• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.58-66
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• 2007

The objective of this research was to develop environment-friendly adhesives for face fancy veneer bonding of engineered flooring. Urea-formaldehyde (UF)-tannin and melamine-formaldehyde (MF)/PVAc hybrid resin were used to replace UF resin in the formaldehyde-based resin system in order to reduce formaldehyde and volatile organic compound (VOC) emissions from the adhesives used between plywoods and fancy veneers. Wattle tannin powder (5 wt%) was added to UF resin and PVAc (30 wt%) to MF resin. These adhesive systems showed better bonding than commercial UF resin with a similar level of wood penetration. The initial adhesion strength was sufficient to be maintained within the optimum initial tack range. The standard formaldehyde emission test (desiccator method) and VOC analyzer were used to determine the formaldehyde and VOC emissions from engineered flooring bonded with commercial UF resin, UF-tannin and MF/PVAc hybrid resin. By desiccator method, the formaldehyde emission level of UF resin showed the highest but was reduced by replacing with UF-tannin and MF/PVAc hybrid resin. MF/PVAc hybrid satisfied the $E_1$ grade (below $1.5mg/{\ell}$). VOC emission results by VOC analyzer were similar with the formaldehyde emission results. TVOC emission was in the following order: UF > UF-tannin > MF/PVAc hybrid resin.

• Journal of the Korean Wood Science and Technology
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• v.34 no.2
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• pp.37-45
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• 2006

The viscoelastic properties of blends of melamine-formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) for engineered flooring used on the Korean traditional ONDOL house floor heating system were investigated by dynamic mechanical thermal analysis (DMTA). Because MF resin is a thermosetting adhesive, the effect of MF rein was shown across all thermal behaviors. The addition of PVAc reduced the curing temperature. The DMTA thermogram of MF resin showed that the storage modulus (E') increased as the temperature was further increased as a result of the cross-linking induced by the curing reaction of the resin. The storage modulus (E') of MF resin increased both as a function of increasing temperature and with increasing heating rate. From isothermal DMTA results, peak $T_{tan{\delta}}$ values, maximum value of loss modulus (E") and the rigidities (${\Delta}E$) of MF/PVAc blends at room temperature as a function of open time, peak $T_{tan{\delta}}$ and maximum loss modulus (E") values were found to increase with blend MF content. Moreover, the rigidities of the 70:30 and 50:50 MF/PVAc blends were higher than those of the other blends, especially of 100% PVAc or MF. We concluded that blends the MF/PVAc blend ratios correlate during the adhesion process.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.24-37
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• 2007

The Korean Ministry of Environment started controlling indoor air quality (IAQ) in 2004 through the introduction of a law regulating the use of pollutant emitting building materials. The use of materials with formaldehyde emission levels above $1.25 mg/m^2{\cdot}h$ (JIS A 1901, small chamber method) has been prohibited. This level is equivalent to the $E_2$ grade ($>5.0mg/{\ell}$) of the desiccator method (JIS A 1460). However, the $20{\ell}$ small chamber method requires a 7-day test time to obtain the formaldehyde and volatile organic compound (VOC) emission results from solid building interior materials. As a approach to significantly reduce the test time, the field and laboratory emission cell (FLEC) has been proposed in Europe with a total test time less than one hour. This paper assesses the reproducibility of testing formaldehyde and TVOC emissions from wood-based composites such as medium density fiberboard (MDF), laminate flooring, and engineered flooring using three methods: desiccator, perforator and FLEC. According to the desiccator and perforator standards, the formaldehyde emission level of each flooring was ${\le}E_1$ grade. The formaldehyde emission of MDF was $3.48 mg/{\ell}$ by the desiccator method and 8.57 g/100 g by the perforator method. To determine the formaldehyde emission, the peak areas of each wood-based composite were calculated from aldehyde chromatograms obtained using the FLEC method. Formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde were detected as aldehyde compounds. The experimental results indicated that MDF emitted chloroform, benzene, trichloroethylene, toluene, ethylbenzene, m,p-xy-lene, styrene, and o-xylene. MDF emitted significantly greater amounts of VOCs than the floorings did.

• Advances in aircraft and spacecraft science
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• v.3 no.1
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• pp.15-28
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• 2016

Although the aircraft industry was the first to use fibre composites, now they are increasingly used in a range of structural applications such as flooring, decking, platforms and roofs. Interlayer delamination is a major failure mode which threatens the reliability of composite structures. Delamination can grow in size under increasing loads with time and hence leads to severe loss of structural integrity and stiffness reduction. Delamination reduces the natural frequency and as a consequence may result in resonance. Hence, the study of the effects of delamination on the free vibration behaviour of multilayer composite structures is imperative. The focus of this paper is to develop a 3D FE model and investigate the free vibration behaviour of fibre composite multilayer sandwich panels with interlayer delaminations. A series of parametric studies are conducted to assess the influence of various parameters of concern, using a commercially available finite element package. Additionally, selected points in the delaminated region are connected appropriately to simulate bolting as a remedial measure to fasten the delamination region in the aim of reducing the effects of delamination. First order shear deformation theory based plate elements have been used to model each sandwich layer. The findings suggest that the delamination size and the end fixity of the plate are the most important factors responsible for stiffness reduction due to delamination damage in composite laminates. It is also revealed that bolting the delaminated region can significantly reduce the natural frequency variation due to delamination thereby improving the dynamic performance.

• Journal of the Korea Furniture Society
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• v.22 no.3
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• pp.219-229
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• 2011

Sick building syndrome symptoms that are experienced by building occupants may be caused by toxic substances such as formaldehyde and VOCs, which are known to be emitted from building materials and wood composite products such as wood-based panel, furniture, engineered flooring and construction adhesive. In Korea, the use of wood composite products for indoor environments has increased over the last decade. Recently, wood composite products have been installed in approximately 95% of newly constructed residential buildings. The use of these products has resulted in problems related to human health, and consequently a realization about the importance of indoor air quality. In addition, consumer demand is increasing for natural materials because conventional building materials and wood composite products are made by adding urea-formaldehyde resin or they contain formaldehyde-based resin. More recently, many efforts have been made to reduce formaldehyde emission from building materials that laid in the indoor environment. Especially, if conventional formaldehyde-based adhesives are replaced with green adhesives for residential spaces, it is possible to reduce most of the emission amounts of formaldehyde in indoor environments. In line with this expectation, many researches are being conducted using natural materials such as tannin and cashew nut shell liquid (CNSL). This study discussed the affects and possibilities of green adhesives to reduce formaldehyde emission in indoor environments.