유지요소의 크기와 형태가 간접복합레진과 금속간의 결합강도에 미치는 영향

이윤정,전영찬,정창모,Lee, Yun-Jung,Jeon, Young-Chan,Jeong, Chang-Mo 대한치과보철학회 2007 대한치과보철학회지 Vol.45 No.5

Purpose: The purpose of this study was to investigate the effect of sire and shape of retention element on the bond strength of indirect composite resin and metal. Material and method: The metal disk specimens, each 6mm in diameter, were cast from CrCo alloy. They were divided into 8 groups by applied retention element. retention bead group $B2\;({\phi}\;0.2mm),\;B4\;({\phi}\;0.4mm),\;B6\;({\phi}\;0.6mm),\;B8\;({\phi}\;0.8mm)$, retention crystal group C2 (0.2mm), C5 (0.5mm), C8 (0.8mm) and sandblasting group SB ($110{\mu}m\;Al_2O_3$ blasting) as control. Eighty-eight metal specimens were veneered with $TESCERA^{(R)}$ Indirect resin system. One specimen of each group was sectioned and the resin-metal bonding pattern at the interface was observed under measuring microscope. Other specimens were then tested for tensile bond strength on an Instron universal testing machine at a crosshead speed of 2mm/min. Results: 1. Compared to sandblasting, beads or crystals increased the resin-metal bond strength (P<.05). 2. 0.2mm retention crystals were most effective in improving the resin-metal bond strength (P>.05). 3. 0.2mm beads showed the highest bond strength among retention bead groups, but there was no statistically significant difference (P>.05). 4. Retention crystals tend to be higher in bond strength than retention beads due to wider surface area. 5. The larger retention element, the larger the undercut for the mechanical retention, but the gap at resin-metal interface was also increased. Conclusion: Within the limitations of this study, 0.2mm retention crystals were most effective in improving the resin-metal bond strength.

글리옥살 처리 면직물의 첨가제에 의한 백도 증진

신인수,김용태,이의소,Shin, In-Soo,Kim, Yong-Tae,Lee, Eui-So 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.5

Cotton fabrics were treated with glyoxal for a nonformaldehyde durable-press finish by a pad-dry-cure method. $MgCl_{2}/citric$ acid mixture or $Al_{2}(SO_{4})_{3}$ were used as a catalyst. The effects of additives such as sodium tetraborate decahydrate (STB), sodium peroxoborate tetrahydrate (SPB), and sodium chlorite (SC) were examined. The additives improved the whiteness and strength retention of the treated fabrics. SPB was superior to STB for the whiteness and strength retention. SC was better than either SPB or STB in the wrinkle recovery angles (WRA) and strength retention while the whiteness was similar to that of SPB or STB. SC was more effective for improving the whiteness and strength retention when it was used together with sodium phosphate monobasic.

Interpretation of Seam Property by Geosynthetics Bonding Method

전한용(Han-Yong Jeon),김원춘(Yuan-Chun Jin),이용준(Yong-Joon Lee),최용석(Yong-Suk Choi),백운일(Un-il Baek) 한국지반신소재학회 2012 한국토목섬유학회 학술발표회 Vol.2012 No.11

8 Geotextiles(; 4 woven and 4 nonwoven types), 4 geogrids and 2 geocomposites of [nonwoven/fibers/nonwoven] structure were used to compare the seam properties. Tensile strength retentions of these geosynthetics were evaluated as the degree of damage by chemical degradation. Woven geotextiles showed the higher seam strength in the order (SSd-1 < SSd-2) > (SSa-1 < SSa-2) > geospacer without regard to the design strength. For nonwoven geotextiles, the order of seam strength is geospacer > (SSa-1 < SSa-2). Geogrids showed the higher seam strength in the order of band > geospacers but reduction factors were increased in the order of band > geospacer without regard to the geogrid’s compositions. Finally, geocomposites showed the higher seam strength in the order of geospacer > (SSa-1 < SSa-2).

폐지와 감귤박 기반 토양피복재 제조 연구

이유진,신명석,김정은,권순화,성용주 한국펄프·종이공학회 2024 펄프.종이기술 Vol.56 No.1

Soil cover materials for the mulching has been used to regulate ground temperature, suppress weed growth, and retain moisture in the soil due to global warming. Plastic-based mulching materials are mainly used for soil covering, but there are related problems such as lack of water retention and control of the waste covering materials that pollute the soil. In this study, citrus pomace and waste paper were used to produce soil mulching material to contribute to resource recycling and the effects on water retention and compression strength were evaluated for functional evaluation. The addition of waste paper fibers to citrus pomace increased water retention property and compression strength. And the addition of the calcium oxide provided the increase in the strength properties and the control of pH.

Comparative evaluation of shear bond strength of orthodontic brackets bonded to three-dimensionally- printed and milled materials after surface treatment and artificial aging

Ameer Biadsee,Ofir Rosner,Carol Khalil,Vanina Atanasova,Joel Blushtein,Shifra Levartovsky 대한치과교정학회 2023 대한치과교정학회지 Vol.53 No.1

Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 μm aluminum oxide particles (SA) and aging; group B, sandblasted with 30 μm silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A–D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A–D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

온도조건에 따른 3D 프린팅 모르타르의 기초적 특성

유병현(Byung-Hyun Yoo),이동규(Dong-gyu Lee),박종필(Jong-Pil Park),황병일(Byoung-Il Hwang) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.9

3D 프린팅 모르타르는 온도에 따라 굳지 않은 모르타르의 레올로지 특성 및 경화 모르타르의 강도발현 특성이 변화되기 때문에 현장 온도를 고려하여 3D 프린팅 모르타르를 제조해야 작업성 및 압축강도 등을 확보할 수 있다. 기온이 낮은 동절기에는 모르타르의 경화속도가 늦어져 초기강도가 저하되는 문제가 발생되어 모르타르의 초기강도 확보를 위한 모르타르 배합을 조정하거나 초기강도 증진용 화학 혼화제를 적용하여 이를 개선해야 할 것이고, 기온이 높은 하절기에는 모르타르 수화반응 촉진에 기인해 모르타르 제조 후 시간이 경과함에 따라 모르타르 유동성 저하가 빠르게 진행되기 때문에 압송성 및 작업성이 저하되어 3D 프린팅 모르타르의 품질 문제가 발생할 수 있으므로 이를 대비해야 한다. 본 연구에서는 20 ℃ 환경을 기준으로 10 ℃ 저온 및 30 ℃ 고온에서의 3D 프린팅 모르타르의 기초적 특성을 평가하였는데, 저온환경에서 3D 프린팅 모르타르는 초기강도가 크게 저하되어 20 ℃ 환경의 약 17 % 수준의 압축강도를 나타내었다. 이에 초기강도 증진용 첨가제를 적용하여 초기강도 발현특성을 확인한 결과 초기강도 증진용 첨가제를 분체량 대비 2 % 사용 시 20 ℃ 환경과 비슷한 수준의 초기강도를 확보할 수 있었다. 한편, 30 ℃ 고온환경에서는 3D 프린팅 모르타르의 유동성 저하가 20 ℃ 환경보다 2배정도 빠르게 진행되었고, 고유지형 감수제의 사용으로 30 ℃ 환경에서 기존의 20 ℃ 환경 대비 동등 이상의 유지성능을 확보할 수 있었다. The rheological properties of a fresh mortar and the strength characteristics of a hardened mortar in 3D printing change a lot with the temperature. In a low-temperature environment, the hardening speed of the mortar is slowed, lowering the early strength. In an environment of high temperature, the hydration reaction of the mortar is accelerated, reducing the workability. In this study, the characteristics of a 3D printing mortar manufactured at both low and high temperatures were evaluated concerning a 20°C environment. The early strength of the mortar in the low-temperature environment was found to be about 17% of that of the 20°C environments. Accordingly, when 2% of the additive was used to improve the early strength, it equated to that of a 20℃ environment. On the other hand, in the high-temperature environment of 30℃, the slump loss of mortar progressed twice as fast as that of the 20℃ environments. Accordingly, while using a high-retention type water reducing agent, it was possible to achieve in a 30℃environment a maintenance performance that is similar to that of the 20℃ environment.

배수용 지오텍스타일의 환경노출조건에 의한 지속가능형 적용성 평가

안승재(Seung-Jae Ahn),오형선(Hyung-Sun Oh),이아람(A-Ram Lee),한지연(Ji-Yoen Han),전한용(Han-Yong Jeon) 한국지반신소재학회 2012 한국토목섬유학회 학술발표회 Vol.2012 No.11

In this study, PET spunbonded nonwoven geotextiles were used as filter media of PVD(Prefabricated Vertical Drainboard). 3.5% NaCl solution as an artificial seawater was applied to examine the long-term strength retention and reduction factor was determined from strength retention. Arrhenius models is applied to evaluate sustainable applicability of PET spunbonded nonwoven geotextiles at 25℃ is predicted.

Elastic gels based on flaxseed gum with konjac glucomannan and agar

양지수,김정훈,최영진,한정우 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.10

In this study, we prepared hydrocolloid gels inwhich flaxseed gum (FSG), konjac glucomannan (KGM),and agar (AG) were blended in different ratios for use as aviscoelastic food. The prepared hydrogels’ physicochemicalproperties were analyzed concerning their water solubilityindex (WSI), swelling power (SL), frequency sweepresults, and microstructures. As the FSG ratio decreased,the WSI value of the compound gel tended to increase. However, it showed a tendency to have a relatively high SPvalue and a low tan d value according to a specific KGM/FSG/AG mixing ratios (8:2:1.5 and 6:4:1.5). Throughmicrostructure analysis, the FKA821.5 sample showed arelatively small, monodispersed gel building structure,correlated with the rheological results. In conclusion, theFKA821.5 gel was determined to have good water retentioncapacity and high structural strength. These results areexpected to increase the applicability of FSG-based gellingagents in the food industry.

시멘트 유지형 임플란트 보철물의 유지력에 시멘트의 종류와 열순환이 미치는 영향에 관한 연구

조재호,정창모,전영찬,Cho Jae-Ho,Jeong Chang-Mo,Jeon Young-Chan 대한치과보철학회 2003 대한치과보철학회지 Vol.41 No.4

Statement of problem : In cemented implant-supported porstheses, it is still controversy what kind of cement to use. However, the effect of thermocycling on retentive strength of cemented implant-supported prostheses has not been well investigated. Purpose : This study was tested to evaluate the effects of various cements and thermocycling on retentive strengths of cemented implant-supported prostheses. Material and methods : Prefabricated implant abutments, height 5mm, diameter 6mm, 3-degree taper per side, with light chamfer margins were used. Ten specimens of two-unit fred partial denture were fabricated. The luting agents used for this study were three provisional luting agents which were Temp bond, Temp bond NE, IRM and four permanent luting agents which were Panavia F, Fuji-cem, Hy-bond Zinc cement, Hy-bond Polycarboxylate cement. 24 hours after cementation. the retentive strengths were measured by the universal testing machine with a cross-head speed of 0.5mm/min. Then cementation procedures were repeated and specimens were thermocycled 1000 times at temperature of $5^{\circ}C$ and $55^{\circ}C$. After thermocycling, the retentive strengths were measured. Results : Before thermocycling, the retentive strengths were decreased with the sequence of Panavia F. Fuji-cem. Hy-bond Zinc cement. Hy-bond Polycarboxylate cement, IRM, Temp bond NE and Temp bond, and there were significant differences among each groups(p<0.05). After thermocycling, the retentive strengths were decreased with the sequence of Panavia F. Fuji-cem, Hybond Zinc cement, Hy-bond Polycarboxylate cement, IRM, Temp bond NE and Temp bond, and there were no significant differences among Panavia F, Fuji-cem and Temp bond NE, Temp bond(p>0.05). The retentive strengths before and after thermocycling showed significant differences in Hy-bond Zinc cement. IRM, Temp bond NE and Temp bond(p<0.05). Conclusion : Within the limitation of this study, thermocycling do not affect the retentive strengths of permanent luting agents but the retentive strengths of temporary cements were reduced significantly after thermocyling.

Strength loss contributions during stages of heating, retention and cooling regimes for concretes

Yaragal, Subhash C.,Warrier, Jishnu,Podila, Ramesh Techno-Press 2015 Advances in materials research Vol.4 No.1

Concrete suffers strength loss when subjected to elevated temperatures during an accidental event such as fire. The loss in strength of concrete is mainly attributed to decomposition of C-S-H gel and release of chemically bound water, which begins when the temperature exceeds $500^{\circ}C$. But it is unclear about how much strength loss occurs in different stages of heating, retention and cooling regimes. This work is carried out to separate the total strength loss into losses during different stages of heating, retention and cooling. Tests were carried out on both Ordinary Portland Cement (OPC) based concrete and Ground Granulated Blast Furnace Slag (GGBFS) blended concrete for $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$ with a retention period of 1 hour for each of these temperature levels. Furnace cooling was adopted throughout the experiment. This study reports strength loss contribution during heating, retention and cooling regimes for both OPC based and GGBFS based concretes.