• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.356-361
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• 1996

Cure kinetics of diglycidyl ether of bisphenol A(DGEBA)/4,4'-methylene dianiline(MDA) with hydroquinone-phenyl glycidyl ether(HQ-PGE) as a reactive additive, which was preliminarily synthesized, was investigated by DSC and FT-IR analyses. Kissinger equation and Arrhenius' equation were used to calculate activation energy and pre-exponential factor. When HQ-PGE was added to DGEBA/MDA system, it reduced activation energy of system. When the 5 phr of HQ-PGE was added to DGEBA/MDA system, activation energy was 7.8 kcal/mol by FT-IR analysis and 11.3 kcal/mol by DSC, in comparison with the system without HQ-PGE, activation energy decreased about 30% and 9%, respectively. According to these results, HQ-PGE, introducing agent of this system, acted as a catalyst.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.904-909
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• 1994

Cure kinetics of DGEBA(diglycidyl ether of bisphenol A)/MDA(4,4'-methylene dianiline)/GN(glutaronitrile) system with and without HQ(hydroquinone) as a catalyst was studied by Kissinger equation and Fractional life method. The activation energy of the system with HQ was somewhat lower and the pre-exponential factor of that was higher by about 30% than those of the system without HQ. As 1.25phr of HQ was added, reaction rates increased about 1.8 times.

• Journal of the Korean Chemical Society
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• v.27 no.5
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• pp.353-360
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• 1983

The adsorption behavior of 8-hydroxyquinoline (8HQ) on Amberlite XAD-4 and-7 resins was investigated by measuring its distribution coefficients under various experimental conditions, such as shaking time, pH and concentration of methanol in the medium. The application of 8HQ-impregnated-XAD resins for the absorption and separation of metal ions was studied. The maximum adsorption of 8HQ on XAD resins was observed in the 30% methanol solution having pH range from 6.0 to 9.0. The impregnation capacities of XAD resins for 8HQ were 3.81${\times}$10-2mmol, 8HQ/g, XAD-4 resins and 2.60${\times}$10-2mmol, 8HQ/g, XAD-7 resin, respectively. The 8HQ-impregnated-XAD resins were stable in pH range from 6.0 to 10.0 and the amount of 8HQ leached from XAD-4 resin by eluting with hydrochloric acid(above 5M) was negligible. The optimum pH range for the adsorption of metal ions on 8HQ-impregnated XAD resin was also 6.0 to 10.0, and the adsorption mole ratio of metal ion to 8HQ were 1 : 2 for Cu(II), Cd(II) and Ni(II), and 1 : 3 for Fe(III) at the above pH range. It was found that the absorbed metal ions on 8HQ-impregnated-XAD resins were recovered quantitatively with 5M HCl and 8HQ-impregnated-XAD-4 resin could be reusable over 5 times without decrease in its impregnation capacity.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.731-736
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• 1994

Cure kinetics of DGEBA/MDA/MN system with and without HQ were studied by Fractional life method and Kissinger equation. And the effect of HQ as a catalyst was studied. As cure temperature increased, the reaction rate increased and reaction order was almost constant. The activation energy of the system with HQ was lower about 13% and the reaction rate was higher than that of the system without HQ. It was because hydroxyl group of HQ formed a transition state with epoxide group and amine group and opened the epoxide ring easily and rapidly.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.7
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• pp.992-997
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• 2002

Two in vivo experiments were conducted to evaluate the effect of novel urease inhibitor hydroquinone (HQ) on ammonia release rate from urea hydrolysis, nitrogen balance, nutrient digestibility and efficiency of microbial protein synthesis. In Exp. 1, twelve crossbred cannulated lambs were randomly assigned within initial body weight block to one of four HQ treatments, which included 0 (control), 30, 60 or 80 mg HQ/kg DM intake. Ammonia concentration and pH of ruminal fluid were immediately measured at 0, 2, 4, 6 and 8 h after feeding. Increasing the dose of HQ tended (p<0.15) to linearly decrease NH3 formation. The ammonia peak concentration (2 h post-feeding) in animals receiving HQ was approximately one-half of that in animals not receiving HQ (p<0.01), and a relatively sustained ammonia release could be obtained at the dose of 30 or 60 mg HQ/kg DM. In Exp. 2, sixteen intact crossbred lambs (weight $40{\pm}0.8kg$) were used in a $2{\times}2$ factorial design experiment. The four rations consisting of soybean meal-based (SBM) or urea-based (Urea) nitrogen source with or without HQ (S1, S0, U1 and U0) were fed in digestion and N balance trials. Apparent digestibility of major nutrients except that of ADF was not affected by either nitrogen source or addition of HQ. Regardless of nitrogen source, supplementation of HQ significantly improved ADF digestibility (p<0.05). The various ration had no effects on N metabolism in the presence of HQ. There was significant difference between total purine derivatives (PD), estimated efficiency of microbial N synthesis (p<0.05) and urea-N excretion (p<0.01) in the urine for the SBM ration and for the Urea ration. However, HQ had little influence on efficiency of microbial N synthesis as proportion of daily intake of total tract digestible OM (p>0.05). No interactions between main nitrogen source and HQ were measured throughout the trial. Results of this study suggest that addition of HQ to ration may improve ADF digestion with having no negative effect on N metabolism and microbial protein production.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.386-389
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• 1997

반응성 첨가제로 사용된 HQ-PGE가 DGEBA/MDA계의 기계적 성질에 미치는 영향을 살펴보기 위해서 충격강도와 인장강도를 측정하였다. HQ-PGE의 함량이 25phr일 때 충격 강도는 첨가되지 않았을 때보다 40% 증가하고, 인장강도도 약간 증가하였다. 이것은 HQ-PGE가 합성될 때 생성된 수산기가 자촉매 반응을 하면서 에폭시 수지의 미반응된 에폭시기와 반응한 결과로 사료된다. Young's modulus와 신장율은 HQ-PGE의 함량이 증가함에 따라 크게 변화하지 않았다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.151.2-151.2
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• 2010

본 연구는 하이드로퀴논(HQ)을 이용하여 매립가스로부터 이산화탄소를 선택적으로 분리하고 유기 크러스레이트 형태로 분리 및 저장에 적용하기 위한 연구로써 하이드로퀴논을 다양한 객체가스와 반응시키면서 열역학적 안정영역을 파악하고 분광학적 방법을 이용하여 미세구조 변화를 분석하고자 하였다. 먼저 ${\alpha}$-HQ를 고압(4MPa)의 이산화탄소와 반응시켜 이산화탄소가 포집된 ${\beta}$-HQ를 합성하였고, 동공 내에 존재하는 이산화탄소를 제거하여 동공을 유지하는 empty ${\beta}$-HQ를 만들었다. 온도를 증가시키면서 XRD 패턴을 측정한 결과 298 K 에서 378 K 사이에서 ${\beta}$-HQ 시료는 서서히 empty ${\beta}$-HQ 의 구조로 전환되었으며 378 K 이상의 온도에서 ${\alpha}$-HQ 구조로 급격히 전환되었다. 또한 생성된 empty ${\beta}$-HQ 동공에 이산화탄소가 포집, 해리되는데 있어서 온도의 영향을 확인하기 위해 298K과 343K의 온도에서 실시간 라만분광법으로 측정하였다. 그 결과 298K에서 약 200분의 시간이 지난 후 이산화탄소는 하이드로퀴논 동공 내로 포집되어 안정화되었으며 압력해방 후에는 빠져나가지 않고 동공 내에 존재함을 확인하였다. 그러나 343K에서는 급격히 포집되어 30분 이내 안정화되었고, 압력해방 후 동공 내에 존재하지 못하고 빠져나가는 것을 확인하였다. Empty ${\beta}$-HQ의 이산화탄소 선택도를 관찰하기 위해 이산화탄소와 메탄, 수소, 질소의 조성이 각각 30%, 30%, 20%, 20%인 혼합가스와 반응시킨 후 가스 크로마토그래프 분석을 실시한 결과, empty ${\beta}$-HQ내 포집된 가스 중 이산화탄소의 조성이 약 80% 이상으로 나타나 높은 선택도를 나타냄을 관찰하였다.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.517-523
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• 1994

The effects of cure kinetics and mechanism of DGEBA(diglycidyl ether of bisphenol A)/MDA(4,4'-methylene dianiline) with SN(succinonitrile) and HQ(hydroquinone) as an additive and accelerator were investigated. Cure kinetics was evaluated by Kissinger equation and fractional-life method through DSC analysis. The activation energy has hydroxyl group as an accelerator, the activation energy and the starting cure-temperature were lower than those of DGEBA/MDA/SN system. Cure mechanism of those systems was investigated through FT-IR according to the various SN contents. The ratio was SN : HQ = 4 : 1. It has been known that the cure reactions of an epoxy-diamine system are composed of primary amine-epoxy reaction, secondary amino-epoxy reaction and epoxy-hydroxyl group reaction. But in DGEBA/MDA/SN system, primary amino-CN group reaction and CN group-hydroxyl group reaction were added to the above mentioned reactions. These reactions attributed to the long main chain and the low crossliking density. And in DGEBA/MDA/SN/HQ system, hydroxyl group of HQ formed a transition state with epoxide group and amime group and also opened the ring of the epoxide group rapidly, then amino-epoxy reaction took place easily.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.667-672
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• 1995

Cure kinetics of DGEBA(diglycidyl ether of bisphenol A)/MDA(4, 4'-methylene dianiline)/SN(succinonitrile) system and DGEBA/MDA/SN/HQ(hydroquinone) system was studied by Kissinger equation and Fractional life method through DSC in the temperature range of 85∼150$^{\circ}C$. As cure temperature was increased, reaction rate increased and reaction order was almost constant. The reaction rate of the system with HQ as a catalyst was more higher and activation energy of that was lower about 20% than those of the system without HQ. Starting temperature of cure reaction for DGEBA/MDA/SN/HQ system decreased about 30$^{\circ}C$ than that of DGEBA/MDA/SN system.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.218-228
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• 2010

Components of dental resin-based restorative materials are reported to leach from the filling materials even after polymerization. Hydroquinone (HQ) is one of the major monomers used in the dental resin and is known as a carcinogen. Thus, carcinogenic risk of HQ leaching from the dental resin becomes a public health concern. The present study attempted to examine the carcinogenic potentials of HQ on the human epithelial cell, which is the target cell origin of the most of oral cancers. Cytotoxicity of HQ was observed above 50${\mu}M$ as measured by LDH assay, indicating a relatively low toxicity of this substance in human epithelial cells. The parameters of neoplastic cellular transformation such as cell saturation density, soft agar colony formation and cell aggregation were analyzed to examine the carcinogenic potential of HQ. The study showed that 2-week exposure of HQ showed the tendency of increase in the saturation density and the significant enhancement of soft agar colony formation at the highest dose, 50 ${\mu}M$ only. It is suggested that HQ has a weak potential of carcinogenicity. When cells were treated with HQ and TPA, a well-known tumor promoter, the parameters of neoplastic cellular transformation was significantly increased. This result indicates that the potential risk of carcinogenicity from HQ is largely dependent upon the presence of promoter. Exposure of 50 ${\mu}M$ HQ increased the time-dependent apoptosis as measured by the ELISA kit. This concentration coincides with a dose of neoplastic transformation, indicating a possible link between apoptosis and HQ-induced cellular transformation. Hydroquinone generated Reactive Oxygen Species (ROS) which was evidenced by the treatment of antioxidants such as trolox and N-acetyl cysteine and the GSH depleting agent, BSO. Antioxidants blocked the generation of ROS and the GSH depleting agent, BSO dramatically increased the ROS production. Since HQ is known to increase ROS production thru activation of transcriptional factor such as c-Myb and Pim-1, it is speculated that ROS generation by HQ plays a role in the activation of oncogene, which may lead to neoplastic transformation. In addition, ROS is involved in the alteration of signal transduction, which regulates the apoptosis in many cellular systems. Thus, ROS-mediated apoptosis may be involved in the HQ-induced carcinogenic processes. Protein kinase C (PKC) is known to play pivotal roles in neoplastic transformation of cells and its high expression is often found in a variety of types of tumors including oral cancer. PKC translocation of PKC-${\alpha}$ was observed following HQ exposure. Altered signaling system may also play a role in the transformation process. Taken together, HQ leached from the dental resin does not pose a significant threat as a cancer causing agent, but its carcinogenic potential can be significantly elevated in the presence of promoter. The mechanism of HQ-induced carcinogenesis involved ROS generation, apoptosis and altered signaling pathway. The present study will provide a valuable data to estimate the potential risk of HQ as a carcinogen and understand mechanism of HQ-induced carcinogenesis in human epithelial cells.