• Journal of the Korean Wood Science and Technology
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• v.12 no.2
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• pp.20-26
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• 1984

This study was carried out to investigate the influence of chemical type and its retention in the fire-retardant treated plywoods on the static bending strength, a property peculiar to plywood. Being soaked in 20% aqueous solution of $(NH_4)_2SO_4$, $NH_4H_2PO_4$, $(NH_4)_2HPO_4$. Borax-Boric acid and Minalith for 3 to 12 hours at three-hour intervals and redried at $120^{\circ}C$ in hot press, the treated plywoods were put to static bending test. The values of chemical treated plywoods in Stress at proportional limit, Modulus of elasticity, Modulus of rupture and Work per unit volume to proportional limit were widely higher than those of water treated plywoods(control) and Borax-Boric acid treatment showed the highest value in the four mechanical data. And the bending strength of fire-retardant treated plywoods increased with the extension of soaking time or the increase of chemical retention in themselves. Borix-Boric acid was the desirable fire-retardant for thin plywood in view of mechanical strength and soaking defects in this study.

• Journal of Korean Society of Forest Science
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• v.98 no.4
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• pp.417-425
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• 2009

This study analyzed core issues addressed in the tentative agreement of WTO ministerial meetings held to finish WTO/DDA negotiations in Geneva in July 2008. The objectives of this study are to analyze changes in tariff reduction on timber products, and their influence on demand and supply of the items according to the modality of Non-Agricultural Market Access (NAMA) and to provide basic information for strategy formulation of our country for further WTO/DDA negotiations. The results indicate that there will not be significant changes in the tariff on sawnwood and on veneer sheets, however, the tariff on plywood need to be cut by around 50% from the applicable tariff rates of 2008 on condition that our country is in the position of developed countries. Therefore, the item of plywood is expected to be influenced greatly according to the change in tariff reduction. From the analysis of influence of tariff reduction on the demand and supply of timber products including sawnwood and wood based panels, such as plywood, particleboard, and fiberboard, the import quantities of the items are expected to be changed from 0.8% to 13.3% if our country is in the position of developed countries, however, they are expected to decline by 0.8%~44.3%, if our country is in the position of developing countries (22, coefficient for developing members).

• Fire Science and Engineering
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• v.29 no.4
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• pp.49-56
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• 2015

Toxic gases from five types of interior building materials were investigated according to Naval Engineering Standard (NES) 713. The materials were plywood, indoor wall coverings (wood wall plate members and pine wood), reinforced Styrofoam insulation, laminate flooring, and PVC. Specimens were measured using an NES 713 toxicity test apparatus to analyze the hazardous substances in combustion gas from the materials. We used the US Department of Defense standard (MIL-DTL, Military Standard) to calculate the toxicity index of the combustion gas. Emissions of $CO_2$ from all specimens did not exceed the NES 713 limit of 100,000 ppm. The amount of CO gas emissions from reinforced Styrofoam insulation was 6,098 ppm. 25 ppm and 49 ppm of formaldehyde were released from the reinforced Styrofoam insulation and PVC flooring, respectively. These values were less than the limit of 400 ppm. The highest emissions were from $NO_X$ emitted by plywood and were above the limit of 250 ppm. The toxicity index of the specimens were calculated as 5.19 for plywood, 4.13 for PVC flooring, 2.35 for reinforced Styrofoam insulation, 2.34 for laminate flooring, and 1.22 for indoor wall coverings (pine wood). Our research helps us to understand the properties of these five interior materials by analyzing the combustion gas and explaining the toxicity of constituents and the toxicity index. Also, it would be useful for giving fundamentals to guide the safe use of interior materials for applications.

• Journal of the Korean Wood Science and Technology
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• v.12 no.4
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• pp.12-18
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• 1984

Soaking treated in 20% aqueous solutions of $(NH_4)_2SO_4$, $NH_4H_2PO_4$, $(NH_4)_2HPO_4$, $Na_2B_4O_7-H_3BO_3$(60:40) and Minalith, the mixed salts for 9 hrs. the wet 3.5mm meranti (Parashorea spp.) plywoods were press-dried at 90, 120 and $150^{\circ}C$ and put to static bending test to examine the influence of redrying temperature on the strength of fire-retardant treated plywoods ill flexure. While water-soaking treatment (control) showed serious reduction in Stress at proportional limit, MOE, MOR, Work per unit volume at $150^{\circ}C$, all the fire-retardant treatments maintained bending strength even at $150^{\circ}C$ and showed rather increased values in case of some chemicals. In view of drying rate and maintenance of strength, the most pertinent platen temperature was $150^{\circ}C$ and Borax-Boric acid was the predominant fire-retardant in this study.

• Journal of the Korean Wood Science and Technology
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• v.11 no.1
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• pp.12-17
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• 1983

The shear strength of plywoods using Douglus-fir bark powder and particlebard sander dust(PSD), abandoned materials in plywood and particleboard industries, as extender to UF resin, was compared with that of plywoods using wheat flour. Extenders were mixed at the rate of 0%, 5%, 10%, 20%, and 30% of UF resin weight. In obtained results, the dry shear strength of all extended plywoods was highest at extending ratio 5% and the wet shear strength was highest at no extending and 5%. Douglas-fir bark powder-and PSD-extended plywoods had as high dry and wet shear strength as wheat flour-extended plywoods up to extending ratio 10% and 20% respectively. But at 300%, wheat flour-extended plywoods had higher shear strength. Douglas-fir bark powder and PSD size should have been reduced (enough to pass through 325 mesh screen) in order to develop the satisfactory mixing, spreading and plywood bond quality. But in this study the powders to pass through 100 mesh screen were used.

• Journal of the Korean Wood Science and Technology
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• v.27 no.3
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• pp.39-50
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• 1999

This research was carried out to investigate the development of fire-retardancy treatment technology and performance evaluation of fire-retardant treated plywoods. Radiata pine, keruing, dillenia, calophyllum and terminalia veneers were treated by normal(conventional) pressure soak(NPS) and vacuum-pressure-soak(VPS) using 20% water solution of diammonium phosphate. Then, 4.8mm thick, 3ply plywoods were fabricated with combination of fire-retardant treated, untreated or water-immersion types and several composition types of radiata pine and keruing veneers, i,e. the uniform and the mixed types in species composition, and the homogenious and the alternate layer types in veneer treatment. In composed species, the retention and the treatment effects of fire-retardant chemicals III radiata pine was still greater than those of keruing. The effect of VPS treatment was larger than that of NPS treatment, however, adhesive bonding strength and bending strength of plywoods treated by these two methods were not necessarily lowered, compared to those of untreated plywood. And also, fire endurance performance of the urea melamine resin-bonded plywood was greater than that of the phenol resin-bonded plywood. In result, the appropriate combination in veneer species and layer as well as alternate fire-retardant treatments would be more efficiently available in service.

• Journal of the Korean Wood Science and Technology
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• v.9 no.3
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• pp.16-23
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• 1981

This study has been carried out to make a comparative study for the adhesive control methods specifically developed for application to formaldehyde. The method for formaldehyde determination used in this report is the improved chromo tropic acid determination. The results are summarized as follows: 1. The soaking treatment in aqueous solution of urea wok the most scavenging effect on the formaldehyde release from a plywood sample glued with a urea formaldehyde adhesive, and other removal treatment such as resorcinol, albumine-, and hardener-treatment gave significant reduction too. 2. In glue shear strength of dry test, 2% of resorcinol treatment and soaking treatment showed the highest strength and all the other treatment met the standard, but in hot water soaking test, 2% of resorcinol treatment gave the best results, on the other hand, adding the hardener showed the lowest strength and failed in meeting the standard. 3. Air dried moisture content of all treated plywood met the standard which calls for 13% or bellow. 4. In this comparative study, we can make a strong combination each other or go into the details of one treatment for the best result through the more study.

• Journal of the Korean Wood Science and Technology
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• v.41 no.6
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• pp.490-496
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• 2013

The board using recycled wood waste chip tends to decrease in terms of physical and mechanical properties. The reasons are notably different shape of chips, components of used adhesive and impurity content, which bring the irregular quality and downgrading of board. More over, the board has higher emissivity of formaldehyde than regular board, because recycled chip contains adhesives that were used to make previous products. This low quality of products weakens the price and quality competitiveness, and it led to bringing the issue of problem in Korean board industry. For these reason, in this study, boards using byproducts of plywood were made to evaluate physical and mechanical properties according to manufacturing conditions. As a result, The board was consists of 4~16 mesh chips for core layer and veneer on both face and they were combined using EMDI, and its' bending strength was 57.7 $N/mm^2$ which is 215% higher than that of OSB (26.8 $N/mm^2$). Moreover, the emissivity of formaldehyde was 0.7 ppm, this board seems to substitute OSB for rated sheathing.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.65-71
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• 2003

In this paper, bending capacities of glulams with different configurations of cross-section were evaluated. These configurations included horizontal(BH), vertical(BVN), vertical with vertical plywood (BVV) and vertical combination of lamination with horizontal plywood(BVH). Full-scale bending tests were performed to investigate the effect of different section configurations on bending strength(MOR) and stiffness(MOE) of glulam. Compared with type BH, MOR of glulam with type BVN configuration was improved about 23%, which was considered to be caused by defect dispersion effect, while MOE of glulams with these two types of configurations were similar. Because MOE of plywood is generally smaller than that of solid wood laminar, MOE of type BVH glulam decreased about 15%, but in the case of type BVV glulam, MOR was improved without any reduction of MOE. The reason of this result could be undersood in the view of shear-reinforcement effect, which was verified from analysis of fracture mode. From the results of this study, it was concluded that bending capacity of glulam could be improved by proper section design, such as laminar arrangement and shear reinforcement.

• Proceedings of the Korea Forestry Energy Research Society Conference
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• 2011.02a
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• pp.112-115
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• 2011