• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.20-27
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• 1994

Water repellent preservative (WRP) treated and untreated, small-sized specimens prepared from semiwater resistant, water resistant, and tegofilm-overlaid plywood were exposed to outdoor weathering for one year. Exterior durability of specimens was evaluated on the basis of changes in dynamic modulus of elasticity, degree of delamination, modulus of elasticity, modulus of rupture, and glueline shear strength. Among untreated specimens, tegofilm-overlaid plywood showed the best outdoor durability, and durability between semiwater resistant and water resistant plywood was similar. Although WRP treatment increased the durability of all types of plywoods, the effect of treatment on the increase in durability for semi water resistant plywood was not distinct. Accordingly, it can be concluded that semi water resistant plywood, which is used for temporary construction such as concrete formwork in our country, can not be inadequate for exterior use, regardless of WRP treatment. The bending strength and glueline shear strength of untreated water resistant plywood measured after weathering for one year did not exceed the minimum value specified by Korean Standard (KS), thereby the outdoor use of water resistant plywood was not desirable without WRP treatment. Exterior durability between treated water resistant plywood and untreated tegofilm-overlaid plywood was very similar. This result suggests that if an exposed plywood surface is treated with WRP regularly water resistant plywood can be used for temporary construction. This suggestion, however, needs to be investigated. In summary, semiwater resistant plywood cannot be used for temporay construction regardless of WRP treatment. Water resistant plywood can be used only with WRP treatment. Comparing the cost of tegofilm-overlaid plywood to costs of water resistant plywood and WRP treatment, however, it can be concluded that use of tegofilm-overlaid plywood for temporay constrution is strongly suggested from the point of view of both outdoor durability and costs.

• Journal of the Korean Wood Science and Technology
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• v.20 no.1
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• pp.46-50
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• 1992

본 연구는 잣나무 간벌재를 이용한 plywood gusset plate 접합과 toothed metal plate 접합에 대하여 인장력을 가해 조사하였다. plywood gusset plate 접합에 있어서는 합판과 부재 사이를 상온 경화제(초산 비닐 수지)로 접착한 후 6d 못으로 접합한 형태와 단지 합판만을 사용한 형태의 plywood gusset plate 접합 사이의 기계적 특성 차이를 조사했다. toothed metal plate 접합은 plywood gusset plate 접합보다 인장력에서 좋은 behavior를 보였다. 또한 접착제를 가한 plywood gusset plate 접합은 접합제를 가하지 않은 형태보다 큰 하중 지지력을 보였다.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.165-165
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• 1982

In order to improve decaying properties of the plywood, the effectiveness of the Malenit treatment on the shear strength and decaying properties of the plywood has been investigated. The results are as follows. 1. No decrease of the shear strength of the plywood has shown despite of plywood treatment with Malenit right after plywood made or veneer treated with the same preservative prior to plywood manu. factured. 2. The effectiveness of Malenit treatment on decaying property of the plywood has shown much greater than that of the untreated plywood and red pine sapwood. 3. Weight decreases of the test specimens due to the infection of the different fungi have seen in different ways. If fungi infected weight decreases of the specimens are different in it's degree due to the fungi.

• Journal of the Korean Wood Science and Technology
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• v.4 no.1
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• pp.38-47
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• 1976

This study was carried out to exploit and utilize American sycamore (Platanus occidentalis) and poplar grown in Korea as veneer species for plywood manufacture. At this study to save the imported lauan logs and dollars, the effects affecting to the properties of plywood constructed by sycamore, poplar and lauan veneers were studied. Important items dealt with this study were dry and wet shear strength, moisture content, and specific gravities By the results and discussion it may be summarized as followings. 1) Sycamore core lauan plywood (A-II type) was shown best dry shear strength, and the next were all lauan veneer plywood (A-I type), poplar core lauan plywood (B-I type), lauan core sycamore plywood (A-III type) in order. There are no differences between dry shear strength of A-II type and A-I type, A-II type and B-I type plywood. 2) Wet shear strength showed the same order with dry shear strength. A-II type plywood showed best wet shear strength and it showed more difference than other plwoods. A-I type, B-I type and A-III type plywood were all very good without significant difference in wet shear strength. 3) B-I type plywood showed highest moisture content of all type plywood and the next were all sycamore(A-IV type) all poplar plywood (B-III type), A-III type, B-II type, A-II type pllywood in order. Generally high moisture content showed when two or three veneers were same species in the three layer plywood. 4) A-III type plywood showed highest specific gravity of all and the next was A-IV type plywood without a difference to A-I type plywood on the whole. plywoods constructed by lauan and sycamore were shown high specific gravities and the next was lauan, sycamore and poplar, lauan and poplar. It seemed to be that connected wi th the specific gravity of veneer itself in different species. 5) The plywood manufactured by extension of potato flour is not only superior but also profitable in the price aspect than the plywood manufactured by extension of wheat flour.

• Journal of the Korean Wood Science and Technology
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• v.26 no.2
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• pp.6-15
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• 1998

A total of forty five-ply, 30- by 30-cm lauan and larch plywood sheets were manufactured in the laboratory using commercial urea and phenol resin adhesives; half of these sheets were treated with fresh concrete. Each sheet was carbonized for 2, 4, and 6hours at $400^{\circ}C$, $600^{\circ}C$, and $750^{\circ}C$, respectively, and their physical properties were measured. The yie1d of charcoal decreased as carbonization temperature and time increased. Charcoal yield was greater in plywood than in veneer, and slightly greater in plywood treated with concrete compared to untreated plywood. Plywood manufactured with phenol resin adhesive had higher pH, higher equilibrium moisture content (EMC), and greater adsorption of methylene-blue dye compared to plywood manufactured with urea resin. For concrete-treated plywood, pH was greater than 10 even when the sheets were carbonized for 2hours at $400^{\circ}C$. Although the EMC of the phenol resin plywood was higher than that of the urea resin plywood, EMC of the phenol resin was lower than that of the urea resin. The larch phenol resin plywood that was carbonized for 6 hours at $750^{\circ}C$ adsorbed more methylene-blue than did the commercia1 wood-based activated charcoal as a result of total pore volume and surface area.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.24-28
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• 2005

Monte Carlo simulation was performed on theoretical models of plywood warp for southern yellow pine plywood originating from the United States. The objective of the investigation was to determine which plywood layers was more warp sensitive to veneers that were manufactured to an undesired thickness. This study found that for a balanced panel (a panel of equal target thickness for each of five layers) manufactured veneers of undesired thickness would experience minimal warp. The veneers of undesired thickness placed in the center of the plywood panel also provided a minimum change of plywood warp properties. The panel warp was very sensitive to surface veneers constructed with undesired thickness. Conversely, this study confirms that monitoring of veneer thickness and proper allocations within the plywood lay-up were critical.

• Journal of the Korean Wood Science and Technology
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• v.24 no.2
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• pp.42-45
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• 1996

A residue from the newsprint waste was investigated as a filler in adhesive for bonding southern pine plywood. The residue was prepared by drying the wet residue to 8% moisture content and grinding the dry material using a laboratory Wiley mitt with a 75-${\mu}m$(200-mesh) screen. The residue was compared to a commercial filler commonly used in structural plywood adhesives. A total of 48 three-ply panels. 12.7mm nominal thickness and 0.3 by 0.3 m in size, were fabricated at two press times(4 and 5 min) and three assembly times(20, 40 and 60 min). Evaluations of the residue were carried out by performance tension shear tests after two 4-hour boil accelerated aging tests on plywood. The test results included tension shear strength and estimated wood failure values. All plywood made with the residue filler were comparable to the control-bonded plywood. These results indicate that residue from the newsprint waste streams would be suitable as filler for plywood adhesives.

• Journal of Korean Society of Forest Science
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• v.30 no.1
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• pp.8-18
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• 1976

This study was carried out to exploit and utilize the exotic American Sycamore(Platanus occidentalis) grown in Korea as a veneer species for plywood manufacture. At present most parts of veneer Legs used in Korea were depended entirely upon the gonus Shorea woods(lauan logs) imported from Southeast Asia region. To decrease manufacturing cost and save imported lauan veneer logs, the effects on properties affecting to the six types of plywood made from proper veneer constructions composed by domestic American Sycamore and imported lauan veneers were compared and discussed. The study has important meanings for the promotion of plywood manufacture by domestic materials. Important items dealt with this study were dry and wet shear strength, moisture contents, specific gravties, and bending strength. By the results and discussions it may be summarized as follows: 1) In dry shear strength platanus(sycamore) core lauan plywood was shown most excellent strong results, and next orders were all lauan plywood, platanus faced lauan plywood, lauan core platanus plywood, lauan faced platanus plywood, and all platanus plywood. There was no difference between platanus core lauan plywood and all lauan plywood, but the differences between those plywoods and the other types of plywood were recognized. 2) In wet shear strength platanus core lauan plywood was shown excellent result the same as dry strength. The difference between platanus core lauan plywood and the other types of plywood was shown, but among the other types of plywood except platanus core lauan plywood were not recognized. 3) The differences among moisture contents according to the veneer construction were not recognized. 4) The plywood constructed by two or more sheets of lauan veneer was shown lower specific gravities than the plywood constructed by two or more sheets of platanus veneer. It is believed that this tendency due to the original specific gravities of veneer before construction. 5) The differences among specific gravities of lauan core platanus plywood, all platanus plywood and lauan faced platanus plywood were not recognized, and like this analyzed result among platanus core lauan plywood, all lauan plywood and platanus faced lauan plywood were not recognized. Accordingly it is believed that the differences are not shown among the plywood constructed by two or more veneers of same species. 6) In bending strength platanus core lauan plywood was shown most excellent values. Next orders were all lauan plywood, platanus faced lauan plywood and the other types of plywood. The differences among the plywood constructed by two or veneers of lauan were shown, but not shown among the plywood constructed by tow or more veneers of platanus.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.152-164
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• 1982

1. In order to make the improvement of plywood quality, this study has been made. The pretreatments applied to the veneers are as follows. a) The soaking treatment of the veneer in 30 percent methanol solution for 24 hours was applied to remove some resinous materials which may cause many stain discolouring on the face of finished plywood. b) The preservative treatment of the veneer in 2 percent malenit solution for 2 to 3 minutes was adopted to make resistance against decay and insect damages. c) The fire retardant treatment of the veneer in 40 percent ammonium phosphate solution for 2 hours was applied to give retardation effect against fire burning. 2. The results summarized in this study are as follows. a) One percent resinous materials was extracted, after the soaking of the veneers in 30 percent diluted methanol. b) No marks of the dirty stains of resinous materials on the face of the treated plywood was shown, although many quite dirty stains on the face of untreated plywood have contrary seen. c) However, the strip shear test strength of the treated plywood was not decreased. It means that there is no difference in the strength between the treated plywood and the untreated plywood. The strength values were 25.08 kg/$cm^2$ and 24.98 kg/$cm^2$, respectively. d) The strip shear test strength of plywood made of the treated veneers in 2 percent malenit solution was not decreased. e) The slight decrease of the strip shear test strength of the treated plywood made of the treated veneer in 40 percent ammonuim phosphate solution was shown. However, the remarkable difference of the fire retardation activities between the treated specimens and the untreated specimens has seen as in Table 10, that is, the fire proofed specimens had taken about 28 seconds to start to burn, while the untreated specimens had taken 15 seconds to reach to burning. This means that the fire retardation effect of the fire proofed plywood was greater than that of the unproofed plywood.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.755-764
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• 2020

Due to pronounced mechanical performance and being environmental friendly, aqueous polymer isocyanate adhesive (API) has been widely applied in the production of formaldehyde-free wood products. In this study, flame retardant formaldehyde-free plywood was prepared by incorporation of flame retardants into the API adhesive. Partially phosphorylated poly (vinyl alcohol) (PPVA) which was prepared by reacting poly (vinyl alcohol) with phosphoric acid was used to replace PVA in API formula. In addition, Mg-Al layered double hydroxides (LDH) was chosen as additive flame retardant, replacing traditional filler CaCO₃ in API adhesive formula. And then, the flame retardant API adhesive with main agent (PPVA replacing PVA70wt.%, SBR emulsion 30wt.%), curing agent 10wt.% (accounts for of the main agent), and 20wt.% LDHs (accounts of the main agent) was used to prepare flame retardant plywood. The effect of application of PPVA and Mg-Al LDH on bonding strength of plywood was investigated. The flammability characteristics of the plywood were determined by cone calorimeter test (CCT). The results revealed that compared with the plywood prepared with API adhesive, the use of PPVA and LDH enhanced the flame retardancy of plywood without negatively affecting bonding strength. The CCT tests indicated that the heat release and smoke production flame retardant API plywood were lower than those of the ordinary API glued plywood. Promising developments for flame retardant API adhesive were expected in future applications of flame retardant formaldehyde-free plywood.