• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.726-735
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• 2016

This study was carried out to evaluate the high-temperature drying characteristics of douglas-fir, hemlock, and radiata pine square timber with dimensions of thickness 15 cm and 18 cm. As a result, radiata pine showed the lowest final moisture content followed by douglas-fir and hemlock without reference to the timber size. Moreover, when the longitudinal kerfing is processed, the final moisture content was lower than control. The kerfing treatment was effective to decreasing the twist of radiata pine and hemlock. When douglas-fir is processed to the shape like the edge-grained timber that does not include the pith, the decrease of drying defect was possible.

• Korean Journal of Agricultural Science
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• v.21 no.2
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• pp.103-110
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• 1994

Since the supply of the Southeast Asian tropical timber decreases and its price steeply increases in the international lumber market, door and window frame manufacturers in this country are eagerly searching for their substitutes. This is the first step to replace Southeast Asian tropical timber by low grade North American softwoods, whose reliable and steady supply is expected, but their appearances are not as good as the tropical timber. In this study, knot distribution on the softwood boards and their warp were examined The yield and production cost were also calculated. The average numbers of knots on a door frame were 7.2 for Douglas-fir and 3.4 for Western hemlock. Only 11% of the knots of Douglas-fir door frames are larger than 5cm in diameter, while are 35% of the knots of Western hemlock. The deformations of door frames, after 2 months air-drying, were measured with a warp table. The deformations of Western hemlock door frames were mostly less than 6mm, while those of Douglas-fir distributed in the range of 0.5 and 9.5mm. The yield of Western hemlock is higher than that of Douglas-fir. It can be concluded that the door frames made of the softwoods are compatible with those made of the tropical timber in most aspects except appearance.

• Journal of the Korean Wood Science and Technology
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• v.16 no.4
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• pp.40-47
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• 1988

Our plywood manufacturing industries which entertained prosperous stage in late 1970's have come to be in face of the problems of conceedingly obtaining good quality logs and yield up-grading, which is considered by future-replaceable forest resources. In view of this point, manufacturing characteristic on softwood plywood using Japanese larch, pitch pine as domestic plantation species, and western hemlock as foreign species was studied. In this study, veneer- and plywood manufacturing yields were discussed in relation to log properties and veneer defects (knots). The summarized conclusions were as follows: 1. The majority of sample logs belonged to second grade on the standard. And, eccentricity of larch was the highest 11%, about 2 times those of pitch pine, hemlock. 2. Knot frequency of occurrence of larch reached 19% within log height 8m, and pitch pine 13% within 4m. Correspondingly, the log height of larch available for plywood manufacture was higher by about 2 times that of pitch pine. 3. In the knot types, most of knots of larch appeared dead, whereas those of pitch pine and hemlock appeared live. In size of knots, larch and hemlock showed relatively small 1-2cm dia. by 70% or more and pitch pine did the larger 24cm by 65%. Generally the more knot emerged in the inner side of veneer than the outer. 4. Plywood manufacturing yields by peeling with spindle revolution lathe were 37% in larch > 32% in hemlock> 26% in pitch pine. S. Jointed core veneer yields by peeling with outer perimeter back-up lathe were 55% in hemlock> 53% in larch> and 48% in pitch pine.

• Journal of the Korean Wood Science and Technology
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• v.26 no.4
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• pp.34-42
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• 1998

Three hardwood (ash, alder and black locust) and three softwood (Japanese red pine, radiata pine and Western hemlock) specimens were dried in microwave(MlW) oven and their drying rates were obtained. Their specific permeabilities were also measured by using a modified liquid permeability measuring device. The correlation between the M/W drying rates and permeabilities of six species were statistically analyzed. It was revealed that within a species there is a logarithmic relationship between the M/W drying rates and average moisture contents and that among species there is a linear relationship between the M/W maximum drying rates and the average specific permeabilities. A exception was Western hemlock, which was of low permeability and of high drying rate. A Me-time equation, which showed a good agreement with the actual data, was derived. Thus using this equation the moisture contents of wood and the drying end points of M/W drying could be predicted. Infrared images of the thermal distribution in wood were illustrated.

• Journal of the Korean Wood Science and Technology
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• v.12 no.3
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• pp.15-24
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• 1984

The $3{\times}3{\times}30\;cm^3$ sized specimens of Douglas-fir(Pseudotsuga menziesii) and western hemlock(Tsuga heterophylla) in this study were soaked in four fire-retardant solutions of ammonium sulfate, monoammonium phosphate, diammonium phosphate, and aluminium chloride for 1, 24, 72, 168, and 336 hours. Subsequently they were air-dried and burned at high temperature of ca. $1,800^{\circ}C$ and for short time of 5 minutes. This study estimated the relationship between the adsorbed chemicals and the residual weight ratio or residual bending strength of these partly burned lumbers. The results were as follows; 1) In average amount of chemical adsorption, diammonium phosphate showed the largest and aluminium chloride the smallest regardless of species but monoammonium phosphate was larger in Douglas-fir than that of western hemlock. 2) The amount of chemical adsorption was larger in western hemlock than Douglas-fir on the whole. 3) The amount of chemical adsorption was increased with the increase of soaking time but the rate of increase began to decrease at 200hrs. 4) Residual weight ratios showed no difference between species but showed differences among the chemicals treated i.e. monoammonium phosphate, diammonium phosphate, ammonium sulfate and aluminium chloride in turn from the largest to the smallest. 5) MOR values showed linear increase with the increase of residual weight ratios but showed no difference in species and chemicals respectively. 6) In the relationship between amount of chemical adsorption and MOR, only diammonium phosphate showed the curve of secondary degree with significance in Douglas-fir. 7) The MOE value of burned Douglas-fir lumber increased and showed significance of 99% as the adsorbed chemical amount increased, but among the chemicals only monoammonium phosphate showed significance. The MOE value of burned western hemlock lumber didn't show significance. 8) In only Douglas-fir, the correlation between adsorbed chemical amount and work to proportional limit showed significance in only monoammonium phosphate. And in both Douglas-fir and western hemlock, the correlation between adsorbed chemicals and work to maximum load showed significance in monoammonium phosphate.

• Journal of Bio-Environment Control
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• v.15 no.1
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• pp.100-106
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• 2006

A hypertonic solution of sorbitol was used to precondition Douglas-fir and Western hemlock plug seedlings to improve desiccation resistance. Seedlings were preconditioned by soaking their root balls in water, -0.75 or -1.50 MPa sorbitol solution for 22 hr, and then exposed to desiccation conditions for 8 days. During the desiccation period, a transpirational water loss was significantly reduced by the sorbitol preconditioning, with its effect positively depending on concentration. This preconditioning-induced reduction in water loss was mainly caused by the decline in needle stomatal conductance. Sorbitol-induced stomatal control was more closely associated with reduction in plant water potential, rather than increase in abscisic acid concentrations. After rehydration of stressed-plants, most of the preconditioned seedlings with sorbitol were survived, while only 35% of Douglas-fir and 28% of Western hemlock seedlings treated with water were alive. The post-growth was significantly greater in the preconditioned seedlings than only water-treated seedlings. These results suggested that the earlier stomatal control with sorbitol-facilitated preconditioning could play a role in improving desiccation resistance of evergreen woody plants at transplanting in the field where water supply is limited or dry conditions are prevailing.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.38-45
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• 2007

Flakeboards made from ring- and drum-cut flakes of Douglas-fir, hemlock, red lauan and kapur using two kinds of resin levels were evaluated for the selected properties according to flake thickness. The pH and buffering capacity of four species were determined. Those of kapur were extremely different from the other three species. These pH and buffering capacity values result in the poor internal bond strength of kapur flakeboard. The internal bond strength was affected significantly by flake thickness, resin content and species. MOR and MOE in bending strength were maximized at medium drum-cut flake thickness. Screw holding strength was not consistent for flake thickness, but it was influenced by species. Thickness swelling and water absorption of Douglas-fir and hemlock flakeboard were minimized at medium drum-cut flake thickness.

• Journal of the Korean Wood Science and Technology
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• v.37 no.5
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• pp.459-464
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• 2009

This study was conducted to find the relationship between the moisture content and basic density of green lumber and the final moisture content of kiln dried lumber. The possibility of using a ultrasonic nondestructive testing technology was investigated. Four matched 2-foot long boards were kiln-dried for 12, 24, 36 and 48 hours. Twenty three slices were cut to examine the distribution of moisture content along the length. It was revealed that the green weight was a better estimator of the final moisture content of the kiln-dried board than the green moisture content. The standard deviations of the moisture contents of the slices were not correlated with the final moisture contents of the kiln-dried boards. The two ultrasonic devices used for this study were apparently good tools for NDT.

• Journal of the Korean Wood Science and Technology
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• v.29 no.3
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• pp.27-35
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• 2001

Four different sources of wood-fibers from Eucalyptus, Italian poplar, hemlock, and mixed species fibers were used to study the influence of their fiber characteristics on the performance of medium density fiberboard (MDF) panels bonded with both urea-formaldehyde (UF) and phenol-formaldehyde (PF) adhesives. Included fiber characteristics were fiber length, size distribution, bulk density, and acidity. Physical and mechanical properties of MDF panels manufactured by dry process using these different fibers were determined for the comparison of board performance. Two hardwood species had a large fraction of short fibers resulting in a higher bulk density while very long hemlock fibers had lower bulk density. Fiber acidity was revealed to strongly affect the internal bond (IB) strength of MDF panels bonded with UF resins. MDF panels made from mixed species fibers showed highest IB strength of all panels prepared. UF-bonded MDF panels showed poor dimensional stability. In conclusion, the present study showed that wood-fiber characteristics such as fiber length, bulk density, and acidity affect the performance of MDF boards, and also suggested that fiber characteristics be considered for MDF panel manufacture.

• Journal of the Korean Wood Science and Technology
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• v.29 no.1
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• pp.1-8
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• 2001

Red pine (Pinus densiflora), white pine (Pinus koraiensis), larch (Larix leptolepis) and Western hemlock (Tsuga heterophylla) lumber were vacuum-press dried under three drying schedules to investigate current moisture contents (MC), drying rates and drying time factors related to five lumber thicknesses of 3, 5, 7, 9 and 11cm. Current MC could be estimated by drying factors such as lumber thickness, initial Me and drying time. Average drying rate from 30% to 15% Me was the highest for Western hemlock below fiber satuartion point, red pine, white pine and larch in the order of their magnitude. Drying rate curvilinearly decreased as lumber thickness increased. Drying time factor curvilinearly increased as lumber thickness increased.