• Polymer(Korea)
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• v.24 no.3
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• pp.326-332
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• 2000

The effects of sizing agent on the final mechanical properties of the glass fiber/unsaturated polyester composites were investigated by contact angle measurements at room temperature. In this work, glass fibers were coated by poly(vinyl alcohol), polyester, and epoxy type sizing agent and each property was compared. Contact angles of the sized glass fiber were measured by the wicking method based on Washburn equation using deionized water and diiodomethane as testing liquids. As an experimental result, the surface free energy calculated from contact angle showed the highest value in case of the glass fiber coated by epoxy sizing agent. From measurements of interlaminar shear strength (ILSS) and fracture toughness ( $K_{IC}$ ) of the composites, it was found that the sizing treatment on fibers could improve the fiber/matrix interfacial adhesion, resulting in growing the final mechanical properties. This was due to the enhanced surface free energy of glass fibers in a composite system.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.55-60
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• 2020

The recent semiconductor packaging technology is evolving into a high-performance system-in-packaging (SIP) structure, and copper-to-copper bonding process becomes an important core technology to realize SIP. Copper-to-copper bonding process faces challenges such as copper oxidation and high temperature and high pressure process conditions. In this study, the bonding interface quality of low-temperature copper-to-copper bonding using a two-step plasma treatment was investigated through quantitative bonding strength measurements. Our two-step plasma treatment formed copper nitride layer on copper surface which enables low-temperature copper bonding. The bonding strength was evaluated by the four-point bending test method and the shear test method, and the average bonding shear strength was 30.40 MPa, showing that the copper-to-copper bonding process using a two-step plasma process had excellent bonding strength.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.2
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• pp.139-145
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• 2012

There is a unique type of fatty acid in the hair surface. 18-methyleicosanoic acid (18-MEA) is an unusual anteiso fatty acid covalently linked to the outermost surface of hair cuticle. A layer of 18-MEA is located in the upper ${\beta}$-layer of the CMC that is responsible for the low surface energy and low friction resistance of the hair's outer surface. The high mobility of 18-MEA molecule facilitates spreading of extraneous lipid by decreasing interfacial shear strength. In this study, we introduced N-hydroxyl succinimidyl ester functional group to the one end of C10 - 40 isoalkyl acid for regenerating hair surface with covalently bound fatty acid layer. The re-hydrophobicization of hair surface has been investigated by contact angle measurement. The inner moisture content of hair at different levels of humidity (40, 55, 70 %RH) was measured by electric moisture analyzer. Treatment with Hydroxysuccinimidyl C10 - 40 Isoalkyl Acidate (HCIA) was supposed to make hair surface smoother by filling the cracks between cuticles with covalently bound fatty acid monomolecular layer like cuticle glue. This glue effect was also confirmed with line profile of AFM images. Therefore, the moisture and structural components of inner hair were not easily flown out and the optimum moisture content could be kept constantly though the outside humidity level was changed. The lateral force microscopy (LFM) by using atomic force microscope showed that the friction force of hair surface treated with HCIA was decreased. It also showed the constantly sustained friction value even after shampooing repeated 15 times.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.439-447
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• 2004

The purpose of this study was to investigate the influence of water, saliva and blood contamination on the bonding strength of metal brackets with a self-etching primer/adhesive to enamel. Ninety-six extracted human teeth were divided into four groups. The brackets were bonded to enamel with a self- etching primer (3M/Unitek Dental Products. Monorovia California) according to one of four protocols. The teeth were bonded in a dry condition (group D) or in contamination with distilled water (group W), artificial saliva (group S). or fresh human blood (group B) Shear bond strengths were tested using an Instron Universal testing machine. After debonding. bracket and tooth surfaces were examined with a stereomicroscope. In each group, four samples were selected and examined with a Scanning electron microscope of the prepared enamel surface and resin-enamel interlace. The results obtained were summarized as follows: Shear bond Strength if group D $(15.22{\pm}2.86MPa)$ and W $(15.20{\pm}3.85 MPa)$ Were higher than in group B$(12.56{\pm}2.94MPa)$ (p<0.05). There were no statistical differences in the shear bond strengths between groups D. W and S (p>0.05). There was a tendency to have less residual adhesive remaining on the enamel surfaces of group B than group D. The SEW morphology of group D and W showed a more roughened etching pattern than group S and B. Water or saliva contamination on bending of orthodontic brackets with Transbond plus self etching primer had almost no influence on bond strength In this study, the blood contaminated group showed the lowest bond strength, but it was above the clinically acceptable bond strength (5.9-7.8 MPa, Reynold, 1975). The results of this study suggest that acceptable clinical bond strengths can be obtained in wet conditions when self-etching adhesives are used.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.113-127
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• 2008

The purpose of this study was to evaluate effect of application of $ZirLiner^{(R)}$ and blasting treatments on shear bond strength of zirconia-veneered porcelain interface. 60 uncolored zirconia plates and 30 colored zirconia plates were fabricated and divided into nine groups of 10 according to blasting treatment such as as-ground, glass blasting and alumina blasting and zirliner application. Veneering porcelains were built up over the center of the treated zirconia ceramic surface using jig and fired according to the manufacturers' instructions. Each specimen was completely embedded in acrylic resin. The specimens were placed in a mounting jig and subjected to shear force by a universal testing machine. Load was applied at a crosshead speed of 0.5㎜/min until failure. Average shear strengths were analyzed with two-way analysis of variance and one-way analysis of variance and the Duncan's post-hoc test. The fracture surfaces of the failed specimens were examined by SEM. The obtained results were as follows: 1. Depending on surface treatment by blasting, the degree of roughness is revealed in the order of Glass-blasted, As-ground, and Alumnia-blasted. The roughness average of uncolored and colored zirconia ceramic were not significantly different from blasting treatments. 2. In uncolored zirconia ceramic, the shear bond strength were not significantly different from blasting treatments. However, the shear bond strength were significantly different from Zirliner application. 3. Used ZirLiner, mean shear bond strength of colored zirconia was lower than uncolored zirconia. Especially, mean shear bond strength of colored zirconia was quite low with alumina-blasting treatment. 4. SEM analysis showed that veneered porcelain failed in zirconia ceramic interface and there was no cohesive failure.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.4
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• pp.269-277
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• 2018

Purpose: This study examined the effects of glass infiltration treatments on the shear bond strength (SBS) between zirconia core and ultra low-fusing porcelain veneer. Materials and methods: The zirconia specimens were classified into 4 groups (n = 12): Untreated zirconia (group Z), zirconia coated ZirLiner (group ZL), glass-infiltrated zirconia (group ZG), glass-infiltrated and sandblasted zirconia (group ZGS). A cylinder of ultra low-fusing veneer porcelain was build up on each disk ($6mm{\times}3mm$). SBS was measured using a universal testing machine. Scanning electron microscope and Energy Dispersive X-ray spectroscopy were used to evaluate the surface of zirconia and failure pattern after SBS. Results: SBS value of group ZGS was significantly lower than that of other groups (P < .05). No significant differences were detected among group ZL, group Z and group ZG. Conclusion: Glass infiltration is not effective to the bond strength between zirconia and ultra low-fusing porcelain veneer. Sandblasting also dramatically decreased the bonding strength.

• Polymer(Korea)
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• v.36 no.5
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• pp.612-616
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• 2012

In this work, the effect of chemical treatments of multi-walled carbon nanotubes (MWNTs) on the mechanical interfacial properties of carbon fiber fabric-reinforced composites was investigated. The surface properties of the MWNTs were determined by acid and base values, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The mechanical interfacial properties of the composites were assessed by interlaminar shear stress (ILSS) and critical stress intensity factor ($K_{IC}$). The chemical treatments based on acid and base reactions led to a significant change of surface characteristics of the MWNTs, especially A-MWNTs/carbon fibers/epoxy composites had higher mechanical properties than those of B-MWNTs and non-treated MWNTs/carbon fibers/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.

• Restorative Dentistry and Endodontics
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• v.29 no.2
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• pp.170-176
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• 2004

Objectives : In the unique metal iris method. the developing interfacial gap at the cavity floor resulting from the cavity wall property during polymerizing composite resin might affect the nominal shear bond strength values. The aim of this study is to evaluate that the iris method reduces the cohesive failure in the substrates and the cavity wall property effects on the shear bond strength tests using iris method. Materials and Methods : The occlusal dentin of 64 extracted human molars were randomly divided into 4 groups to simulate two different levels of cavity wall property (metal and dentin iris) and two different materials ($ONE-STEP^{\circledR}$ and $ALL-BOND^{\circledR}$ 2) for each wall property. After positioning the iris on the dentin surface. composite resin was packed and light-cured. After 24 hours the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Fracture analysis was performed using a microscope and SEM. The data was analyzed statistically by a two-way ANOV A and t-test. Results : The shear bond strength with metal iris was significant higher than those with dentin iris (p＝0.034). Using $ONE-STEP^{\circledR}$, the shear bond strength with metal iris was significant higher than those with dentin iris (p＝0.005), but not in $ALL-BOND^{\circledR}$ 2 (p＝0.774). The incidence of cohesive failure was very lower than other shear bond strength tests that did not use iris method. Conclusions：The iris method may significantly reduce the cohesive failures in the substrates. According to the bonding agent systems. the shear bond strength was affected by the cavity wall property.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.406-412
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• 2015

Unidirectional carbon/carbon (C/C) composites were manufactured using phenolic resins as a precursor of the carbonized matrix throughout a one-step manufacturing process. Also, molybdenum oxide ($MoO_3$) and binder pitches were impregnated with phenolic resins to improve the bulk density and mechanical property of the C/C composites. In this study, the influence of $MoO_3$ and binder pitches on mechanical properties of the C/C composites were investigated by measuring flexural strength (${\sigma}_f$) and interlaminar shear strength (ILSS). The results show that the enhancement of interfacial adhesions between the fibers and matrix resins of the C/C composites with $MoO_3$ and binder pitches which led to the improvement of mechanical properties of the C/C composites. This indicates that the presence of $MoO_3$ and binder pitches in C/C composites can develop the graphite structure and increase the bulk density.

• Composites Research
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• v.28 no.4
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• pp.239-243
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• 2015

Recent studies regarding the properties of carbon nanotubes (CNT) have made remarkable progress in CNT fibers research. However no CNT fibers showed the properties of CNTs because CNTs in fibers have weak interfacial bonding with low shear modulus in the pristine form. Thus, it is upmost interest to develop and employ post-production treatments to the CNT fibers that would potentially improve their properties. In this study, post-treatments resulted in improvement of strength of CNT fibers up to 40%.