dengyun Tu

Adsorption and fixation of soluble fire retardancy in Populus russkii and Cunninghamia lanceolata

Flame retardant treatment is a common method of wood preservation. However, the factory usually uses the same approach to all the wood, but lack of targeted so as to cause waste. This study used poplar and Chinese fir as the species investigated. These species were dipped with boron-nitrogen-phosphorus (B-P) fire retardant. The influences on material loading of processing method, concentration of fire retardant, and drying method were investigated. The contents of B and P were tested by inductively coupled plasma optical emission spectrometry (ICP-OES), after distilled water washing and ultrasonic washing. The results showed that the volume loading increased with the concentration of fire retardant. Freeze-drying can noticeably improve the volume loading, and the impact of the drying method was more notable on poplar than on Chinese fir. The fixation effect of the B and P in poplar was lower by ultrasonic washing than that was by distilled water washing. The fixation effect was opposite in the Chinese fir. Vacuum process was more suitable for the poplar (hardwood), and vacuum-pressure process was
more suitable for the Chinese fir (soft wood).

WOOD RESEARCH Volume 64, Number 1, 2019
Xiangyu Zhao, Dengyun Tu, Chuanfu Chen, and Qiangfang Zhou

Prediction of the mechanical properties of thermally-modified rubber wood on the basic of its surface characteristic

The goal of this research was to investigate the effect of thermal treatment on mechanical properties and surface characteristic of rubberwood (Hevea brasiliensis) and find the mathematical model to predict the mechanical properties used by its surface characteristic. Rubberwood specimens were treated by steaming at five different temperature levels of 170, 185, 200, 215, and 230°C for two different durations of 1.5 and 3 h. Based on the results, the values of bending strength, modulus of elasticity, compression strength and impact bending decreased, and the glossiness and chromatic aberration (∆E) increased with increasing temperature and enlarging duration further. This study revealed that chromaticity parameters b*, ∆E and the gloss of perpendicular to grain (GZT) could evaluate the mechanical properties of thermally-modified wood to achieve the mechanical properties detection without destruction.

WOOD RESEARCH Volume 66, Number 1, 2021
Zhipeng Zhu, Dengyun Tu, Ziwei Chen, Chuanfu Chen, and Qiangfang Zhou

Effect of hot pressing modification on surface properties of rubberwood (Hevea brasiliensis)

This research aims to investigate the effect of thermal modification by hot pressing on surface characteristics of rubberwood. For this purpose, rubberwood specimens were thermally modified by hot pressing in an open system at three different temperatures (170, 185, and 200°C) for two different durations (1.5 or 3 h). Based on the results, the values of chromatic aberration (ΔE), contact angle and glossiness increased, and roughness decreased with increasing temperature and enlarging duration further. Although the contact angle had increased, it was still less than 90°. This aesthetic surface of rubberwood could be retained by using transparent organic coatings. The thermally modified rubberwood with excellent performance could be used as a material for solid wood flooring, wallboard, and furniture applications.