Time domain-NMR studies of average pore size of wood cell walls during drying and moisture adsorption

The change in the pore size of cell walls affects many physical properties of wood. In this paper, the dynamic changes in the pore size of wood cell walls during drying and moisture adsorption were studied at four relative humidities. The results showed that the average pore size of cell walls of Qingpi poplar (Populus- platyphylla var. glauca) was larger than that of pine wood (Pinus sylvestris var. mongolica Litv.) under the same experimental conditions, and the changes in pore size of Qingpi poplar cell walls were more sensitive to ambient humidity no matter whether during drying or moisture adsorption. Moreover, the average pore size of cell walls at saturated-water state is about 2.5 times of the average pore size of cell walls when woods reached the moisture absorption equilibrium from the oven-dry state. This article is useful for the wood manufacture industry and for wood modification. It is not only important for wood processing and utilization but also for the research on other porous materials.