• Journal of the Korean Wood Science and Technology
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• v.34 no.6
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• pp.29-35
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• 2006

This stud y was conducted to investigate the bonding strength of plywood bonded with fatty acid-glycerol-pMDI adhesives with equivalent ratios of 1:1:2, 1:1:3, 1:1:4, 1:1:5, and 1:1:6. With veneer moisture contents of 0%, 3%, 5%, 8% and 15%, the bonding strengths exceeded the requirement of Korean plywood standard of $7.0kgf/cm^2$ with values of $13.7kgf/cm^2$, $11.6kgf/cm^2$, $11.2kgf/cm^2$, $9.8kgf/cm^2$, and $7.4kgf/cm^2$, respectively at fatty acid-glycerol-pMDI ratio of 1:1:2. With veneer moisture content of 30%, the bonding strengths exceeded th e requirement of Korean plywood standard of $7.0kgf/cm^2$, when fatty acid-glycerol-pMDI ratios were 1:6. Finally for satisfying the Korean plywood standard, the ratio of MDI in fatty acid-glycerol-pMDI should be increased with increasing of veneer moisture content.

• Advanced Composite Materials
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• v.16 no.1
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• pp.31-44
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• 2007

The purpose of this study is to improve the examining and understanding of the bonding behavior of Fiber Reinforced Polymer (FRP) sheets bonded to concrete blocks and steel plates under fatigue loading. First, a series of experimental investigations is summarized in the paper. The fatigue behavior of bonding surface between FRP sheets and concrete is finally characterized by the conducted P-S-N diagram representing the relationship among the probability of FRP debonding (P), the bond stress amplitudes (S), and the number of cycles (N) at debonding on a semi-logarithmic scale. The different debonding modes for various fracturing surface are also investigated and evaluated.

• Macromolecular Research
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• v.17 no.9
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• pp.631-637
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• 2009

This study examined the unique self-doping behavior of carboxylated polyaniline (PCA). The self-doped PCA was synthesized using an environmentally benign enzymatic polymerization method with cationic surfactants. XPS showed that HCl-doped PCA contained approximately 34% of protonated amines but self-doped PCA contained 9.6% of the doped form of nitrogen at pH 4. FTIR and elemental analysis showed that although the PCA was doped with the proton of strong acids at low pH via the protonation of amines, the self-doping mechanism of PCA at pH > 4 was mainly due to hydrogen bonding between the carboxylic acid group and amine group.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.26-39
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• 1999

Bis-GMA, the representative monomer of bonding resin, contributes to the rigidity of bonding layer. Hydrophilic monomer contributes to the permeability into dentin substrates while weaken the bonding layer due to its small molecular weight. The degree of conversion also contributes to the ultimate strength of the bonding layer. This study was performed for the correlation analysis of monomer ratio and dentin bonding strength via degree of conversion. 7 experimental bonding resins were prepared with Bis-GMA, ratio from 20% to 80% by 10% increment, and hydrophilic HEMA monomer. Their degree of conversion and shear bond strength to dentin were compared with Scotchbond Multi-Purpose adhesive, and the fractured surfaces were examined microscopically. The results were as follows; 1. The degree of conversion increased when, the ratio of Bis-GMA increased from 20% to 70%, whereas it decreased when the ratio of Bis-GMA was 80%. 2. Shear bond strengths of the experimental bonding resins of 80%, 70%, 60% ratio of Bis-GMA were significantly higher than those of the experimental bonding resin of 50% ratio of Bis-GMA and Scotchbond Multi-Purpose adhesive. Lower shear bond strengths were obtained with the experimental bonding resins of 40%, 30%, 20% ratio of Bis-GMA (p<0.05). 3. Adhesive fractures were associated with the bonding resins of the lower bond strength, while cohesive fractures within the bonding resin layer were associated with the bonding resins of higher bond strength. Bonding resins with shear bond strength higher than 18MPa showed some cohesive fractures within the composite resin or within the dentin. 4. Correlations between Bis-GMA ratio and the degree of conversion (r=0.826), between Bis-GMA ratio and shear bond strength (r=0.853), and between the degree of conversion and shear bond strength (r=0.786) were significant (p<0.05).

• Journal of Pharmaceutical Investigation
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• v.31 no.3
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• pp.173-180
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• 2001

The physicochemical characteristics such as glass transition temperature (Tg), surface energy, swelling and FT-IR of [P(AA-co-PEGMM)], a copolymer of acrylic acid (AA) and polyethyleneglycol monoethylether mono methacrylate (PEGMM), were evaluated. The Tg of [P(AA-co-PEGMM)] decreased with increasing PEGMM content. [P(AA-co-PEGMM)] with 18 mole% PEGMM had the Tg of about $40^{\circ}C$, the similar physiological temperature of human. Moreover, [P(AA-co-PEGMM)] with lower PEGMM content had higher hydration and expected lower mucoadhesive strengths. To predict the mucoadhesiveness of [P(AA-co-PEGMM)] films, the contact angle of films were measured. With the increasing content of PEGMM of films, the contact angle was increased and the higher mucoadhesive forces was expected. ATR-FTIR studies revealed that the addition of the PEG moiety in AA increased the potential of hydrogen bonding for [P(AA-co-PEGMM)] as compared to cross linking polyacrylic acid (cr-PAA) because the oxygen in the repeat unit of PEG contributed in the formation of hydrogen bonding in the presence of mucin solution.

• Macromolecular Research
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• v.15 no.7
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• pp.688-692
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• 2007

The hydrogen-bonding induced alternating multilayer thin films of dendrimers and block copolymer micelles were demonstrated. The block copolymer micelles derived from amphiphilic poly(2-ethyl-2-oxazoline)block-$poly({\varepsilon}-carprolactone)$ (PEtOz-PCL) in aqueous phase have a core-shell structure with a mean hydrodynamic diameter of 26 nm. The hydrogen bonding between the PEtOz outer shell of micelle and the carboxyl unit of poly(amidoamine) dendrimer of generation 4.5 (PAMAM-4.5G) at pH 3 was utilized as a driving force for the layerby-layer alternating deposition. The multilayer thin film was fabricated on the poly(methyl methacrylate) (PMMA) thin film spin-coated on silicon wafer or glass substrate by the alternate dipping of PEtOz-PCL micelles and PAMAM dendrimers in aqueous solution at pH 3. The formation of multilayer thin film was characterized by using ellipsometry, UV-vis spectroscopy, and atomic force microscopy. The PEtOz outer shell of PEtOz-PCL micelle provided the pH-responsive hydrogen bonding sites with peripheral carboxylic acids of PAM AM dendrimer. The multilayer thin film was reversibly removed after dipping in aqueous solution at $pH{\geq}5.6$ due to dissociation of the hydrogen bonding between PEtOz shell of PEtOz-PCL micelle and peripheral carboxyl units of PAMAM dendrimer.

• Carbon letters
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• v.16 no.3
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• pp.192-197
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• 2015

In the present work, we propose a molecule (C₁₄H₁₄) that can be used as a building block of hexagonal diamond-type crystals and nanocrystals, including wurtzite structures. This molecule and its combined blocks are similar to diamondoid molecules that are used as building blocks of cubic diamond crystals and nanocrystals. The hexagonal part of this molecule is included in the C₁₂ central part of this molecule. This part can be repeated to increase the ratio of hexagonal to cubic diamond and other structures. The calculated energy gap of these molecules (called hereafter wurtzoids) shows the expected trend of gaps that are less than that of cubic diamondoid structures. The calculated binding energy per atom shows that wurtzoids are tighter structures than diamondoids. Distribution of angles and bonds manifest the main differences between hexagonal and cubic diamond-type structures. Charge transfer, infrared, nuclear magnetic resonance and ultraviolet-visible spectra are investigated to identify the main spectroscopic differences between hexagonal and cubic structures at the molecular and nanoscale. Natural bond orbital population analysis shows that the bonding of the present wurtzoids and diamondoids differs from ideal sp³ bonding. The bonding for carbon valence orbitals is in the range (2s^0.982p^3.213p^0.02)-(2s^0.942p^3.313p^0.02) for wurtzoid and (2s^0.932p^3.293p^0.01)-(2s^0.992p^3.443p^0.01) for diamantane.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.369-378
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• 2018

The purpose of this study was to investigate the relationship between elderly people's consciousness of discrimination, elderly contact experience, grandparents' bonding, recognition of filial piety in College 190 Students and descriptive research study to identify factors affecting the sense of discrimination of the elderly. The questionnaire was collected from May 28 to June 15, 2018. The results of this study are as follows: First, the elderly's perception of the elderly was related to the elderly's contact experience (r = -. 353, p <.01), grandparent relationship with grandparents (r =. 01) were statistically significan. The influence factors of the elderly discrimination consciousness of college students are recognition of filial piety (${\beta}=-.354$, p<.001) and knowledge of the elderly (${\beta}=.281$, p <.001), the elderly contact experience and grandparents' bonding. The total explanatory power of the variables was 29.1%.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.125-129
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• 2021

We investigated the electronic property and atomic structure for chalcopyrite (CH) Al_xGa_1-xAs semiconductor by using first-principles FPLMTO method. The CH-Al_xGa_1-xAs exhibits a p-type semiconductor with a direct band-gap. For low Al concentration unoccupied hole-carriers are induced, but for high Al concentration it is formed a localized bonding or anti-bonding state below Fermi level. The hybridization of Al(3s)-Ga(4s, or 4p) is larger than that of Al(3s)-As(4s, or 4p). And the Al film on As-terminated surface, Al/AsGa(001), is more energetically favorable one than that on Ga-terminated (001) surface. Consequently, the band-gap of CH-Al_xGa_1-xAs system increases exponentially with increasing Al concentration. The change of lattice parameter is shown two different configurations with increasing Al concentration. The calculated lattice parameters for CH-Al_xGa_1-xAs system are compared to the experimental ones of zinc-blend GaAs and AlAs.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.216-227
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• 2007

Statement of problem: For the long-term success of removable partial dentures, the bonding between metal framework and denture base resin is one of the important factors. To improve bonding between those, macro-mechanical retentive form that is included metal framework design has been generally used. However it has been known that sealing at the interface between metal framework and denture base resin is very weak, because this method uses mechanical bonding. Purpose: Many studies has been made to find a simple method which induces chemical bond, now various bonding system is applied to clinic. In this experiment, shear bond strengths of heat-cured denture base resin to the surface-treated Co-Cr alloy were measured before and after thermocycling. Chemically treated groups with Alloy $Primer^{TM}$, Super-Bond $C&B^{TM}$, and tribochemically treated group with $Rocatec^{TM}$ system were compared to the beadtreated control group. The data were analyzed with two-way ANOVA. Result: 1. Shear bond strength of bead-treated group is highest, and Alloy $Primer^{TM}$ treated group, Super-Bond $C&B^{TM}$ treated group, RocatecTM system treated group were followed. Statistically significant differences were found in each treated group(p<0.05). 2. Surface treatment and thermocycling affected shear bond strength(p<0.05), however there was no interaction between two factors(p>0.05). 3. Shear bond strengths of bead-treated group and Alloy $Primer^{TM}$ treated group showed no statistically significant difference before and after thermocycling(p>0.05), and those of Super-Bond $C&B^{TM}$ treated group and $Rocatec^{TM}$ system treated group showed statistically significant difference after thermocycling(p<0.05).