Pore Characterization in Cross Section of Yellow Poplar (Liriodendron tulipifera) Wood

Abstract

This study was conducted to analyze the pore structure of Yellow poplar. Cross-sectional surfaces of heartwood and sapwood of Yellow poplar (Liriodendron tulipifera) were observed by SEM, and the true density of the heartwood, intermediate wood and sapwood were measured by gas pycnometery, while gas permeability and pore size of heartwood, intermediate wood and sapwood were measured by capillary flow porometery. The pores were classified as through pore, blind pore and closed pore. It was determined that the permeability was increased due to the content and size of through pore being increased although the total porosity of specimen showed slight difference from pith to bark. The content of through pore porosity was 33.754 % of heartwood and 47.810 % of sapwood, showed an increasing trend from pith to bark, however, those for the blind pore porosity and closed pore porosity were 27.890 % and 19.492 % for heartwood and 19.447 % and 4.660 % for sapwood, showed a decreasing trend from pith to bark. The max pore size of specimens was increased by about 5 times from $5.927{\mu}m$ to $31.334{\mu}m$, and mean flow pore size was increased by about 315 times from $0.397{\mu}m$ to $12.437{\mu}m$ from pith to bark.

Fig. 1. Preparation of Yellow poplar specimens.

Fig. 2. Schematic diagram of Helium gas intrusion during gas pycnometer measuring.

Fig. 3. The principle of separation of the pore types of wood specimens.

Fig. 4. The schematic diagram of gas permeability.

Fig. 5. The principal of capillary flow porometry using a capillary flow porometer.

Fig. 6. SEM images on the cross sectional surface of Yellow poplar.

Fig. 7. The results of Darcy permeability (H: heartwood, M: intermediate wood, S: sapwood).

Fig. 8. Bulk and true density of Yellow poplar (H: heartwood, M: intermediate wood, S: sapwood).

Fig. 9. Distribution of wood substance, through pore porosity, blind pore porosity and closed pore porosity of Yellow poplar (a : Heartwood, b : Intermediate wood, c: Sapwood).

Fig. 10. Max pore size and mean flow pore size of Yellow poplar measured by capillary flow porometer (H: heartwood, M: intermediate wood, S: sapwood).

Fig. 11. Correlation between gas permeability and total porosity, through pore size, max pore size and mean flow pore size in Yellow poplar.

Table 1. The results of pore analysis of Yellow poplar (H: heartwood, M: intermediate wood, S: sapwood)