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SEM images of some kinds of wood used in this study. a-e, softwoods. a, P. densiflora. b, P. radiata. c, P. menziesii. d, A. sachalinensis. e, C. deodara. f-i, hardwoods. f, A. julibrissin. g, C. crenata. h, Z. ailanthoides. i, P. alba
Source publication
Dynamic mechanical analysis (DMA) measurements of water-saturated earlywood (EW) and latewood (LW) of various wood species in the temperature range from 0 to 100 °C were focused to clarify the differences in thermal softening properties within an annual ring. The following results were obtained. The peak of tan δ caused by micro-Brownian motion of...
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... samples were dried at 105 °C for 24 h, and then the cross-section was observed using SEM (TM3030 Plus Miniscope, Hitachi High-Technologies, Tokyo, Japan) at an accelerating voltage of 15 kV. Figure 3 shows SEM images of the wood used in this study. It can be seen that the specimens used in this study are normal wood, neither reaction wood nor starved wood. ...
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... Miniscope, Hitachi High-Technologies, Tokyo, Japan) at an accelerating voltage of 15 kV. Figure 3 shows SEM images of the wood used in this study. It can be seen that the specimens used in this study are normal wood, neither reaction wood nor starved wood. Cedrus deodara was found to spew extractable components like carbohydrates, as shown in Fig. 3e. Narrow vessel were abundant in LW of g (Castanea crenata) and h (Zanthoxylum ailanthoides) is a diffuse-porous wood, but the vessel in LW were slightly smaller and less numerous than those in EW. As mentioned above, it has been reported that guaiacyl lignin is enriched in the S2 layer of vessels, syringyl lignin in the S2 layer of ...
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... direction (EW) ▲ ▲ ▲ Radial direction b c a d e f g h i Fig. 4 Temperature dependence of E′ in tangential and radial direction of some kind of wood swollen by water at 0.5 Hz. Green filled circles and triangle, LW; orange filled circles and triangle, EW; yellow filled circles and triangle, R specimen. a-e, Softwoods. f-i, Hardwoods. See Fig. 3 for more details peaks of tanδ are found from 85 to 95 °C, whereas in hardwood, those are found from 75 to 85 °C at 0.5 Hz. For softwoods, the peak temperature of tanδ of EW at 0.5 Hz appeared at higher temperatures than those of LW as in the previous report [8]. In addition, the peak temperature of tanδ of R specimens was similar to ...
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... (LW) ▲ ▲ ▲ Tangential direction (EW) ▲ ▲ ▲ Radial direction Fig. 5 Temperature dependence of E′ in tangential and radial direction of some kind of wood swollen by water at 10 Hz. Green filled circles and triangle, LW; orange filled circles and triangle, EW; yellow filled circles and triangle, R specimen. a-e, Softwoods. f-i, Hardwoods. See Fig. 3 for more details that the benzene ring of the guaiacyl unit on the surface of the lignin unit is oxidized to form a carboxyl group in the initial stage of delignification (treatment time 10 min), although the mass loss is slight [20,21]. Even in the initial stage of delignification, the thermo-softening temperature decreases by about 5 ...
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... (LW) ▲ ▲ ▲ Tangential direction (EW) ▲ ▲ ▲ Radial direction Fig. 6 Temperature dependence of tanδ in tangential and radial direction of some kind of wood swollen by water at 0.5 Hz. Green filled circles and triangle, LW; orange filled circles and triangle, EW; yellow filled circles and triangle, R specimen. a-e, Softwoods. f-i, Hardwoods. See Fig. 3 for more details found that the difference in the peak value of tanδ and the peak temperature of tanδ between EW and LW was smaller for hardwoods than for softwoods, regardless of species. On the other hand, for softwoods, the difference in the peak temperature of tanδ between EW and LW varied greatly among species. The species with ...
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... (LW) ▲ ▲ ▲ Tangential direction (EW) ▲ ▲ ▲ Radial direction Fig. 7 Temperature dependence of tanδ in tangential and radial direction of some kind of wood swollen by water at 10 Hz. Green filled circles and triangle, LW; orange filled circles and triangle, EW; yellow filled circles and triangle, R specimen. a-e, Softwoods. f-i, Hardwoods. See Fig. 3 for more details into consideration that different wood species have different the peak temperature of tanδ within an annual ring and ...
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... a maximum difference of 5 °C. The difference in the peak temperature of tanδ between the R and T directions Softwoods ▲ ▲ ▲ Tangential direction (LW) ▲ ▲ ▲ Tangential direction (EW) ▲ ▲ ▲ Radial direction triangle, the difference between EW and R specimens; rhombus, the difference between LW and R specimens. a-e, Softwoods. f-i, Hardwoods. See Fig. 3 for more details was small for both softwoods and hardwoods. However, the peak value of tanδ was larger in the T direction, especially for hardwoods. Nuclear magnetic resonance ATR-IR Attenuated total reflection-infrared spectroscopy Author contributions HH designed the study, collected and analyzed data and wrote the initial draft of ...
Citations
... Numerous scholars have extensively explored the differences in the tensile mechanical properties between EW and LW at a given temperature and moisture content (MC) level [6][7][8][9][10][11][12]. Roszyk [7] reported on the tensile mechanical behavior of the EW and LW of pine wood (Pinus sylvestris) in the longitudinal (L) direction in the wet and air-dry states, and found that tensile strength, modulus of elasticity, and stress at the proportionality limit of EW and LW decreased generally as the MC increased. ...
... It is well known that wood strength decreases with temperature. The wood cell wall polymers are provided with heat energy for segmental motion, resulting in the decrement of wood stiffness [11,12]. Differences in density, microfibril angle (MFA), chemical compositions, and cell structure might be the reasons for the differences in the tensile mechanical properties of EW and LW [13][14][15][16]. ...
... Likewise, the tensile mechanical behavior of wood differs vastly in the L direction and in the transverse directions [17][18][19]. In general, previous comparative studies on the tensile mechanical behavior of EW and LW mainly focused in the L direction [7][8][9][10]; little research had been conducted on the tensile mechanical properties of EW and LW in the tangential (T) direction [12]. Horiyama et al. [12] investigated the tensile dynamic mechanical properties of water-saturated EW and LW within an annual ring in the T direction in the temperature range from 20 • C to 100 • C, and found that the dynamic modulus of LW was larger than that of EW for all wood species, regardless of softwood or hardwood. ...
The tensile mechanical behavior of water-saturated earlywood (EW) and latewood (LW) within the same growth ring of Masson pine (Pinus massoniana) was investigated in the hydrothermal environment and discussed with respect to the density and microfibril angle (MFA) of the wood specimens. The tensile modulus, tensile strength, and strain at failure of EW and LW in the longitudinal (L) and tangential (T) directions were determined at different temperature levels ranging from 30 °C to 80 °C. Major differences in the tensile mechanical properties were found between EW and LW in the L and T directions. Compared to LW, EW showed a smaller density and a larger MFA, resulting in a lower tensile modulus, lower tensile strength, and higher strain at failure. Compared to the L specimens, the T specimens showed lower tensile modulus, lower tensile strength, and higher strain at failure. As the hygrothermal temperature increased, the MFAs, tensile modulus, and tensile strength of EW and LW specimens decreased, except for the MFAs of LW, while the strain at failure of the specimens showed the opposite trend. Variations in the tensile mechanical behavior between EW and LW were mainly influenced by the density and MFA of the specimens, and are closely associated with the hydrothermal softening properties of wood. These findings contribute to a further understanding of the structural–mechanical relationships of Masson pine wood at the cell wall level, and provide a scientific basis for the better utilization of plantation softwood in the hydrothermal environment.
... We also focused on the dynamic mechanical analysis (DMA), a method that can measure the viscoelastic properties of wood. Viscoelastic properties of wood have been used to understand the structure of wood at the molecular level, because they strongly reflect the effect of the structural state of wood components [23][24][25][26][27]. For example, it has been reported those the thermal softening behavior of water-saturated wood changes when the structure of lignin in the cell wall changes [25]. ...
... Our previous studies have shown that the thermal softening properties of EW and LW of Douglas fir are different, with a peak of tanδ at about 95 °C for EW and 90 °C for LW [23]. Peak temperatures of tanδ have also been shown to be lower for LW than for EW in other softwoods [24]. ...
Dynamic mechanical analysis (DMA) measurements of water-saturated radiata pine wood in the temperature range from 0 ℃ to 100 ℃ were focused to clarify the transition in viscoelastic properties within successive annual rings. Four radially consecutive specimens were taken per annual ring and DMA measurements in the tangential direction were performed using these specimens. The following results were obtained. The peak of tan δ caused by micro-Brownian motion of lignin was observed in all samples. The temperature of peak tan δ tended to decrease from earlywood to latewood within an annual ring. The temperature of peak tan δ increased across annual ring boundary. The same trend was repeated within the next annual ring. It was found that the viscoelastic properties transitioned within successive annual rings.
