• Macromolecular Research
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• v.14 no.5
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• pp.517-523
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• 2006

The effects of particle content, size and shape on the thermal conductivity (k) and adhesion properties of thermally conductive, pressure-sensitive adhesives (PSAs) were investigated. The matrix resins were thermally crosslinkable, 2-ethylhexyl acrylic polyol and ultraviolet (UV)-curable, random copolymer consisting of acrylic oligomer and various acrylates. We found that k increased with increasing diameter and particle aspect ratio, and was further enhanced due to the reduction of the interfacial thermal barrier when the coupling agent, which increases the adhesion between particles and the matrix resin, was used. On the other hand, adhesion properties such as peel strength and tack of the thermally crosslinkable resin decreased sharply with increasing particle content. However, for UV curable resin, increased particle addition inhibited the decrease in adhesion properties.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.385-394
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• 2017

In this study, reaction mechanism and curing characteristics of adhesives formulated with NaOH- and $H_2SO_4$-hydrolyzed chicken feather (CF) and formaldehyde-based crosslinkers were investigated by FT-IR and DSC. In addition, adhesive properties and formaldehyde emission of medium-density fiberboards (MDF) applied with the adhesives were measured. CF-based adhesives having a solid content of 40% and over were very viscous at $25^{\circ}C$, but the viscosity reduced to $300{\sim}660m{\cdot}Pa{\cdot}s$ at $50^{\circ}C$. Consequently, the adhesives could be used as a sprayable resin. Through the FT-IR spectra of liquid and cured CF-based adhesives, addition reaction of methylol group and condensation reaction between the functional groups with the use of formaldehyde-based crosslinkers were identified. From the analysis of DSC, it was elucidated for CF-based adhesives to require a higher pressing temperature or longer pressing time comparing to commercial urea-formaldehyde (C-UF) resin. MDF bonded with CF-based adhesives, which was formulated with 5% NaOH-hydrolyzed CF (CF-AK-5%) and PF of formaldehyde to phenol mole ratio of 2.5 (PF-2.5), and pressed for 8 min had higher MOR and IB than those with other CF-based adhesives. MOR and IB of MDF bonded with the CF-based adhesives regardless of formulation type and pressing time were higher than those with C-UF resin. When the values compared with the minimum requirements of KS standard, IB exceeded the KS standard in all formulations and pressing time, but MOR of only MDF bonded with CF-AK-5% and PF-2.5 and pressed for 8 min satisfied the KS standard. What was worse, 24-TS of MDF bonded with all CF-based adhesives did not satisfied the KS standard. However, MOR and 24-TS can be improved by increasing the target density of MDF or the amount of wax emulsion, which is added to improve the water resistance of MDF. Importantly, the use of CF-based adhesives decreased greatly the formaldehyde emission. Based on the results, we reached the conclusion that CF-based adhesives formulated under proper conditions had a potential as a sprayable resin for the production of wood panels.

• Journal of the Korean Applied Science and Technology
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• v.32 no.4
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• pp.607-615
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• 2015

To investigate the adhesion effect of various kinds and contents of polymeric methylene diphenyl diisocyanates (pMDIs) on adhesion performance, wood adhesives (A-1~5) were synthesized and characterized. As results, when the amount of pMDI increased in adhesives, the dry tensile strength was found to be proportionally increased sustaining at around $16.0{\sim}21.6kgf/cm^2$. The polyurethane (PU) resin, which used M11S as a source of pMDI showed the best wet tensile strength at $11.9kgf/cm^2$ and cyclic boil tensile strength at $8.1kgf/cm^2$, which satisfied the requirement of over $7kgf/cm^2$. Thermal properties of the rice powder (RP) based polyurethane resins were characterized by differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA). Thermal stability of polyurethane resins increased to $250^{\circ}C$ with adding pMDIs. The more pMDI (M5S) was added to adhesive, the higher thermal stability of the resin was observed by TGA.

• 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.

• The korean journal of orthodontics
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• v.36 no.5
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• pp.360-368
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• 2006

Objective: Surface characteristics of dental materials play an important role in bacterial adhesion. The purpose of this study was to investigate surface characteristics of 5 different light-cured orthodontic adhesives (1 fluoride-releasing composite, 3 non-fluoride-releasing composites, and f resin-modified glass ionomer). Methods: Surface roughness was measured using a confocal laser scanning microscope. Contact angle and surface free energy components were analyzed using the sessile drop method. Results: Surface roughness was significantly different between adhesives despite a relatively small variation (less than $0.05\;{\mu}m$). Lightbond and Monolok2 were rougher than Enlight and Transbond XT. There were also significant differences in contact angles and surface free energy components between adhesives. In particular, considerable differences in contact angles and surface free energy components were found between resin modified glass ionomer and the composites. Resin modified glass ionomer showed significantly smaller contact angles in 3 different probe liquids and had higher total surface free energy and stronger polarity, with notably stronger basic property than the composites. Conclusion: Resin modified glass ionomer may provide a more favourable environment for bacterial adhesion than composite adhesives.

• Restorative Dentistry and Endodontics
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• v.28 no.1
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• pp.23-33
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• 2003

The purpose of this study was to compare in vitro interfacial relationship of restorations bonded with three self-etching primer adhesives and one self-etching adhesive. Class I cavity preparations were prepared on twenty extracted human molars. Prepared teeth were divided into four groups and restored with four adhesives and composites Clearfil SE $Bond/Clearfil^{TM}$ AP-X (SE), UniFil $Bond/UniFil^{\circledR}$ F (UF), FL $Bond/Filtek^{TM}$ Z 250 (FL) and Prompt $L-Pop/Filtek^{TM}$ Z 250 (LP) After storing in distilled water of room temperature for 24 hours, the specimens were vertically sectioned and decalcified. Morphological patterns between the enamel/dentin and adhesives were observed under SEM. The results of this study were as follows : 1. They showed close adaptation between enamel and SE, UF and FL except for LP. 2. The hybrid layer in dentin was $2{\;}\mu\textrm{m}$ thick in SE, $1.5{\;}\mu\textrm{m}$ thick in UF, and $0.4{\;}\mu\textrm{m}$ in both FL and LP. So, the hybrid layers of SE and UF were slightly thicker than that of FL and LP. 3. The lengths and diameters of resin tags in UF and FL were similar, but those of LP were slightly shorter and slenderer than those of SE. 4. The resin tags were long rod shape in SE, and funnel shape in other groups Within the limitations of this study, it was concluded that self-etching primer adhesives showed close adaptation on enamel. In addition, the thickness of hybrid layer ranged from $0.4-1.5{\;}\mu\textrm{m}$ between adhesives and dentin. The resin tags were long rod or funnel shape, and dimension of them was similar or different among adhesives.

• Restorative Dentistry and Endodontics
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• v.32 no.5
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• pp.426-436
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• 2007

The objective of this study is to evaluate the effect of an additional application of bonding resin on the bond strength of resin luting cements in both the light-cure (LC) and self-cure (SC) modes by means of the ${\mu}TBS$ tests. Three combinations of One-Step Plus with Choice, Single Bond with Rely X ARC, and One-Up Bond F with Bistite II were used. D/E resin and Pre-Bond resin were used for the additional application. Twelve experimental groups were made. Three mandibular $3^{rd}$ molars were used in each group. Indirect composite blocks were cemented on the tooth surface. $1\;{\times}\;1\;mm^2$ dentin-composite beam for ${\mu}TBS$ testing were made and tested. When total-etching dentin adhesives were used, an additional application of the bonding resin increased the bond strength (P < 0.05). However, this additional application didn't influence the bond strength of self-etching dentin adhesives (P > 0.05). In conclusion, the results suggest that an additional application of the bonding resin increases bond strength and enhances quality of bonding when using total-etching dentin adhesives.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.72-78
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• 1999

To accelerate the curing and to improve the bonding properties of urea-melamine-formaldehyde (UMF) resin adhesives for plywood, the effects of resin compositions and additives on gelation time and bonding strength were discussed. The gelation time of UMF resin prepared by simultaneous reaction with urea(U), melamine(M) and formaldehyde(F) at M/U molar ratio 0.2 was shortened as the molar ratio of formaldehyde to urea was increased. However, at F/U molar ratios higher than 2.5, the amounts of free fomaldehyde of resin could not satisfy with KS standard, Therefore, it was difficult to increase the amount of formaldehyde in resin composition for the purpose of fast gelation time. With increasing the molar ratio of melamine to urea(M/U) from 0.3 to 0.6 at constant F/U molar ratio 3.4, the gelation time of UMF resin was slightly decreased, while gradually increased at M/U molar ratio higher than 0.6. The gelation properties of UMF resin and bonding strength of UMF-bonded plywood could be enhanced by using ammonium chloride and p-toluene sulfonic acid as a curing-agent together with wheat flour and corngluten powder as a extender.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.61-67
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• 1997

The bending performances of sloped finger-joints in Pinus densiflora S. et Z. were tested in order to improve the strength properties of finger-joint Sloped finger-cut pieces were jointed with four kinds of adhesives(resorcinol-phenol, oilic urethane, polyvinyl acetate, and polyvinyl-acryl acetate resin). The slope ratios of finger joints were 0, 0.5, 1.0, 2.0. The MOE, MOR and defletion to maximum load in bending of sloped finger-joints and solid wood specimen were measured. The results were: 1. The efficiencies of MOE to finger and sloped finger-joints were 82% or greater in every kind of adhesives except polyvinyl-acryl acetate resin adhesive and there were some effect of slope on the MOE in a sloped finger-joint for polyvinyl-acryl acetate and oilic urethane resin adhesives. 2. The effects of slope on the MOR to sloped finger-joints were showed in every kind of adhesive, because the efficiencies of MOR increased with increasing slope ratio in sloped finger-joints. The efficiencies of MOR to slope ratios of 0 and 2.0 ranged 43~65% and 76~82%, respectively. There was almost no effect of the kinds of adhesives on the MOR to the slope ratio of 2.0. 3. It was found impossible to estimate the bending strength of sloped finger-jointed Pinus densiflora S. et Z. by using MOE. The correlation coefficient(0.124) between MOE and MOR was very low and not significant at 5% level.

• Journal of Conservation Science
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• v.37 no.3
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• pp.282-288
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• 2021

This basic research was conducted to support the development of woodcraft bio-adhesives using peach gum, which is the resin produced by peach trees. The synthesis conditions of these adhesives were optimized by performing 144 experiments. The application potential of peach gum adhesives was explored by comparing their properties with those of three natural adhesives and four synthetic adhesives. The best adhesive strength was obtained by dissolving the resin in 80 mL of distilled water containing 1.5 g NaOH, 1.65 g H₂O₂ ( pH 8.0-9.0), 0.5 g NaClO, and 0.5 g H₂BO₂. The adhesive strength, which showed minimal changes and excellent reversibility, was 125.39 kgf/cm². Ultraviolet radiation-mediated deterioration in strength in the absence of total aerobic bacteria was negligible (△E^*ab = 2.75). These data confirm the potential value of peach gum-based bio-adhesives for woodcraft as well as their utility as alternatives for natural and synthetic adhesives used for the manufacture and restoration of handicrafts and preservation of cultural assets.