• Journal of the Korean Wood Science and Technology
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• v.34 no.4
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• pp.31-36
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• 2006

This study was conducted to improve the bond strength of plywood bonded with F/U molar ratio urea-formaldehyde (UF) resins modified with the selected FGMDI prepolymer contents for various purposes. The amount of FGMDI was mixed with liquid UF resin at 0 wt% (as control), 2 wt%, 5 wt%, 10 wt%, 25 wt%, and 50 wt% based on the resin solids. As results, in bonding strength, plywood with F/U molar ratio of 1.4 showed the highest value in Type 2 test and all molar ratio UF resins modified with over 25 wt% of the FGMDI showed more than $11kgf/cm^2$, which was satisfied the minimum requirement of KS standard, $7.5kgf/cm^2$, after Type1.5 testing. As F/U molar ratio was increased and the FGMDI addition in the UF resin was increased, average reduction rate of Type 1.5 bonding strength compared with Type 2 was significantly decreased.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.11-18
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• 2009

The purpose of this study is to examine a proper amount of addition and a proper point for addition of titanium dioxide for the manufacture of E0 type of urea-formaldehyde resin (UF). The reduction of free formaldehyde from UF resin treated particle board was also investigated. $TiO_2$ content was 0.5%, 1% and 3% on the dry basis of UF resin. UV light was used to initiate reaction. The results of this study are as follows: 1. During UF resin manufacturing process, the second adding step of urea was proper point for $TiO_2$ addition. 2. 1 % addition of $TiO_2$ gave good values for the Eo type urea-formaldehyde resin. 3. There was no significant difference between physical properties of particle board, but the higher the adding content of titanium dioxide resulted in the lower the mechanical properties.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.277-281
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• 2019

The objective of this research is to evaluate the effect of adhesive types on dimensional stability of bamboo-oriented particleboard. The materials used in this research are bamboo tali(Gigantochloa apus J.A & J.H. Schult. Kurz), UF/MDI(8, 10, 12 % level), and MF, MDI, and PF at 7 % level. Particle and adhesive are mixed using a blending machine; then, mat forming and hot pressing processes are performed using adhesive-suitable temperature and time references. MDI resin is set at $160^{\circ}C$ temperature for 5 minutes. PF resin and MF resin are pressed at $170^{\circ}C$ for 10 minutes, and $140^{\circ}C$ for 10 minutes, respectively, while UF/MDI sets at temperature of $140^{\circ}C$ for 10 minutes. The results show that particleboard using PF resin produces the lowest thickness swelling value. The particleboard using UF/MDI resin also produces good response for thickness swelling value. Interesting things happen in that UF/MDI adhesive produces a thickness swelling value better than that of MDI resin. FTIR analysis on particleboard bonded by UF/MDI resin combination shows the presence of carbonyl group C=O vibration on multi substitution of urea at wave number of around $1,700cm^{-1}$.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.471-481
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• 2017

As the molecular weight (MW) of urea-formaldehyde (UF) resins had a great impact on their properties, this work was conducted to study effect of analytical parameters of gel permeation chromatography (GPC) on the MW measurement of UF resins. GPC parameters such as flow rate, column, detector temperature, and sample injection temperature were selected to compare number-average molecular weight (Mn), weight-average molecular weight (Mw), molecular weight distribution (MWD) and polydispersity index (PDI) of two UF resins with different viscosities. As expected, UF resin with higher viscosity resulted in greater Mn and Mw than those of low viscosity UF resin. When the flow rate increased, both Mn and Mw of UF resins decreased and MWD became narrower. By contrast, both Mn and Mw increased and MWD became wide when the column, detector, and sample injection temperature increased. The column, detector, and sample injection temperature of $50^{\circ}C$ at a flow rate of $0.5m{\ell}/min$ resulted in the highest MW and broadest MWD for the GPC analysis. These results suggest that the apparent molecular size or a hydrodynamic radius of UF resin molecules dissolved in the mobile phase affect to Mn, Mw and MWD.

• Journal of Adhesion and Interface
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• v.13 no.2
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• pp.85-88
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• 2012

In this paper, the curing reaction of UF resins was investigated by a real time FT-IR method. The curing temperature range of the UF resin was $25{\sim}200^{\circ}C$. It was found that the reactions of UF resin at different temperatures resultedin resins with different cross-linked structures. A real time FT-IR spectroscopy can be considered as a good routine analytical tool for following the progress of UF resin curing.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.42-51
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• 2006

The this study, the effect of rice husk flour (RHF) as scavenger on formaldehyde emission rate and formaldehyde content from urea-formaldehyde (UF) resin bonded RHF content wood particleboards (PB). Two type of particle size ($30{\mu}m$ and $300{\mu}m$) of RHF was premixed with the UF resin at 5% and 15% by weight. The performance of UF resins is greatly influenced by the curing characteristics in their curing processing. The curing behavior was monitored activation energy ($E_a$) by DSC and pH variation according to RHF contents. PB with dimensions of $27cm{\times}27cm{\times}0.7cm$ was prepared at a specific gravity of 0.75 using $E_1$ and $E_2$ class UF resins. Formaldehyde emission and formaldehyde content from RHF filled PB bonded with UF resin was measured by 24 h desiccator and perforator method, respectively. RHF causes an increased pH of UF resin. $E_a$ of the modified UF resin decreased independently of RHF particle size. As the pH and the $E_a$ variation of the UF resin containing RHF increased, the amount of formaldehyde content decreased. The formaldehyde emission and formaldehyde content levels of the PB bonded with 15 wt% of $30{\mu}m$ RHF and $E_2$ type UF resin were low and satisfied grade $E_1$, as measured by 24 h desiccator and perforator method. The result of a comparison between 24 h desiccator and perforator test using PB showed that the linear regression analyses show a good correlation between the results for the 24 h desiccator and the perforator tests. The linear regression of a correlation between the desiccator and the perforator was Y=4.842X-0.064 ($R^2=0.989$). RHF was effective at reducing formaldehyde emission and formaldehyde content in urea-formaldehyde adhesives when used as scavenger.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.2
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• pp.13-26
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• 1985

In this study, when cotton fabrics dyed with Direct dyes are treated under various resin concentration 2, 4, 8, 12, $14\%$ with ureaformaldehyde(UF) and melamineformaldehyde(MF) resin which can be imparted the crease recovery to textiles, chang of properties on lightfastness, washfastness, crease recovery, breaking strength, etc. and color changes are investigated. the results are as follows 1) Color difference(${\Delta}$E) increased but K/S value decreased according to the increase of resin cone. such tendency showed that MF treated fabrics and soaping fabrics were evident than UF treated fabrics and non-soaping fabrics. 2) In lightfastness, ${\Delta}$E and K/S value of resin treated fabrics were reduced as compared with untreated fabrics according to the increase of resin cone. The lower ${\Delta}$E and K/S value of MF than ${\Delta}$E and K/S value of UF showed low lightfastness of MF. pH of resin treted fabrics was almost unaffected with lightfastness. 3) In washfastness, ${\Delta}$E and K/S value of resin treated fabrics decreased slightly as com-pared with untreated fabricsaccording tothe increase of resin cone. The ${\Delta}$E and K/S value of MF decreased lower than UF. But in the case of the higher resin cone. than about $8\%$, they were not almost differentiated. 4) As resin cone. increased, crease recovery considerably increased but breaking strength and elongation decreased. The fabrics treated with UF were good crease recovery, whereas the fabrics treated with MF were good breaking strength. 5) Soaping appeared to improve the lightfastness, washfastness, crease recovery but appeared to work adverse effect on breaking strength.

• Journal of the Korean Wood Science and Technology
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• v.31 no.1
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• pp.22-26
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• 2003

Particleboards (PBs) were made from Pinus densiflora thinning particle with urea-formaldehyde (UF) resin added casein and soybean as extender. The performance test results of the PB made showed that Pinus densiflora thinning log was suitable raw material for PB. As the extender addition in the UF resin was increased, the mechanical performance of the PB, bonded with the extended UF resin, were significantly decreased. However, casein and soybean can be used up to 15% and 20% of the UF resin solids respectively.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.29-39
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• 2005

Formaldehyde emissions from wood-based panels bonded with pine and wattle tannin-based adhesives, urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), and co-polycondensed resin of urea-melamine-formaldehyde (UMF) were measured by the Japanese standard method using a desiccator (JIS A 1460) and the EN 120 (European Committee For Standardization, 1991) method using the perforator value. In formaldehyde emission, all particleboards made using the wattle tannin-based adhesive with three different hardeners, paraformaldehyde, hexamethylenetetramine, and tris(hydroxyl)nitromethan (TN), satisfied the requirements of grade $E_1$. But only those made using the pine tannin-based adhesive with the hexamine as hardener met the grade $E_1$ requirements. Hexamine was effective in reducing formaldehyde emission in tannin-based adhesives when used as the hardener. While the UF resin showed a desiccator value of $7.1mg/{\ell}$ and a perforator value of 12.1 mg/100 g, the MF resin exhibited a desiccator value of $0.6mg/{\ell}$ and a perforator value of 2.9 mg/100 g. According to the Japanese Industrial Standard and the European Standard, the formaldehyde emission level of the MDF panels made with UF resin in this study came under grade $E_2$. The formaldehyde emission level was dramatically reduced by the addition of MF resin. The desiccator and perforator methods produced proportionally equivalent results. Gas chromatography, a more sensitive and advanced method, was also used. The samples for gas chromatography were gathered during the experiment involving the perforator method. The formaldehyde contents measured by gas chromatography were directly proportional to the perforator values.

• Journal of Sericultural and Entomological Science
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• v.27 no.2
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• pp.47-53
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• 1985

The studies on the reaction of Urea-Formaldehyde(UF) resin with silk fabric were studied, and the final results summarized as below; 1. The pH and UF molar ratio for preparing liquid resin was found at pH 4-5 and UF molar ration 1:2 and above. 2. The weight gains were increased with respect to increase in concentration of UF resin solution, while moisture regains were decreased. 3. The weight gains were significant high in case of wet pick up 70%. 4. The weight gains were increased with respect to increase in curing temperature and the amount of catalyst((NH4)2SO4) found was 2.5% on the weight of Dimethylol urea and Hydrochloric acid was 1%, Tartaric acid was 10%. 5. The effect of different catalyst on wash fastness of UF resin was good where as in case of acidic catalyst was significantly high. 6. The weight gains with different catalyst was high where as in case of potential acid catalyst was significantly high. 7. The crease recovery are increased with the increase of the weight gain of silk fabric and also stiffness are increased.