• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.487-507
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• 1995

Composite resin repair requires strong bond strength between the new and old materials. The objective of the current study was to identify the optimal treatments for sufficient bond strengths. Bondings between same kinds of materials and cross bondings using chemical curing composites and light curing composites were tested. Surface treatments included the methods of sand-blasting, acid etching and coating of bonding agent. Seven kinds cases of combinations from three kinds of methods were experimented and compared with a control group of which surfaces were highly polished. Measurements of shear bond strength and observations of surface morphologic changes using a scanning electron microscope were done. Following conclusions were drawn : 1. The highest bond strength among composite resins were exhibited by the treatment of the sand-blasting and the coating of bonding agent. 2. Acid etched surfaces showed the lowest bond strength. Bond strengths obtained from experimental groups including acid etching were lower than those obtained from same kinds of experimental groups without acid etching. 3. Simple method of the coating of bonding agent produced the slightly increased bond strength on chemical curing composite and reduced bond strength on light curing composite. 4. Bonding surfaces of chemical curing composite resin showed slightly higher bond strengths than light curing composite resin, however significant differences were not confirmed statistically. 5. More significant irregular surfaces were created by sand-blasting method than acid etching method. 6. A principal component of fillers of both resins was silicon. Acid etching method produced the seperations and degradations of fillers, these were significant on light curing composite resins which containing barium fillers.

• 대한치과보철학회지
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• 제45권4호
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• pp.407-418
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• 2007

Purpose: The objective of this study was to evaluate the effects of hydrofluoric acid concentration & etching time on the shear bond strength between IPS Empress 2 ceramic and resin cement. Material and methods: Thirty three rectangular shape ceramic specimens($20{\times}12{\times}5mm$ size, IPS Empress 2 core materials) were used for this study. The ceramic specimens divided into ten experimental groups with three specimens in each group and were etched with hydrofluoric acid(4%, 9%) according to different etching times(30s, 60s, 90s, 120s, 180s). Etched surfaces of ceramic specimens were bonded with resin cement(Rely X Unicorn) using acrylic glass tube. All cemented specimens were tested under shear loading until fracture on universal testing machine at a crosshead speed of 0.5mm/min and the maximum load at fracture(kg) was recorded. Collected shear bond strength data were analyzed with one way ANOVA and Duncan tests. All etched ceramic surfaces were examined morphologically using SEM(scanning electron microscopy). Results: Shear bond strength of etching group$(35.89{\sim}68.01MPa)$ had four to seven times greater than no-etching group$(9.53{\pm}2.29MPa)$. The ceramic specimen etched with 4% hydrofluoric acid for 60s showed the maximum shear bond strength$(68.01{\pm}11.78MPa)$. Ceramic surface etched with 4% hydrofluoric acid for 60s showed most retentive surface texture. Conclusion: It is considered that 60s etching with 4% hydrofluoric acid is optimal etching methods for IPS Empress 2 ceramic bonding.

• 접착 및 계면
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• 제16권4호
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• pp.156-161
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• 2015

본 연구에서는 수분산 폴리우레탄 아크릴레이트의 접착력 및 물성을 향상시키기 위하여 polyester polyol, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), dimethylol propionic acid (DMPA), acrylate monomer를 사용하여 수분산 폴리우레탄 아크릴레이트를 합성하였다. 또한 합성된 수분산 폴리우레탄 아크릴레이트의 물성은 FT-IR, 입도분석, UTM, 접착력 등을 평가하였다. 입도 분석에서 아크릴산의 함량이 증가함에 따라 입자의 크기가 증가하였고, 기계적 물성을 평가한 결과, 아크릴산의 함량이 증가함에 따라 인장강도는 증가하였고 신율은 감소하였다. 접착강도는 PU/acryl 비율 중 acryl의 함량이 증가, 아크릴산의 함량이 증가할수록 증가하였다. 아크릴산의 함량이 0.5 wt%일 때 가장 높은 접착강도를 나타내었다.

• Elastomers and Composites
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• 제57권2호
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• pp.48-54
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• 2022

A polymeric adhesion promoter was synthesized to improve the adhesive strength of the Ni lead frame/epoxy composite. Poly(itaconic acid-co-acrylamide) (IAcAAM) was prepared by copolymerizing itaconic acid and acrylamide. We compared the adhesive strength between the Ni lead frame and epoxy composite according to the molecular weight of IAcAAM. The molecular weight of IAcAAM was controlled using an initiator, which made it possible to use IAcAAM in the epoxy molding compound (EMC) manufacturing process by modulating the melting temperature. The adhesive strength of Ni lead frame/epoxy composite increased with the addition of IAcAAM to the epoxy composite. In addition, as the molecular weight of IAcAAM increased, the adhesive strength of the Ni lead frame/epoxy composite slightly increased. We confirmed that IAcAAM with an appropriate molecular weight can be used in the EMC manufacturing process and increase the adhesive strength of the Ni lead frame/epoxy composite.

• 펄프종이기술
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• 제48권1호
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• pp.111-118
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• 2016

The effects of pulp beating degree and bulky promotor concentration on the properties of handsheet including a bulk and strength have been investigated during manufacturing of low density paper (high bulk paper) with cationic fatty acid bulky promotor. It was found that paper bulk increased with increasing cationic fatty acid bulky agent concentration, while tensile strength decreased. On the other hand the opacity of handseets also increased with increasing cationic fatty acid bulky agent concentration, while brightness decreased slightly. With increasing pulp beating degree, paper bulk as well as tensile strength increased, while opacity decreased. Brightness did not show a significant difference with increasing pulp beating degree. The highest bulk and strength values were observed when 1.5% (SwBKP) and 2% (HwBKP) of bulky promotor was treated into the 450 mL CSF pulp slurry.

• Advances in concrete construction
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• 제7권2호
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• pp.75-85
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• 2019

The present study is focused on the mechanical and durability properties of ternary blended cement concrete mix of different grades 30 MPa, 50 MPa and 70 MPa. Three mineral admixtures (fly ash, silica fume and lime sludge) were used as a partial replacement of cement in the preparation of blended concrete mix. The durability of ternary blended cement concrete mix was studied by exposing it to acids HCl and $H_2SO_4$ at 5% concentration. Acid mass loss factors (AMLF), acid strength loss factor (ASLF) and acid durability factor (ADF) were determined, and the results were compared with the control mix. Chloride ions penetration was investigated by conducting rapid chlorination penetration test and accelerated corrosion penetration test on control mix and ternary blended cement concrete. From the results, it was evident that the usage of these mineral admixtures is having a beneficiary role on the strength as well as durability properties. The results inferred that the utilization of these materials as a partial replacement of cement have significantly enhanced the compressive strength of blended concrete mix in 30 MPa, 50 MPa and 70 MPa by 42.95%, 32.48% and 22.79%. The blended concrete mix shown greater resistance to acid attack compared to control mix concrete. Chloride ion ingress of the blended cement concrete mix was low compared to control mix implying the beneficiary role of mineral admixtures.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• 대한치과보철학회지
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• 제45권5호
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• pp.589-600
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• 2007

Statement of Problem: Titanium has many advantages of high biocompatibility, physical porperties, low-weight, low price and radiolucency, but it is incompatible with conventional dental porcelain due to titanium's oxidative nature. Many previous studies have shown that they used the method of sandblast surface treatment prior to porcelain application, the researchs are processing about the method of acid etching or surface coating. Purpose: The purpose of this research is to study the effect on bond strength between titanium and porcelain when using macro-surface treatment and micro-surface treatment and macro and micro surface treatment. Material and method: In this study, we evaluated the bond strength by using 3-point bending test based on ISO 9693 after classified 7 groups-group P : polished with #1200 grit SiC paper, group SS : sandblasted with $50{\mu}m$ aluminum oxides, group LS : sandblasted with $250{\mu}m$ alumium oxides, group HC : treated with 10% hydrochloric acid, group NF : treated with 17% solution of fluoric acid and nitric acid, group SHC : treated with 10% hydrochloric aicd after sandblsting with $50{\mu}m$ alumium oxides, group SNF treated with 17% solution of fluoric acid and nitric acid. Results : Within the confines of our research, the following results can be deduced. 1. Group SS which was sandblasted with $50{\mu}m$ aluminum oxides showed the highest bond strength of 61.74 MPa and significant differences(P<0.05). The bond strengths with porcelain in groups treated acid etching after sandblasting decreased more preferable than the group treated with sandblasting only. It gives significant differences(P<0.05). 2. After surface treatments, the group treated with sandblasting showed irregular aspect formed many undercuts, in the SEM photographs. The group treated with hydrochloric acid had the sharp serrated surfaces, the group treated with the solution of fluoric acid and nitric acid had the smooth surfaces, the group with sandblasting and hydrochloric acid had irrigular and porous structure, the group with sandblasting and the solution of fluoric acid and nitric acid had crater-like surfaces. But all of the groups treated with acid etching was not found and undercut. Conclusion: In above results, average surface roughness increase, bond strength also increase, but surface topographs influences more greatly on bond strengths.

• Journal of Applied Biological Chemistry
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• 제66권
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• pp.90-97
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• 2023

The effect of citric acid on rice starch gelatinization and low-temperature (4 ℃) storage was studied in order to produce rice cake with a lower retrogradation rate. A citric acid solution in the ratio of 0, 0.5, 1.0, and 1.5% (w/w) of the water used during production was utilized. The gelatinization properties, gel strength, thermal properties, and texture analysis were evaluated to determine the retrogradation rate. The result showed that acid hydrolysis occurred in samples treated with citric acid. Thus, increasing citric acid decreased gelatinization temperature (58.63±1.98 to 45.84±1.24 ℃). The moduli of elasticity increased with increasing citric acid concentration, indicating an increased gel strength. Thermal analysis of starch showed that the onset, peak, and conclusion temperatures of retrogradation were increased significantly with the storage period and decreased with citric acid concentration. After 72 h of low-temperature storage (4 ℃), the retrogradation rate was lowest in the rice cake with 1.5% citric acid solution, with an increased ratio of 12.01 to 13.60% compared to the control sample, with a ratio of 12.99 to 43.54%. This shows a high retrogradation rate in the control sample. Additionally, sensory properties and retrogradation ratio suggest that the addition of 1.0% citric acid solution during rice cake production is efficient in retarding the retrogradation without an adverse effect on the rice cake modeling and acceptance.

• 한국의류학회지
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• 제11권1호
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• pp.63-69
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• 1987

Silk fibroin is likely to be hydrolyzed by acids or alkalies at high temperature, and the degree of the hydrolysis has been inferred from the changes in tensile strength and elongation. But, in this experiment, it was intended to infer that from the quantitative changes in terminal aminp group content as well as in tensile strength and elongation. Silk yarn was treated with boiling water, hydrochloric acid, and sodium hydroxide under various conditions. The boiling water somewhat degraded silk fibroin. Silk yarn treated with sodium hydroxide contained more terminal amino group than that treated with hydrochloric acid. This result agreed fairly well with the loss in weight, tensile strength, and elongation: the terminal amino group content increased with the decrease of tensile strength, elongation, and weight. The damage by sodium hydroxide to the silk fibroin was greater than that by hydrochloric acid.