Magnesium hydroxide flame retardant and its application to a low-density polyethylene/ethylene vinyl acetate composite

Hyung Mi Lim,Joonho Yun,Mikyung Hyun,Yeomyoung Yoon,Dong Jin Lee,Sang Ok Jeong,Seung-Ho Lee,Chin Myung Whang 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4

Magnesium hydroxide as a halogen-free flame retardant attracts increasing attention due to environmental regulations and its unique physical properties such as non-toxicity and smoke suppressant ability during combustion. Low-density polyethylene/ethylene vinyl acetate(LDPE/EVA) blends are one of the polyolefins of which the flame retardance is enhanced by compositions containing magnesium hydroxide. Natural magnesium hydroxide flame retardant is available from the mineral brucite by the adjusting size distribution and surface treatment. A synthetic magnesium hydroxide is usually prepared by precipitation and hydrothermal treatment from magnesium salts or hydrolysis of MgO mineral(periclase). Natural and synthetic magnesium hydroxide have been prepared and mixed with LDPE/EVA by melt compounding. The dependence of the particle size and purity of the magnesium hydroxide and various additives for the synergistic effect on the flame retardance of LDPE/EVA has been studied through combustion tests of the polymer composites. The combustion behavior has been tested by limited oxygen index tests and the vertical burning tests of UL-94. Magnesium hydroxide as a halogen-free flame retardant attracts increasing attention due to environmental regulations and its unique physical properties such as non-toxicity and smoke suppressant ability during combustion. Low-density polyethylene/ethylene vinyl acetate(LDPE/EVA) blends are one of the polyolefins of which the flame retardance is enhanced by compositions containing magnesium hydroxide. Natural magnesium hydroxide flame retardant is available from the mineral brucite by the adjusting size distribution and surface treatment. A synthetic magnesium hydroxide is usually prepared by precipitation and hydrothermal treatment from magnesium salts or hydrolysis of MgO mineral(periclase). Natural and synthetic magnesium hydroxide have been prepared and mixed with LDPE/EVA by melt compounding. The dependence of the particle size and purity of the magnesium hydroxide and various additives for the synergistic effect on the flame retardance of LDPE/EVA has been studied through combustion tests of the polymer composites. The combustion behavior has been tested by limited oxygen index tests and the vertical burning tests of UL-94.

침전법을 이용한 Indium hydroxide 분말의 합성 연구

최은경,이원준,한규성,김응수,김진호,황광택,김종영,황해진,심광보,조우석,Choi, Eun-Kyoung,Lee, Won-Jun,Han, Kyu-Sung,Kim, Ung-Soo,Kim, Jin-Ho,Hwang, Kwang-Teak,Kim, Jong-Young,Hwang, Hae-Jin,Shim, Kwang-Bo,Cho, Woo-Seok 한국결정성장학회 2017 한국결정성장학회지 Vol.27 No.3

고밀도 ITO 타겟 제조를 위해 입자의 크기가 미세하면서도 응집성이 적은 $In_2O_3$ 분말을 합성해야 한다. 본 실험에서는 $In_2O_3$ 분말의 특성에 영향을 미치는 전구체 Indium hydroxide 분말의 크기와 형상을 제어하는 것에 목적을 두고 있다. 출발 물질로써 Indium metal을 질산($HNO_3$)과 증류수의 혼합용액에 용해시켜 $In(NO_3)_3$ 용액을 만들었다. 침전제로 수산화암모늄($NH_4OH$)을 사용하여 농도, pH, 온도가 Indium hydroxide 특성에 미치는 영향을 분석하였다. X-ray diffraction으로 각 시료의 결정상을 분석하고 Crystallite size를 계산하였으며, TEM으로 입자의 형상과 크기를 분석하였다. 그 결과 $In(NO_3)_3$ 농도가 증가할수록 얻어지는 Indium hydroxide의 입자크기는 증가하였고 일정한 농도의 $In(NO_3)_3$ 용액에서 침전 pH 변화에 따른 Indium hydroxide의 입자크기와 형상의 변화는 관찰되지 않았다. 침전 시 온도가 상승할수록 입자크기는 증가하였다. For the production of a high-density ITO target, $In_2O_3$ powders with a small particle size and low agglomeration should be synthesized. The purpose of this study is to control the size and shape of the Indium hydroxide precursor which affects the properties of the $In_2O_3$ powder. As a starting raw material, Indium metal was dissolved in a Nitric acid ($HNO_3$) solution. The effect of concentration, pH, and temperature on the properties of Indium hydroxide was investigated using ammonium hydroxide as a precipitant. Crystallite size of each sample was analyzed by X-ray diffraction and the shape and the size of the powder was analyzed by transmission electron microscopy. As a result, the particle size of Indium hydroxide was increased with increase in the concentration of $In(NO_3)_3$ and the particle size and shape of the Indium hydroxide remained unchanged with increase in the pH of the solution. The particle size increased with increase in the precipitation temperature during precipitation.

2P-200 Aqueous-Phase synthesis of hydroxide nanoplates and hydroxide/Pt and their electrochemical properties

정의영,최형석,유태경 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

We have successfully synthesized transition metal hydroxide (Ni(OH)2, Co(OH)2) nanoplates and transition metal layered double hydroxide nanoplates in an aqueous solution. In addition, we could attach Pt nanoparticles on the hydroxide nanoplates accociated with enhancement for electrochemical catalytic acitivity because of combination transition metal hydroxide and Pt. We could control the ratio of transition metal hydroxide to Pt. We have also measured excellent electrochemical catalytic performance compared to the commercial materials. The synthesized nanomaterials were characterized by using TEM, XRD and XPS. The synthesized nanomaterials have a uniform size and shape.

Fermentation characteristics of acid hydrolysates by different neutralizing agents

Seong, H.A.,Lee, J.S.,Yoon, S.Y.,Song, W.Y.,Shin, S.J. Pergamon Press 2016 International journal of hydrogen energy Vol.41 No.37

<P>Impact of cations in a fermentation broth by calcium, potassium, or sodium hydroxide was investigated. Acid hydrolysate from lignocellulosics is generally neutralized with calcium hydroxide, which is an insoluble salt (known as gypsum) produced in the process. Also, adsorption of monosaccharides on gypsum surface caused the loss of saccharide. To replace calcium hydroxide, potassium or sodium hydroxide which have high water solubility are used. More glucose was obtained by potassium hydroxide neutralization (glucose yield, 29.6 g) or sodium hydroxide neutralization (glucose yield, 38.9 g) than calcium hydroxide neutralization (glucose yield, 18.1 g) which shows less adsorption on the insoluble salt surface. In fermentation with three yeasts (Saccharomyces cerevisiae, Kluyveromyces marxianus, and Pichia stipitis), the sodium ion acts as an inhibitor and does not ferment the acid hydrolysate. However, acid hydroxide neutralized with potassium hydroxide was well fermented within 24 h with more ethanol production than that neutralized with calcium hydroxide. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Pulp Response of Mineral Trioxide Aggregate, Calcium Sulfate or Calcium Hydroxide

Yun, Young-Ran,Yang, In-Seok,Hwang, Yun-Chan,Hwang, In-Nam,Choi, Hong-Ran,Yoon, Suk-Ja,Kim, Sun-Hun,Oh, Won-Mann 대한치과보존학회 2007 Restorative Dentistry & Endodontics Vol.32 No.2

개의 치수에 MTA, calcium hydroxide 및 calcium sulfate로 치수복조 후 치수 반응을 서로 비교하여 MTA와 calcium sulfate가 임상적으로 치수복조제로서 사용 가능할 것인가를 구명하고자 본 연구를 시행하였다. 8개월 된 2마리 개의 24개의 치아가 본 연구에 사용되었다. 전신 마취하에 고속 핸드피스를 사용하여 멸균된 #2 round bur로 치경부에 와동을 형성한 후 치수를 노출시켰다. MTA, calcium hydroxide 및 calcium sulfate를 치수노출부에 도포하였다. 와동 부위는 IRM으로 가봉하고 광중합 레진으로 수복하였다. 처리 2개월 후, 전신 마취하에 희생시킨 후 조직학적으로 관찰하였다. MTA 처리군에서는 치수 노출부위에 경조직의 상아질교가 형성되었으며 새로 형성된 상아질교 하방에 조상아세포가 새로 형성되었다. 치수충혈과 함께 국소적인 혈관 증식이 나타났으며 치수에 염증반응은 나타나지 않았다. Calcium hydroxide로 처리한 군은 상아질교 하방에 조상아세포가 관찰되지 않았으며 만성염증반응이 다양하게 나타났다. Calcium sulfate로 처리한 군은 경조직의 상아질교가 관찰되었으며, 상아질교 하방에 조상아세포 층이 새로 관찰되었다. 몇몇의 중성구 침윤과 함께 미약한 정도의 만성염증반응이 관찰되었다. 이상의 결과에서 MTA가 calcium hydroxide 및 calcium sulfate에 비해 치수에 생체친화적임을 시사하며 기계적 치수노출시 치수복조제로 사용할 수 있음을 시사한다. This study was performed to verify the possibility of MTA and calcium sulfate as a pulp capping agent through comparing the dental pulp response in dogs after capping with MTA, calcium sulfate, and calcium hydroxide. 24 teeth of 2 dogs, 8 month old, were used in this study. Under general anesthesia, cervical cavities were prepared and pulp was exposed with sterilized #2 round bur in a high speed handpiece. MTA, calcium hydroxide, and calcium sulfate were applied on the exposed pulp. Then the coronal openings were sealed with IRM and light-cured composite. Two months after treatment, the animals were sacrificed. The extracted teeth were fixed in 10% neutral-buffered formalin solution and were decalcified in formic acid-sodium citrate. They were prepared for histological examination in the usual manner. The sections were stained with haematoxylin and eosin. In MTA group, a hard tissue bridges formation and newly formed odontoblasts layer was observed. There was no sign of pulp inflammatory reaction in pulp tissue. In calcium hydroxide group. there was no odontoblast layer below the dentin bridge. In pulpal tissue, chronic inflammatory reaction with variable intensity and extension occurred in all samples. In calcium sulfate group, newly formed odontoblast layer was observed below the bridge. Mild chronic inflammation with a few neutrophil infiltrations was observed on pulp tissue. These results suggest that MTA is more biocompatible on pulp tissue than calcium hydroxide or calcium sulfate.

수산화칼슘 근관충전제의 적용이 유치 치근상아질의 미세경도에 미치는 영향

전새로미,김종빈,유승훈 大韓小兒齒科學會 2013 大韓小兒齒科學會誌 Vol.40 No.3

수산화칼슘 근관충전제는 뛰어난 항균작용과 낮은 세포독성으로 우수한 유치 근관충전제로 평가되고 있다. 하지만 수산화칼슘을 근관 내 장기간 적용할 경우 치근 상아질에 미치는 부정적인 영향이 논의되고 있으며 많은 연구에서 영구치 근관에수산화칼슘을 적용 후 상아질 경도의 감소가 확인되었다. 본 연구에서는 수산화칼슘 제제의 적용 기간에 따라 유치 치근 상아질의 미세경도를 측정하여, 수산화칼슘의 적용이 유치치근 상아질의 미세경도에 미치는 영향을 평가하고자 하였다. 생리적 치근 흡수가 1/3이상 진행되지 않은 시기에 발거된 60개의 상악 유전치를 각각 20개 씩 대조군, 수산화칼슘과 요오드포름의 혼합제제(Vitapex, Neodent., Japan), 수산화칼슘과 증류수의 혼합제제를 적용하는 3개의 군으로 분류하였다. 각 치아는 같은 과정의 치수 절제술을 시행한 후 교정용 레진에 매몰하여 군당 5개 치아를 배정하고 24시간, 7일, 30일, 90일 후 치근 중앙부에서 2 mm 두께의 시편을 획득하여 비커스 미세경도 측정기를 통해 미세경도를 측정하였다. 측정된 미세경도 값은 Kruskal-Wallis test로 변수 간의 상호관계를 확인하였으며 사후 검정으로 Mann-Whitney test를 시행하였다. 시간에 따른 미세경도 값의 감소량은 선형 회귀분석을 통해 추이를 분석하였다. 수산화칼슘 근관 충전제가 유치의 치근 상아질의 미세경도에 미치는 영향을 조사한 결과, 다음과 같은 결론을 얻을 수 있었다. 수산화칼슘 근관 충전제를 유치의 근관에 적용 시 기간에 따라 치근상아 질의 미세경도가 감소하였으며, 이는 통계적으로유의하였다(p < 0.05). 수산화칼슘과 요오드화포름의 혼합제제에 비해 수산화칼슘을 증류수에 혼합하여 적용한 경우 유치 치근상아질의 미세경도가 더 급격하게 감소하였으며, 이는 통계적으로 유의하였다(p < 0.05). 수산화칼슘을 적용하지 않은 대조군에서도 7일, 30일, 90일 후 기간에 따라 치근상아질의 미세경도가 감소하였으며, 이는통계적으로 유의하였다(p < 0.05). Calcium hydroxide mixture medicaments can nearly be considered to be the ideal primary tooth filling material. However, long-term application of calcium hydroxide combinations as an intra canal medicament softens dentin. The aim of this study was to evaluate the effect of calcium hydroxide on the microhardness of root dentin of primary tooth. For the study, 60 extractedprimary incisors were divided into 3 groups (no medicament, calcium hydroxide/iodorform mixture, and calcium hydroxide/distilled water mixture). After the cleansing and shaping of canals, calcium hydroxide medicaments were applied and stored for different periods of time (1, 7, 30, 90 days). The root was horizontally sectioned into 2 mm thick specimens and the microhardness was measured using Vickers microhardness tester. The results were as follows :Root dentin microhardness of primary teeth decreased with long term exposure to calcium hydroxide medicaments according to the experimental period and showed statistically significance (p < 0.05). Root dentin microhardness of primary tooth filled with calcium hydroxide mixed with distilled water showed more decrease than filled with Vitapex and showed statistically significance (p < 0.05). Root dentin microhardness of a control group without exposure to calcium hydroxide decreased according to the experimental period and showed statistically significance (p < 0.05).

Nanostructured Ni-Mn double hydroxide for high capacitance supercapacitor application

( Rahul B. Pujari ),( Dong-weon Lee ) 한국센서학회 2021 센서학회지 Vol.30 No.2

Recently, transition-metal-based hydroxide materials have attracted significant attention in various electrochemical applications owing to their low cost, high stability, and versatility in composition and morphology. Among these applications, transition-metal-based hydroxides have exhibited significant potential in supercapacitors owing to their multiple redox states that can considerably enhance the supercapacitance performance. In this study, nanostructured Ni-Mn double hydroxide is directly grown on a conductive substrate using an electrodeposition method. Ni-Mn double hydroxide exhibits excellent electrochemical charge-storage properties in a 1 M KOH electrolyte, such as a specific capacitance of 1364 Fg^-1 at a current density of 1 mAcm^-2 and a capacitance retention of 94% over 3000 charge-discharge cycles at a current density of 10 mAcm^-2. The present work demonstrates a scalable, time-saving, and cost-effective approach for the preparation of Ni-Mn double hydroxide with potential application in high-charge-storage kinetics, which can also be extended for other transition-metal-based double hydroxides.

수산화마그네슘이 첨가된 저밀도 폴리에틸렌과 에틸렌 비닐 아세테이트 혼합물의 난연성

정영진 ( Yeong Jin Chung ),임형미 ( Hyung Mi Lim ),진의 ( Eui Jin ),오정규 ( Jung Kyoo Oh ) 한국공업화학회 2011 공업화학 Vol.22 No.4

수산화마그네슘이 첨가된 저밀도 폴리에틸렌-에틸렌 비닐 아세테이트 혼합물의 연소성을 시험하였다. 저밀도 폴리에 틸렌-에틸렌 비닐 아세테이트에 수산화마그네슘을 40∼80 wt% 첨가하여 용융 혼합하고 성형 후 콘칼로리미터(ISO 5660-1)를 이용하여 그의 연소성을 시험하였다. 수산화마그네슘을 첨가한 시험편은 첨가하지 않은 시험편에 비하여 그의 연소성이 감소하였다. 이것은 순수한 저밀도 폴리에틸렌-에틸렌 비닐 아세테이트에 첨가한 수산화마그네슘의 흡열 분해 때문에 연소 억제성이 향상된 것으로 생각된다. 수산화마그네슘을 첨가한 시험편은 첨가하지 않은 시험편 에 비해 낮은 최대열방출률과 낮은 유효연소열을 나타내었고, 수산화마그네슘 함량이 증가할수록 착화시간은 길어지 고, 최대열방출률은 감소하였다. It was performed to test the combustive properties of low density polyethylene and ethylene vinyl acetate (LDPE-EVA) mixture by the addition of magnesium hydroxide. Flame retardant of natural magnesium hydroxide was added to the mixture of LDPE-EVA in 40 to 80 wt% concentration. The composite was compounded to prepare specimen for combustive analysis by cone calorimeter (ISO 5660-1). Comparing with virgin LDPE-EVA, the specimens including the magnesium hydroxide had lower combustive properties. It is supposed that the combustion-retardation properties in the composites improved due to the endothermic decomposition of magnesium hydroxide. The specimens with magnesium hydroxide showed both the lower peak heat release rate (PHRR) and lower effective heat of combustion (EHC) than those of virgin polymer. As the magnesium hydroxide content increases, time to ignition increased and the peak heat release rate decreased.

Ni-Co hydroxide nanoneedles embedded in graphene hydrogel as a binder-free electrode for high-performance asymmetric supercapacitor

Hwang, Minsik,Kang, Jeongmin,Seong, Kwang-dong,Kim, Dae Kyom,Jin, Xuanzhen,Antink, Wytse Hooch,Lee, Chaedong,Piao, Yuanzhe Elsevier 2018 ELECTROCHIMICA ACTA Vol.270 No.-

<P><B>Abstract</B></P> <P>Ni-Co hydroxide nanoneedles embedded in graphene hydrogel are fabricated using an efficient two-step method and further explored as a binder-free electrode for high-performance asymmetric supercapacitors. First, freestanding graphene hydrogel is prepared via reduction in a mild condition. Second, Ni-Co hydroxide nanoneedles embedded in graphene hydrogel are obtained using a simple hydrothermal method. The existence of many hydrophilic functional groups in graphene hydrogel results in the generation of well-dispersed Ni-Co hydroxide nanoneedles throughout the graphene nanosheet. Moreover, the freestanding property of graphene hydrogel allows it to be used as a binder-free electrode, which can improve the energy density of the asymmetric supercapacitor without inhibiting its high power capabilities. The composite shows an excellent capacity of 544 C g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> in a three-electrode system. Moreover, the binder-free asymmetric supercapacitor achieves excellent performance with an energy density of 32.74 Wh kg<SUP>−1</SUP> at a power density of 320 W kg<SUP>−1</SUP> and good cycling stability with 85% capacitance retention at a current density of 10 mA cm<SUP>−2</SUP> after 5000 cycles. Therefore, the Ni-Co hydroxide nanoneedles embedded in graphene hydrogel have immense potential as electrochemically active materials for the development of high-performance supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni-Co hydroxide nanoneedles embedded in 3D graphene hydrogel were prepared by an efficient two-step method. </LI> <LI> The nanocomposite of Ni-Co hydroxide/graphene hydrogel was used as a binder-free supercapacitor electrode. </LI> <LI> The nanocomposite shows a high capacity of 544 C g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> in a three-electrode system. </LI> <LI> The asymmetric supercapacitor prepared by using the nanocomposite shows excellent power/energy density and cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The paper reported the Ni-Co hydroxide nanoneedles embedded in graphene hydrogel using facile two-step method. The asymmetric supercapacitor prepared by using the nanocomposite shows excellent energy density and cycling stability.</P> <P>[DISPLAY OMISSION]</P>

근관내 잔존 Calcium Hydroxide제재가 치근단 미세누출에 미치는 영향

신수일,조용범 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.1

The purpose of this in vitro study was to compare the apical leakage in extracted teeth filled with gutta-percha subsequent to dressing with one of three different calcium hydroxide preparations. Thirty six extracted teeth with single canal were sued in this study. After working length determination, canals were prepared with K flexo files to a #40 at the working length. Step-back flaring was produced by using #45, #50 K flexo files and #2, #3, #4 Gates Glidden burs. The teeth were randomly divided into 3 groups of 10 each: the remaining six teeth were used for negative and positive leakage control: Group 1, dressed with pure calcium hydroxide power (Sigma, USA) mixed with distilled water; Group 2, dressed with Metapaste (Metadent, Korea); Group 3, dressed with Vitapex (Neo Dental, Japan). Teeth were sealed with Caviton (GC, Japan) and incubated in 100% humidity, at 37℃ for 1 wk. All kinds of calcium hydroxide were removed from the canal with a MAF and 5% NaOCI. The canals were filled with AH-26 sealer and gutta-percha using lateral condensation technique, incubated in 100% humidity, at 37℃ for 2 days for the sealer to be set. The teeth were coated twice with nail varnish except for an area of approximately 2mm surrounding the apical foramen. All specimens were placed in 2% mthylene blue solution for 2 days. The root were sectioned longitudinally, the amount of apical leakage was measured to the most coronal part of the root canal to which the dye had penetrated. The independent measurements were made for each root using a stereomicroscope (x 40 magnification) and the average was recorded for statistical analysis. The results were as follows; 1.The mean of apical leakage in group of pure calcium hydroxide ranged 0.102±0.156mm, in Metapaste ranged 0.062±0.069mm, and in Vitapex ranged 0.067±0.072mm. 2.Group of pure calcium hydroxide exhibited more leakage than those of 2manufactured calcium hydroxide preparations, but it was not statistically significant. 3.Group of water-based Mtapaste showed lesser leakage than that of oil-based Vitapex, but it was not statistically significant.