THE DRYING PERFORMANCE AND POST-DRYING QUALITIES OF Eucalyptus saligna EXPOSED TO INTERMITTENT AND CONTINUOUS DRYING

Abstract

THE DRYING PERFORMANCE AND POST-DRYING QUALITIES OF Eucalyptus saligna EXPOSED TO INTERMITTENT AND CONTINUOUS DRYING. Eucalyptus saligna tends to develop defects during its drying process, thus limiting its use as construction or furniture material. Intermittent drying, which applies non-heating phases between heating phases, has the potential to overcome this issue. This study evaluated the effects of 3 intermittent and one continuous schedule on the species' drying performance and post-drying qualities. The results showed that the boards from all intermittent schedules exhibit significantly slower drying rates (from-9.4x10-3 %/hour to-1.57 x10-2 %/hour) than those from the continuous schedule (from-5.12 x10-2 /hour to-1.03 x10-2 %/hour). All intermittent schedules tended to decrease the collapse depth in E. saligna boards (the average value range of the three schedules was 1.162-2.032 mm) than the continuous schedule did (the average value was 5.12 mm). Nevertheless, applying higher temperature than that used in the continuous schedule, during the heating phase of the intermittent schedule, potentially increased the moisture gradient, residual drying stress, end check length, internal check percentage, and spring depth.

Variation of perpendicular compressive strength properties related to anatomical structure and density in Eucalyptus nitens green specimens

“…In general terms, collapse is an abnormal shrinkage that occurs above the fiber saturation point, and it is caused by capillary forces that arise as the free water is eliminated (Chafe et al 1992). When these forces exceed the compressive strength of the cell walls, the flattening of cell can be produced (Yuniarti et al 2015;Bond and Espinoza 2016). Pérez et al (2018) measured the compression stresses as high as 9 MPa during the drying of E. nitens samples, which could explain the tendency to collapse and the development of internal checking.…”