Effect of different drying methods on liquid penetration of Chinese fir plantation wood

Abstract

On the other hand, plantation-grown Chinese fir is really a refractory species. Usually, it requires very high pressure to impregnate the wood with chemicals or resins, while the high pressure could result in damage and deformation of the wood. It has been reported that liquid permeability varies depending on drying methods and that pre-or post-treatments could improve permeability (Matsumura et al., 1995a(Matsumura et al., , 1995b(Matsumura et al., , 1996Zhao et al., 2003), but few reports were found with respect to the effect of different drying methods on liquid penetration of wood. Therefore, to understand the mechanism of drying methods on liquid penetration of plantation-grown Chinese fir is a key project to make high quality, solid wood products from this species through various chemical impregnation treatments. This paper comprises a comparative study on the effect of radio frequency/vacuum drying (RFVD), conventional kiln drying (KD) and high temperature drying (HTD) on the liquid penetration of Chinese fir plantation wood. Materials and methods MaterialsFifteen Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation-grown trees were cut in Jiangxi Province. Under the same planting condition, five rapidly grown trees were selected (diameter of breast height (DBH)>25 cm), five trees grown at a medium speed (23 cm<DBH<25 cm) and five slow growing trees (DBH<23 cm). Methods Specimen preparationLogs less than 1.3 m in length were cut from each tree, part of the logs from a southern exposure were used for drying experiments; 2-3 pieces of heartwood and sapwood boards of 1.3 m in length and 30 mm thick were sawn from pith to bark. These boards were cut into 80-mm wide and 25-mm thick lumber. Finally, three specimens, 30 cm long, were cut in the longitudinal direction of tree's growth and randomly selected Abstract Chinese fir plantation sapwood and heartwood boards were treated by three drying methods: radio frequenc yvacuum drying (RFVD), conventional kiln drying (KD) and high temperature drying (HTD). The maximum amount of dyeing solution uptake by the capillary rising method was used to evaluate the liquid penetration of the treated wood. The pit aspiration ratio was determined by a semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results show that liquid penetration of Chinese fir sapwood after RFVD is significantly higher than that after KD and HTD. Liquid penetration of Chinese fir heartwood after RFVD is higher than that after HTD. Liquid penetration of Chinese fir sapwood is significantly higher than that of heartwood after three drying treatments. Low pit aspiration ratio and cracks of some bordered pits are the main reasons for the increase in liquid penetration after RFVD treatment.

Effects of drying temperature for Cryptomeria japonica on the permeability of wood preservative I. The permeability of dried logs

“…According to Lü et al (2007), one reason for pit aspiration is that a high temperature decreases the rigidity of the pit membrane; in this study, the rigidity decreased with increasing drying temperature. The other cause of aspiration is the rapid evaporation of water at a high temperature, and the surface tension causes the pit torus to move to the aspirated position.…”