“…Very low permeability in a perishable wood such as Paulownia is a real drawback, as it makes it difficult to be impregnated with preservatives. However, some methods were developed to improve the permeability in this species, among which supercritical carbon dioxide is the latest (Xu et al 2019). HT at all three temperatures resulted in significant increase of sapwood and heartwood K g values (Figure 6).…”
Section: Resultsmentioning
confidence: 99%
“…However, some methods were developed to improve the permeability in this species, among which supercritical carbon dioxide is the latest (Xu et al. 2019). Figure 8 Liquid permeability ( K l ) (hours) of 50-mm lowering time in the sapwood and heartwood specimens of the control, as well as heat-treated specimens at 180°C, 190°C, and 200°C.…”
Fibre direction cylindrical specimens from the sapwood and heartwood areas of Paulownia wood were heat treated at 180, 190, and 200°C split in eight groups of ten specimens each. Air and water permeability were measured, thereafter. Results demonstrated that heat treatment had a positive effect on air permeability both in sapwood and heartwood specimens. That increase might be attributed to the development of cell wall micro-checks caused by thermal degradation and fracture of the vessel tyloses. Liquid permeability was significantly decreased as a result of heat treatment.
“…Very low permeability in a perishable wood such as Paulownia is a real drawback, as it makes it difficult to be impregnated with preservatives. However, some methods were developed to improve the permeability in this species, among which supercritical carbon dioxide is the latest (Xu et al 2019). HT at all three temperatures resulted in significant increase of sapwood and heartwood K g values (Figure 6).…”
Section: Resultsmentioning
confidence: 99%
“…However, some methods were developed to improve the permeability in this species, among which supercritical carbon dioxide is the latest (Xu et al. 2019). Figure 8 Liquid permeability ( K l ) (hours) of 50-mm lowering time in the sapwood and heartwood specimens of the control, as well as heat-treated specimens at 180°C, 190°C, and 200°C.…”
Fibre direction cylindrical specimens from the sapwood and heartwood areas of Paulownia wood were heat treated at 180, 190, and 200°C split in eight groups of ten specimens each. Air and water permeability were measured, thereafter. Results demonstrated that heat treatment had a positive effect on air permeability both in sapwood and heartwood specimens. That increase might be attributed to the development of cell wall micro-checks caused by thermal degradation and fracture of the vessel tyloses. Liquid permeability was significantly decreased as a result of heat treatment.
“…Permeability is an important physical property of wood that affects its drying properties, impregnation, and sound absorption [1][2][3][4], determining many of its applications as a porous material. Modifications for improving the gas permeability of wood have been studied since the 1930s, and remain a popular research topic [5].…”
Section: Introductionmentioning
confidence: 99%
“…Modifications for improving the gas permeability of wood have been studied since the 1930s, and remain a popular research topic [5]. For example, Xu et al [2] reported that supercritical carbon dioxide (SC-CO 2 )-treated Paulownia fortunei could remove tyloses in vessels to improve permeability. Tanaka et al [3] reported that Douglas-fir pit aspirations, margo, and torus were destroyed after ultrasonic treatment, improving permeability.…”
This study investigated changes in the sound absorption coefficients of three anatomical sections of cubed spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment. Microwave treatment at 1000 W and 2.4 GHz for 20 min increased the sound absorption coefficients (at 2000–5000 Hz) of spruce by 6.9% in the transverse section, 20.0% in the radial section, and 31.7% in the tangential section. The sound absorption coefficients of Douglas fir increased by 28.9% in the transverse section, 19.1% in the radial section, and 50.0% in the tangential section. Larch coefficients increased by 16.7% in the transverse section, 37.2% in the radial section, and 38.8% in the tangential section. The sound absorption coefficients of the softwoods differed according to species and anatomical plane after microwave treatment. It was concluded that changes in the measured sound absorption coefficient indicate alteration in the pore structure of wood, which can affect in turn wood permeability and impregnation. These data will be helpful for predicting the permeability and impregnation of wood after microwave treatment.
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